Help Tires too big for my drive train?

[ColoradoDerek]

Hello.
I have a 1976 CJ5 and I was told I have an AMC20 axle on the back of my jeep and I'm still not sure what I have in the front. I went to a local jeep club meeting and tried to meet people (or a person) who would come check out my Jeep but didn't get good reception at first but I'll keep trying with those guys.

One thing I did learn was about the AMC20 and this guy (who kept laughing at me, it was quite the experience to listen to this guy just treat me like , but whatever) told me that the 35 " tires I have on my jeep are too big for the AMC20 axle and that it will snap it. He said that I need to change out my axles.

So, my question(s) are 1) is that right? Will it break my axles if I'm just driving around on trails? or is that only if I try to do some "rock crawling" type stuff? My 2nd question (2) is would I be smarter to lower my tire size, or buy new axles. I was briefly told that I can find an old truck and just use their axles but how hard is that conversion? what axles/trucks are compatible with my jeep? Do i need to replace all of them or just the rear ones? was this guy just being extreme because I was new?

My goals with this jeep are pretty easy. I just want to drive it around on trails. no rocks, no hill climbs, nothing that a person on a peddle bike couldn't also do. That's it. I WILL upgrade later when I want to do harder stuff but right now, I just want to get my Jeep to where it will do what I want, without fear of breaking down and someone telling me I'm going to snap an axle is a lot of fear of that.

I can take pictures if that will help someone help me. What I'm trying to get from these guys (here in town) is someone who can come hang out and tell me "yeah this part is shot, you need a new one of these, this isn't going to work" etc. Everyone seems to think this is a hard question??? I don't know why its proving to be challenge to get this answered for me.

Until I can find someone in "real life" to help me, I'm going to keep coming back here because you guys have been extremely helpful.

Other issues I'm having is dry rot on all the rubber around since the jeep sat for ~10 years (semi-covered) before I got it. Things like, motor mounts, look dry rooted and other things like that. How important is it to get those replaced? are they just dry rotted on the outside and the insides are likely still doing okay?

I have a bunch of questions like that one. Basically, I want to point to things that I think look possibly bad or maybe need replaced and someone can be like "nope, that's fine" or "yes,that is looking rough" If someone wants to do that picture by picture with me I'd appreciate it but I figure folks online won't really want to spend that kind of time which is why I'm after someone locally!

Maybe one of you live near Colorado and wanna get together at some point? I can provide food/beer!

Anyway, for now, I'm mostly concerned about my axles and my tire size. Trying to figure out how to move forward with that. Both options (buying smaller tires or buying a "trash" truck to steal its axles) are something I'm able to do I just want to know what the best option is. One other thing to consider is, I currently am running an AMC 360 motor (which these folks here said was still a good engine) but I'm wanting to switch it to a SBC 350. With that goal in my future, would it be better to find some beater truck with a SBC 350 in it and just get its axles/motor/transmission/etc and do the swap? In case you are wondering, I want to switch to the Chevy 350 because spare parts/engines/etc seem to be more available than AMC 360 parts. this guy who was laughing at me for not knowing anything said that "amc 360 parts are a dime a dozen" but I haven't been able to prove that anywhere.

Thank you for reading and for any help.
Again, I can get any pictures that anyone needs to help. If someone wants to possibly help me more in depth, I can give you my phone number, Facebook info, etc and we can do whatever you need to help me.

I just want to get out and drive this jeep but every time I think I'm close, some other nonsense happens. For example, all my rubber fuel lines are leaking now (after 3 months of driving it around with no issues). My front tie-rod is bent towards the front so no-one has been able to tell me how that happened (just randomly bent when was turning the wheel it seems).

I know these things are money pits but I thought it would be upgrading it! not having random weird things happen. anyway, thank you!!!!!

