4.10 or 4.56 or in between

[gw33gp]

My 89 STX with 2.9L engine and 5 spd manual had 3.73 gears when I bought it new. I switch quickly to 31" tires and did not like how it worked off road and towing. I used up the clutch in about 70K miles. I then installed 4.10 gears and was very happy with its off-road manners and towing became easier. The clutch lasted well over 100K miles with the lower gears too.

 

[BlackBII]

If you don't spend a lot of time at 70+mph, I would go 4.56.

 

[stegomon]

D35 and I have an 8.8 I can swap in. I have a few 4.0s laying around. Just need a trans. I think it would be cheaper to go with the 4.0.

 

[Lil-Pony]

Again DOUBLER with 4.10s

 

[AgPete139]

After screwing around on the calculator I found that tire size multiplied by .13 gives a ratio closer to what ppl prefer like 3.73 and 29s, 4.10 and 31s, 4.33 and 33s, 4.56 and 35s, 4.88 and 37...

This ratio is mostly for mixed performance, I feel. That and the TRS Tire & Gear Calculator are close.

On my 4.0 M5OD & 35's, since it's a DD, I would have preferred to go with probably a 4.56 instead. I find myself turning 70 mph @ 3,000 RPM. :-( Best mpg I've gotten is 17.5 mpg highway.

Back on topic, on my last truck with 4.0L 5R55E 4.10's on 33's, I was very happy.

Stego, if you are mixed driving, I'd probably hit the 4.10 on your 2.9.

 

[Surrey]

D35 and I have an 8.8 I can swap in. I have a few 4.0s laying around. Just need a trans. I think it would be cheaper to go with the 4.0.

Okay make sure you swap that 8.8 in, no point in buying gears for a 7.5".

a 4.0 swap would be a good option, but so would 4.10 or 4.56 gears. The difference from one to the next is only about 10%, so either should work, and it really just depends on whether you want the highway mileage of 4.10 or off-road low end of 4.56

 

[lil_Blue_Ford]

Maybe I just have an oddball 2.9L.....

My choptop has a 2.9L, FM-146 trans, 4.10 gears and I ran old bias-ply 33's on it. It went just fine (although those bias ply tires didn't seem to like speeds over 60 mph, I'd start to get a lot of vibration after that). I just put 35" radials on it, haven't really had a chance to test it out but it goes down to the end of the street just fine (had it up to 40 mph). Next week I should be able to test it out a little better. I think I lost a bit of my crawl though, but a 4.0 swap is planned for this fall.

I did do a good tune-up on the 2.9 and am running the larger throttle body, that seemed to have helped it's performance a bit.

 

[Surrey]

Maybe I just have an oddball 2.9L.....

My choptop has a 2.9L, FM-146 trans, 4.10 gears and I ran old bias-ply 33's on it. It went just fine (although those bias ply tires didn't seem to like speeds over 60 mph, I'd start to get a lot of vibration after that). I just put 35" radials on it, haven't really had a chance to test it out but it goes down to the end of the street just fine (had it up to 40 mph). Next week I should be able to test it out a little better. I think I lost a bit of my crawl though, but a 4.0 swap is planned for this fall.

I did do a good tune-up on the 2.9 and am running the larger throttle body, that seemed to have helped it's performance a bit.

As stated, my old truck had 3.45s and would do 120km/h down the highway on 31s. These engines CAN be good... Just not always, especially at this age.

 

[Mudstomper99]

Don't wanna start a new thread so figured I would ask in this one seems there are a few different opinions. I have a 95 with the 2.3 and 5spd trans. I just put on 33x12.50s and seem to have lost a to. Of power of the 32s it replaced. I have factory 4.10s and was thinking about swapping in a 8.8 and 4.56. Do you think it's worth it or should I go with 4.88s?

 

[4x4junkie]

Don't wanna start a new thread so figured I would ask in this one seems there are a few different opinions. I have a 95 with the 2.3 and 5spd trans. I just put on 33x12.50s and seem to have lost a to. Of power of the 32s it replaced. I have factory 4.10s and was thinking about swapping in a 8.8 and 4.56. Do you think it's worth it or should I go with 4.88s?

Definitely 4.88s for sure.


I'd also go 4.56 w/31s on a 2.9L in a heartbeat. Even my 5.13s w/35s I find a tad tall at times on the street. In spite of that, I still get low-20s MPG.

 

[Mudstomper99]

Good to know I was leaning that way just didn't know if the 4.88 would be to much

 

[lil_Blue_Ford]

As far as the OP goes, I can give an update on my choptop running the 35's and 4.10s. First through third it pulls pretty hard, fourth and OD it seems a little weak. It'll run along just fine on the level but on hills I lose speed in a hurry in 4th and OD. I haven't really tested it's ability to crawl, but it's probably not going to be the best.

I know my odometer is off by a lil bit, but not taking that in to account, my last fill up put me at just over 17 mpg city.