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Bought me a Used Jimmy and have a crazy 4 wheel issue.

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phrogs

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I purchased a Nice unmolested for the most part 90 GMC Jimmy. After I bought it last winter for a daily driver. I found a Issue with the 4 wheel drive durring a pretty good snow fall.
After Talking to the seller after that fun drive I was informed that the Rear gear was changed and the front was not!

So now I have the truck town down for some other work and I would like to address this issue.

what would you put in for gears for a daily truck that sees some towing and would use 4 wheel drive occasionaly?

recomendations is what im looking for, Im pretty sure the rear end was changed in an attempt to get better gas mileage im not convinced it worked.



Ok just yanked the covers

Rear I have 41-11 so 3.73
Front I have41-12 so 3.42

rear obviously has been open and has been leaking
front looked like it had never been touched. I do believe this ratio is on my window sticker.

My tires are 265/75/15 all around on the stock rims
 
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What gears do you currently have (front and back)? If stock height, 3.73's or 4.10's would be a nice fit. I have 3.73's with 35" tires and 6500 ft elevation. It definitely has to work to keep moving. I am in the process of switching to 4.10's which should help a little.
 
Well I have a 700R4 trans, Tire size im going to have to veryify and I need to crack open the Diffs and see what I have in there, I will be back with that info asap.
 
He's in Kzoo Michigan. Elevation about 800 feet. 3.73's max unless he's got 33's under it, maybe 4.10's then. Not a lot of hills around there.

3.73's are nice for stock 31-32" ish tires. Good combination of power while not spinning the engine fast for a daily driver.

Then again it could have 3.08's, 3.42's, or even 2.73's in the front.
 
Ah.....I remember the low elevations. Whenever I went to Seattle from Spokane or Wyoming, it was like driving a whole new truck! So much more power down there.

Just guessing, but if the front is different than rear, most likely someone had enough money to install a lower gear but not enough to change the front. So, this could be good news. If you have 3:73's in the rear, I'd leave it alone and then only deal with the front. Could be 3:42's.

My 89' came with 3:42's and I swapped them out early on (due to a rear end breakage) for some 3:73 axles.

Look in your glove box, GU6 is 3:42 gears. That could be your front ratio.
 
Ok just yanked the covers I wanted to be sure and I don't trust anything on a RPO tag on a used vehicle doesn't matter what it came with only what it has now so I pulled them off oil needed to be changed anyway.


Rear I have 41-11 so 3.73
Front I have 41-12 so 3.42

These are stock GM 10 bolts.
I also noticed that my front wheels do not spin together when I turn one or the other. Is this right? I can't remember if it is or not educate me..


The rear obviously has been open and has been leaking

front looked like it had never been touched dry as a bone. I do believe this ratio is on my window sticker but they are definatly different.


My tires are 265/75/15 all around on the stock rims


I must say that my location should not be used as a detrmining factor as I have to be ready to move all over the country due to work and will always call michigan home but it is very possible for me to end up in the hills, the swamp, the beach or even the desert.
 
Well I've still yet to figure out metric tire sizes lol, but I have 32s and 3.73 gears and 700r4 and it works just dandy for drivability. Even with my the junk 305 I had it never struggled that much. I want 4.10s at some point for the dunes however.

And welcome btw. I always like seein mi members!!
 
Yep, that's basically a metric 31x10.5R15.

I'd regear or find a 3.73 front 10 bolt.


I left Michigan under a crappy dark cloud but I still consider it home. As the location says, Hand State Expatriate.
 
x2. If you don't plan to go bigger than a 31" tire, 3.73s are what you want. Regear the front.

If 33s are in the future plans go with 4.10s front and back (obviously).
 
Another for the 3.73's for the towing and smaller tire size.

As for those talking about wanting 4.10's with their 35's, I'd go with 4.56's, I have 4.10 and 35" tires, it still lugs at highway speed and hunts in and out of overdrive.
 
4xcrazy said:
Another for the 3.73's for the towing and smaller tire size.

As for those talking about wanting 4.10's with their 35's, I'd go with 4.56's, I have 4.10 and 35" tires, it still lugs at highway speed and hunts in and out of overdrive.
Click to expand...

Same with mine. i lock it in third unless im cruising at 70.
 
I once bought a 71 K5 CST for 300 bucks,and soon found out why it was so cheap--someone swapped a 3.08 rear axle into it,and it had a 3.73 front axle ,so naturally it didn't want to move in 4wd,it twisted and groaned until one hub would release with a loud bang,so using 4wd was about impossible...

I did find and buy a 3.73 ratio rear end for it,but never did get around to installing it-I had two other GM 4x4s and a car,so I put off doing it,since I never drove the truck all that much,or far...

At the suggestion of a friend who used to do truck pulling,,I put larger tires up front (some 31x10.5's) and left the rears the stock 215/75-15's ,that made the gearing close enough to allow 4wd to be used without busting up the transfer case,etc.. it was a bit squirrely in the snow,and looked a bit goofy,but it worked!--better than being stuck with only 2wd.....maybe you could do the same to get by until you get the right axles that mtch installed..
 
Well I will be swaping out the front, but there are so many different gears. I want to be sure I'm getting the right parts. How do I know for sure?
I have a gm 10 bolt front axle but what am I shopping for, I see some gears advertised by axle like Dana 44 then some say they are 8 1/2 what do I need?
Thanks guys!
 
You need gears for a GM 10 bolt 8.5" front axle appropriate for your truck's year.

That simple.
 
You will also need a new bearing kit and seals....again for GM 10 bolt 8.5.

Be prepared though, once you have it torn that far apart, you should at least replace the axleshaft u-joints too (2 each).

If needed, upper and lower ball joints but that could be pushed off till later due to the amount of money going in at that point.

So:
New Ring and Pinion
Bearing Kit (with shims, I believe)
Axle seals
New axleshaft u-joints (Spicer for example....not Autozone brand)
 
Personally I'd just try and find a 10 bolt front axle with 3.73's. They aren't that uncommon. Dirt cheap too. Definitely less than paying to regear your existing front axle,
 
^^^^ A worthy option.

I did this many years ago when my rear end went out. I originally had 3.42 gears and the rear went out. The price to fix the interior parts vs. going the junkyard and picking up two Axles (front and rear) with 3.73's was cheaper overall.

The truck has well over 300k miles on it now. 200k with swapped out axles.

Furthermore, just a few weeks ago I picked up a whole rear axle for $98. You could do the same if you want to get a little dirty.
 
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