 

[NP435]

That rear end may have the 2 piece axle shafts and the housing isn't all that strong. The front end should be a Dana 30 again not all that strong. Some say you can truss and sleeve the axle tubes and upgrade the shafts and all is well. I chose Currie Dana 44's front and rear , chrome moly shafts, 35 spline Detroit True Tracs in both. The cost is shocking so do some research before jumping in. Budget and use define the end game. Tie rods in my experience don't just bend takes some effort and impact. i would run 35's on my jeep if the gearing was at least4.10 and lower would be better I think. I have 33's and 3.73 now. it works pretty ok even so 4.10 would be better. I am about 130 miles north of the colo/wyo line so pm me and we might be able to get together depends on my work schedule.

 

[j6824]

A lot depends on what you intend to do with it, and how you drive it in doing so.

Like NP said, the 20 can be shored up, and can actually match if not exceed the capability of a 44 (bigger ring gear). Truss, welded tubes and one piece shafts. Not too tough nor excessively expensive. Probably be worth considering with the 360 regardless of wheeling style.

Knowing your gear ratio would be a good thing.

Based on what you say you're looking to do, the SBC swap is going to be not only overkill, but expensive and labor intensive. You'll be looking at swapping both axles plus possibly tranny/tc (depending on what you have) as well. Might be a rabbit hole you may not wanna go down...not at this point, anyway.

I'm not aware of the scarcity of any 360 parts...others may chime in to the contrary. I can't recall hearing anything about that, though.

As far as the other components you mention, much depends on what's already been done by a previous owner, how it's been treated and stored, It would be a good idea to get somebody to lay eyes on it (several members from CO that are super good).

Sooner rather than later would be ideal...some of this stuff can be a bit of a safety issue (front end parts, leaking fuel lines) that you don't need to take a chance on.

If tires were included in the 10-year dry rot hibernation period, I'd strongly suggest you consider replacement, at which time you always could bump down to 33s if you were worried about the size.

 

[Techlight]

First off: Welcome to the forum!

Agree with the responses so far...and like everything cost is a factor

There's a lot to 35's than just the axles. That's a lot of weight to turn. Steering mount and linkage comes to mind as well frame stress. And what gearing you have is going to matter. The better your gearing the less stress you have on the drive train spinning those big tires. There are stronger axles than the 30 and the 20 but you can build them to take some abuse. If you're going to go out and beat the snot out of it that's a different story.

Leaking fuel lines should be number one on your list. It's not the safest way to drive around and it would suck if your new project went up in flames.

If your seeing dry rot on all the rubber it's most likely shot all the way through. I'd make this number two on my list.

Third would be to try to find a different group of local people to hang out with (or at the very least politely ignore that guy you described). If they're giving you day one, laughing at you, and not being helpful it doesn't sound like a good group. Most Jeep people and 4 wheelers in general are usually nice folks who will help you out. If you caught 80 percent of the folks on this forum and some gathering and asked anyone of us to go look at your rig we'd walk to the parking lot with you. Hell, if you saw my rig at the grocery store and said Hi can you look at my CJ5 I would.

All that being said if your rig is stock with poor gearing and someone tossed 35's on it you can probably expect some problems down the road.

Personally I'd keep the AMC motor but that's me. It's already in there and it's a good motor. Depends on if it's causing you any trouble. Swapping in an entire new drivetrain has it's own share of troubles and costs.

Not sure how new you are to the forum (you need a certain amount of posts before you can post pics)... but my other advice is to post up some pics on this thread of what you mentioned in your original post (pics of the axles, fuel lines, body bushings, motor/tranny mounts) and I'm sure folks will chime in. If you need specific advice on other issues place a new post with pics.

We'll help you out as far as we can and there's a ton of folks with decades of Jeep experience on here.

Again...Welcome.

