Gears and axles

[slomo]

So I now have the funds to change the gearing and do some lockers. I have the Dana 30 up front and AMC20 in the back. Both gears are currently 3.31.

I want to go to 4.10 with the auburn ECTED electric lockers along with 1 piece axles in the back. Any recommended brands or kits for the axles? I have seen some from G2 etc.

Wished you lived near me. Would love to swap you for my 4.56 gears and full Detroit Lockers.

slomo

 

[slomo]

And you live in the desert. They would suck in in the snow and ice on the streets. A selectable locker is the best way to go. Jeep used them in the Rubi for a reason.

Amen to that. I have full Detroits front and rear. In the snow and ice, my CJ7 is scary on the street. That back end will come around before you know it. You are in trouble way before you can react. Gives you zero warning too. Would love an OX in the rear and keep the Detroit in the front.

slomo

 

[slomo]

Most of the folks I have talked said doing anything with an AMC20 is a waste and I should swap to Dana 44. I'm not doing any hardcore wheeling or crawling. At most an intermediate jeep trail.

Keep the 20. Install American made 1 piece axles. Not the cheaper Chinese junk. Gear and lock accordingly. Mine have been trouble free for nearly two decades.

In my opinion, you gain nothing with a 44. Other than cleaning out your wallet and in the case of the 60, dragging the ground at the pumpkin.

slomo

 

[slomo]

I am at the same point. Dana 30 front, AMC20 back, running 273:1 at the moment with 33" tires. my top speed at the moment is about 65 mph flat out. I dont wheel much, more of a disaster escape vehicle really, but would like to get more top speed and be able to go up a hill on a road trip faster then 40 mph.

I had decided on going to 373:1 r&p front and rear, detroit lsd in the rear and leaving the front open diff, and putting in the one piece axles in the rear.

For a mostly street, any reason to go to 410 or more?

258, 4 speed

Don't get caught up with all the low gears like I did. Remember your 4.2 is a LOW end Diesel like motor. You don't need all the rpms for mainly street duty. You'll wear out U joints faster, your engine and fuel mileage suffers. Plus you wallet lightens. First gear is useless on the street. Total waste of time. Some 3.31's or 3.50's might be do-able. Then hope you have an overdrive.

slomo

 

[slomo]

2.73's and 33" tires = slug. I think with 33's you need at least 3.54's

Remember 33" tires do not measure exactly that mounted. Mine measure 31.5" tall with a tape measure.

Calculated with a 2.73 gear and 31.5" tall tires is 1893rpm @ 65mph.

At 4.10 gear and the same tire you get 2843rpm at 65mph. Too much for a 4.2 on the highway.

My 4.56's are terrible on the street. Just get the jeep rolling SHIFT. Still walking speed SHIFT to second. At 35mph I shift to FOURTH in my T-4.

slomo

 

[Belizean]

slomo what tires do you have that are 33" but are really only 31.5" ? Getting real close to getting some new ones. Just curious.

 

[slomo]

slomo what tires do you have that are 33" but are really only 31.5" ? Getting real close to getting some new ones. Just curious.

Currently running Interco Thornbirds. Doesn't matter the brand. BFG's or insert brand name, none measure exactly what the sidewall says. Think mine were 31.5" new. Now they measure 31" tall. BFG 35's measure 33". Same BFG 33's measure 31's. Measure yours and see what you get.

slomo

 

[slomo]

Using a calculator like that is what led me to chose a 4.10 gear ratio. With a 33" tire on the ground and 28 p.s.i., for decent tire wear and a good ride, the rpms are a bit more to the point where for me is too much engine noise. As I recall, it was around 3200 rpm, which is what you should be getting per the calculator in 4th gear. I also have a calibrated speedo.

3200rpm in a 4.2 engine is pushing it. Way past the torque curve. All you get there is a huge nose dive on MPG, u-joint(s) wear, reduced top end cruising speed and many more. Talking about street driving here where 90% of Jeepers live.

slomo

 

[Posi]

Most offroad tires under 39.5" are smaller then stated, except Q's.
39.5" and up typically spot on.

 

[Belizean]

Currently running Interco Thornbirds. Doesn't matter the brand. BFG's or insert brand name, none measure exactly what the sidewall says. Think mine were 31.5" new. Now they measure 31" tall. BFG 35's measure 33". Same BFG 33's measure 31's. Measure yours and see what you get.

slomo

I measured my 30's which are close to slicks now with literally no tread and are close to 28 1/4 maybe. They are what is left of BFG M/S tires

 

[JAK]

I'm running 33's, 4:56 with a t-5 and 2700 rpm @ 70 mph which is way to fast anyway for the Jeep. I can cruise 60,65 mph right around 2200 rpm...fyi

 

[Lumpy Grits]

I'm running 33's, 4:56 with a t-5 and 2700 rpm @ 70 mph which is way to fast anyway for the Jeep. I can cruise 60,65 mph right around 2200 rpm...fyi

Why do you say 70 mph 'is way too fast anyway for a jeep' and 65 mph is OK?
My '7' will cruise all day at 70-75 mph without issue.
LG

 

[Belizean]

For an ole fossil like you 70 is no problem unless there are others out there, then there is plenty of problems for the rest of us

 

[Lumpy Grits]

When we are north of the city here, the freeway speed limit is 70mph.
If you are not going at least 75mph or faster, you'll get passed like you are sit'n in a park'n lot.
Gotta stay with the pack.
LG

 

[JAK]

Why do you say 70 mph 'is way too fast anyway for a jeep' and 65 mph is OK?
My '7' will cruise all day at 70-75 mph without issue.
LG

Lumpy, that was supposed to be a sarcastic comment, I have to remember its hard for people to pick up on that sort of thing though text. Our speed limits out here are 75 mph, so yes when cruising 70 I get passed like I'm standing still. But that's O.k. (I'm glad to see some of you had fun with this though.)

 

[Hedgehog]

My '75 has plenty of punch to go +75, But you don't want to travel that fast in it. The old gal will haul along fairly well @65 mph, @70 she's whispering in your ear .. "don't do anything drastic with that steering wheel." .. @75 she says, "you have little control over what I'm going to do now."

 

[mtnwhlr]

A 7 with wide-trac axles will do 75mph no problems but I wouldn't do it in a 5 with narrow-trac axles.

 

[Lumpy Grits]

A 7 with wide-trac axles will do 75mph no problems but I wouldn't do it in a 5 with narrow-trac axles.

Helps even more, when the frontend is well within the alignment specs too.
LG

 

[Belizean]

Yeah just make sure you're not riding on Firestone 500s at 70-75 or you could be cart wheeling

 

[JAK]

Helps even more, when the frontend is well within the alignment specs too.
LG

Alignment? I always thought my Jeep was pulling right because it wanted too get off the pavement and on the dirt. Maybe I'll look into this whole alignment thing.