 

[ColoradoDerek]

That rear end may have the 2 piece axle shafts and the housing isn't all that strong. The front end should be a Dana 30 again not all that strong. Some say you can truss and sleeve the axle tubes and upgrade the shafts and all is well. I chose Currie Dana 44's front and rear , chrome moly shafts, 35 spline Detroit True Tracs in both. The cost is shocking so do some research before jumping in. Budget and use define the end game. Tie rods in my experience don't just bend takes some effort and impact. i would run 35's on my jeep if the gearing was at least4.10 and lower would be better I think. I have 33's and 3.73 now. it works pretty ok even so 4.10 would be better. I am about 130 miles north of the colo/wyo line so pm me and we might be able to get together depends on my work schedule.

I am probably 8 hours away from you, guessing you are around Casper, WY or somewhere close to that. I'm unfortunately on the western side of CO and not the Denver side.

I also unfortunately do not know what my gearing ratio is. Is that something that is easy to figure out? or does it require tearing apart something and counting the teeth.

 

[ColoradoDerek]

A lot depends on what you intend to do with it, and how you drive it in doing so.

Like NP said, the 20 can be shored up, and can actually match if not exceed the capability of a 44 (bigger ring gear). Truss, welded tubes and one piece shafts. Not too tough nor excessively expensive. Probably be worth considering with the 360 regardless of wheeling style.

Knowing your gear ratio would be a good thing.

Based on what you say you're looking to do, the SBC swap is going to be not only overkill, but expensive and labor intensive. You'll be looking at swapping both axles plus possibly tranny/tc (depending on what you have) as well. Might be a rabbit hole you may not wanna go down...not at this point, anyway.

I'm not aware of the scarcity of any 360 parts...others may chime in to the contrary. I can't recall hearing anything about that, though.

As far as the other components you mention, much depends on what's already been done by a previous owner, how it's been treated and stored, It would be a good idea to get somebody to lay eyes on it (several members from CO that are super good).

Sooner rather than later would be ideal...some of this stuff can be a bit of a safety issue (front end parts, leaking fuel lines) that you don't need to take a chance on.

If tires were included in the 10-year dry rot hibernation period, I'd strongly suggest you consider replacement, at which time you always could bump down to 33s if you were worried about the size.

Thank you for the reply. Yes there were a lot of seemingly knowledgeable and nice guys at the meeting too but I guess no one wants to help the noob. I can respect that. If you are a veteran in your field it can be frustrating trying to talk to someone who is like me and doesn't know the names of things or really anything about Jeeping. Hard to get my feet wet so far though! Usually the internet is my go-to source of all knowledge but this time around, I really think someone seeing it in person will be 1000x more helpful than me trying to explain everything (that I know nothing about) on here (lol!!) but I do what I gotta do.

I have shelfed the jeep so to say until all these issues get fixed. it wont drive again for a while I'm sure. ESPECIALLY with the dry rotted fuel lines (LOL!!) The tires were also dry rotted but 2 of them were replaced by the person selling the jeep and the other 2 are still on there and I intended to buy them but yeah, now I'm not even sure what tire size to get because my axles are too weak (maybe).

When you say the SBC swap would be expensive, lets just forget about the engine and tranny for now but is it "hard" or does it require welding to swap out the axles for another set of axles? I'm not interested in anything that requires welding and if i have to go down to 20" tires to avoid welding then I will. I don't know, this seems like a difficult question. I'll try to do some research on axle swaps and see what it entails.

Thanks again.

 

[ColoradoDerek]

First off: Welcome to the forum!

Agree with the responses so far...and like everything cost is a factor

There's a lot to 35's than just the axles. That's a lot of weight to turn. Steering mount and linkage comes to mind as well frame stress. And what gearing you have is going to matter. The better your gearing the less stress you have on the drive train spinning those big tires. There are stronger axles than the 30 and the 20 but you can build them to take some abuse. If you're going to go out and beat the snot out of it that's a different story.

Leaking fuel lines should be number one on your list. It's not the safest way to drive around and it would suck if your new project went up in flames.

If your seeing dry rot on all the rubber it's most likely shot all the way through. I'd make this number two on my list.

Third would be to try to find a different group of local people to hang out with (or at the very least politely ignore that guy you described). If they're giving you day one, laughing at you, and not being helpful it doesn't sound like a good group. Most Jeep people and 4 wheelers in general are usually nice folks who will help you out. If you caught 80 percent of the folks on this forum and some gathering and asked anyone of us to go look at your rig we'd walk to the parking lot with you. Hell, if you saw my rig at the grocery store and said Hi can you look at my CJ5 I would.

All that being said if your rig is stock with poor gearing and someone tossed 35's on it you can probably expect some problems down the road.

Personally I'd keep the AMC motor but that's me. It's already in there and it's a good motor. Depends on if it's causing you any trouble. Swapping in an entire new drivetrain has it's own share of troubles and costs.

Not sure how new you are to the forum (you need a certain amount of posts before you can post pics)... but my other advice is to post up some pics on this thread of what you mentioned in your original post (pics of the axles, fuel lines, body bushings, motor/tranny mounts) and I'm sure folks will chime in. If you need specific advice on other issues place a new post with pics.

We'll help you out as far as we can and there's a ton of folks with decades of Jeep experience on here.

Again...Welcome.

I will have to get some more pics and get some more specific questions to ask. It is sounding more and more like someone took a stock CJ5 and just lifted it and put tires on it. That is FINE I guess, but definitely is annoying for me. at least I learned all of this before breaking it too much.

Just to be clear, I'm NOT driving it at all since I noticed the fuel lines leaking. (they are leaking on top of the engine, not like, underneath).

The guys I met weren't all laughing at me, just the one guy and his buddy who actually talked to me. I get the feeling most of these guys are GOOD guys and just didn't want to deal with the noob.

Either way, I'll get some more specific information and get some new posts up. I'm not interested at all in welding so unless that is an easy thing a shop can do or I can find instructions on how to do it to provide to them (the reinforcement of the axles) I'll either be getting new axles or smaller tires.

 

[CJ]

I also unfortunately do not know what my gearing ratio is. Is that something that is easy to figure out? or does it require tearing apart something and counting the teeth.

Try this post... https://jeep-cj.com/community/threads/how-to-determine-your-gear-ratio.10217/

 

[RiverandSand]

I agree with what was said sofar, if the AMC20 is stock it will have 2 piece axles, meaning it's an splined axle shaft with a hub attached by a big nut, it should have dust caps on the end of the axles covering the nut. The rearend will have double letter code stamped in the housing just right of the cover near the axle tube and will id the original gear ratio.
The AMC20 gets a bad rap, because of the weak axle tubes and 2 piece axles (all can be fixed), also this same axle came in the AMX and Javelin with a 360/401.
As said above you need to find new jeep people, sounds like a bunch of mall crawlers to me. No true jeepers or offroaders for that matter would laugh at a new jeeper wanting to know about their jeep.

 

[NP435]

I agree with what was said sofar, if the AMC20 is stock it will have 2 piece axles, meaning it's an splined axle shaft with a hub attached by a big nut, it should have dust caps on the end of the axles covering the nut. The rearend will have double letter code stamped in the housing just right of the cover near the axle tube and will id the original gear ratio.
The AMC20 gets a bad rap, because of the weak axle tubes and 2 piece axles (all can be fixed), also this same axle came in the AMX and Javelin with a 360/401.
As said above you need to find new jeep people, sounds like a bunch of mall crawlers to me. No true jeepers or offroaders for that matter would laugh at a new jeeper wanting to know about their jeep.

I am with you we can learn from others and why not help if we can, my last CJ7 had factory 1 piece shafts in the AMC20 found when the axle seals failed you know the rest of that story (cussing and a brake job too)

 

[NP435]

I am probably 8 hours away from you, guessing you are around Casper, WY or somewhere close to that. I'm unfortunately on the western side of CO and not the Denver side.

I also unfortunately do not know what my gearing ratio is. Is that something that is easy to figure out? or does it require tearing apart something and counting the teeth.

I think most of the questions are covered so I wont, 8 hrs is lot of travel by CJ via Denver lol.

 

[ColoradoDerek]

Try this post... https://jeep-cj.com/community/threads/how-to-determine-your-gear-ratio.10217/

I am going to be taking off my diff cover! yay! Hopefully I can find a stamp rather than counting. Anyway, hopefully can do that sooner than later.

What other "critical" pieces of information would you and the other wonderful folks here on the forums need to help me get my answers? Can I take pictures of the transmission, the gear shifter box, the axles, the drive train, etc, to get more help? or is it still going to be best for someone to see it in person.

I guess the best starting point is to actually know what I have!?

Thanks!

 

[Masscj7]

First off, welcome!

Next, read, read, read. You’ll be amazed how much you’ll learn by spending several hours just cruising the forums, there’s over 10 years of post and info. And you’ll never be mocked or feel uncomfortable just absorbing all the info.

Next, I would say after the immediate safety stuff is addressed, is set forth a good plan. I’m halfway through a full frame off and find that sometimes I jumped to a course of action that a year later I wish had done something different. Research and read, I find, dang, I didn’t know about that mod, wish I had knew prior to doing x,y,z.

As far as stock drive train, estimate your costs and do exactly what you have been doing. Really determine how you’re going to use and what’s your budget threshold. Everyone wants Currie axles, most can’t afford. Look at my build thread, I trussed my AMC20 and did one piece axles and way cheaper. For my use, real light trail and road, it’ll be fine. As for front end, unless you’re really hammering, how often are you using 4 wheel drive if mostly surface roads? Maybe some better axle shafts, but swapping whole axles is lots of work.

Lastly, don’t get sucked into the bigger is better trap. We share all different levels and budgets of rigs and it’s real easy to see someone post some awesome upgrade and we jump right away and say we have to have it! Who doesn’t want the shiniest and best, but end of day maybe way overkill for your use of rig and budget.

I can’t stress enough reading. I remember taking two full weekends to read some of the big build threads here (Gert and Shum’s are amazing) and you’ll be so much further educated.

Again, welcome


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[Masscj7]

And one of my biggest regrets is I didn’t do rear disc brake upgrade while axles were out and sand blasted before all reassembled and epoxy painted. Grrrr


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[CJ]

I am going to be taking off my diff cover! yay! Hopefully I can find a stamp rather than counting. Anyway, hopefully can do that sooner than later.

What other "critical" pieces of information would you and the other wonderful folks here on the forums need to help me get my answers? Can I take pictures of the transmission, the gear shifter box, the axles, the drive train, etc, to get more help? or is it still going to be best for someone to see it in person.

I guess the best starting point is to actually know what I have!?

Thanks!

This is great info.

-->> https://jeep-cj.com/community/forums/technical-threads.99/
-->> https://jeep-cj.com/community/#jeep-cj-comprehensive-database.176

 

[Techlight]

I am going to be taking off my diff cover! yay! Hopefully I can find a stamp rather than counting. Anyway, hopefully can do that sooner than later.

What other "critical" pieces of information would you and the other wonderful folks here on the forums need to help me get my answers? Can I take pictures of the transmission, the gear shifter box, the axles, the drive train, etc, to get more help? or is it still going to be best for someone to see it in person.

I guess the best starting point is to actually know what I have!?

Thanks!

Removing the diff cover and checking the stamps and/or counting teeth is the most accurate way to do it. There are other ways but that works too. I'd do the front since it will be the same. The 30 is easier to seal back up than the 20.

Definitely post some pics up...we can help you ID it all and make suggestions for if we see something out of place. Knowing what you have is a great place to start. And like the others have suggested (which I'm sure you've been doing anyway) is using the search function and reading through the forum. Any one of the topics you've asked about has multiple topics covering it. But don't let that stop you from asking your specific questions.

I'm with Masscj7 and others that say have a plan...and then when you have one keep rethinking it. It pays to know where your headed so you don't do stuff twice or regret this or that decision. I'm not building a show jeep or anything but i knew what I was going to use the Jeep for most of the time and what I wanted to do with it. After that I laid out on a spreadsheet what I wanted work/upgrades I wanted and what I thought it would cost. I didn't follow it perfectly but it helped a lot.

Somewhere on here (at least I think it was this forum) someone has an excel spreadsheet that has all the "normal" stuff on it. It's pretty nice. I'll see if I can hunt it down. I have the raw file somewhere. Or if someone else knows where that post is.

 

[Masscj7]

Somewhere on here (at least I think it was this forum) someone has an excel spreadsheet that has all the "normal" stuff on it. It's pretty nice. I'll see if I can hunt it down. I have the raw file somewhere. Or if someone else knows where that post is.[/QUOTE]

UltraRunner has several excel spreadsheets I’m sure he’s share. He loves them.

Also, as Tech mentioned, almost every part or upgrade has multiple posts on the forum over the years. Search and read and then ask your questions and it may help you alleviate some of your noob feelings as you’ll be better able to articulate your questions.


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[mtnbiker4evr13]

For what you're wanting to do cruising around dirt roads the axles should be fine if the axle nuts are kept tight on the rear hubs. When those loosen up the hub can wear/stretch and slip on the axle shaft. For piece of mind, when you go to do the rear wheel bearings the 1 piece shafts are a cheap/easy upgrade on the AMC20.

The Dana 30 front end will be fine with 35s out of the rocks, the weak link will likely be the lockout hub or U-Joint if its bounced under power. Again, cruising dirt roads is very different than hardcore offroad trails. Keep in mind the tires are likely as old as the fuel lines so replacing them would be a good idea anyway for back country exploring, 33s are easier to turn so you could downsize while replacing.

The AMC engine if in good shape is a reliable setup with a close eye on oiling. Best to go through things and replace rubber lines, plugs, wires, distributor cap/rotor, filters, go through the brakes/wheel bearings, steering joints and the other baseline work for an old vehicle. Engine swaps while tempting can be problematic if you need a part in the middle of nowhere if a special adapter this/that part was used.

Definitely take pictures, there is a wealth of knowledge here that can help identify oddities.

 

[RiverandSand]

If you are still curious about the SBC swap this site Novak Conversions has a ton of info and they also sell parts to do the swap. As said above a swap isn't cheap, this site will give you an idea of those costs.
Remember we love pics, so post some up.

 

[JR74CJ5]

Lots of great advice so far - couple more points:

For 35" tires, you probably have a lift - post photos of the lift so we can see how it's done - I've seen some scary stuff sold by PO's that new jeepers don't understand the issues on. Post photos of the steering links too - the angles.

My best advice is to start tackling one research project at a time without doing any work on the jeep yet (besides the most basic upkeep). Reasoning, you might decide that the lift is garbage, remove scary blocks or something, then decide on 33" tires since the lift is gone and you just want a trail cruiser, and not need to beef the AMC20 hard, or buy 2 new 35's for the rotten ones, or... see my point? If you are going to want to swap a 350 in, then no reason to replace the current motor mounts or engine mount bushing, you'll need new ones for the new engine and trans...

What helped me was made a list of things wanted to check out, took photos of what I had, did some google searching first just to get my mind in the basic understanding area of the topic, then posted a thread about that topic here to get advice if still needed. Then I prioritized the lists, coordinated future plans into things I did (as much as possible) and got moving.

I have a 360. Lot of engine for a jeep. I'm young and like my "more power V8 Vrooom Vroom loud mufflers" phase still, but getting a bit further along, and tired of running out of gas lol. I've been contemplating a newer with fuel injection, smaller engine - probably mate up with my Chevy SM420 direct... I just paid out the booty for that 360 build within the last 3 years... Should have taken my own advice, but some things you just won't know until you get it on the road. So no major choices until you have it safe and spend a bit of time with her...

Cheers