4x4 - Different gears front & rear? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cap'n Hook · 03-30-2010, 08:56 PM

So I've only used the 4 wheel drive once on my Jimmy in the year and a half I've owned it, but now I think it has different gears in the front and rear diffs.

I locked in the hubs and shifted to 4Lo, and drove down a mile of dirt road to my house. After about 500 feet, I noticed something didn't sound right, sounded like binding or something. So I let my wife drive a bit while I walked by the truck, and noticed both rear wheels would turn less than a quarter turn, then slide forward a bit, like they were locking up, then turn a quarter again, then lock.

The only thing I can figure is someone swapped out the rear gears and didn't change out the front with the same ratio. If the front was a 3.08 in theory, and the rear a 3.42, that may cause this? Maybe? I'm stumped!

The first time I used the 4 wheel drive I was on grass and leaves, and didn't notice this!

AJs72K5 · 03-30-2010, 10:30 PM

Certainly sounds suspect. If that is the case, be glad you did it in the dirt and not on the pavement as you would have been binding up REALLY bad. You have two options that I can think of at the moment....

Get the whole truck up on jack stands (one on each corner). Put the truck in 4wd and let it idle in gear. Check if front and rear are turning equally. OR...open up both pumpkins and check the gears themselves.

Burt4x4 · 03-31-2010, 10:13 AM

Ya, count the teeth on the R&P front and rear. If it's not that then your transfer case may have an issue, assuming the issue goes away when you move to 2x4?

67chevy2wd · 03-31-2010, 10:21 AM

Another thing you could do is put it up on jack stands. Put the transfer case in neutral and spin a tire and count the revs of the tire v.s. the revs of pinion. You might have to leave one tire on each axle on the ground though if the opposite tire turns while you are trying to turn the other.

SeventyOne · 03-31-2010, 03:12 PM

Quote:

Originally Posted by 67chevy2wd

Another thing you could do is put it up on jack stands. Put the transfer case in neutral and spin a tire and count the revs of the tire v.s. the revs of pinion. You might have to leave one tire on each axle on the ground though if the opposite tire turns while you are trying to turn the other.

This is the easiest way to figure out the ratio w/o pulling the inspection cover on the axles.

One tire revolution will equal some number below...
A little over 3 pinion revolutions = 3.08
A little less than 3.5 pinion revolutions = 3.42
You get the point

Just get some chalk for a maker and go to town!

03-30-2010, 08:56 PM	#1
Cap'n Hook Workin to live... Join Date: Jun 2003 Location: Texas Hill Country Posts: 261	4x4 - Different gears front & rear? So I've only used the 4 wheel drive once on my Jimmy in the year and a half I've owned it, but now I think it has different gears in the front and rear diffs. I locked in the hubs and shifted to 4Lo, and drove down a mile of dirt road to my house. After about 500 feet, I noticed something didn't sound right, sounded like binding or something. So I let my wife drive a bit while I walked by the truck, and noticed both rear wheels would turn less than a quarter turn, then slide forward a bit, like they were locking up, then turn a quarter again, then lock. The only thing I can figure is someone swapped out the rear gears and didn't change out the front with the same ratio. If the front was a 3.08 in theory, and the rear a 3.42, that may cause this? Maybe? I'm stumped! The first time I used the 4 wheel drive I was on grass and leaves, and didn't notice this! __________________ Jason

03-30-2010, 10:30 PM	#2
AJs72K5 Registered User Join Date: Nov 2007 Location: South Tx Posts: 1,083	Re: 4x4 - Different gears front & rear? Certainly sounds suspect. If that is the case, be glad you did it in the dirt and not on the pavement as you would have been binding up REALLY bad. You have two options that I can think of at the moment.... Get the whole truck up on jack stands (one on each corner). Put the truck in 4wd and let it idle in gear. Check if front and rear are turning equally. OR...open up both pumpkins and check the gears themselves. __________________ - AJ Gray Matter Build - 1972 K5 with some stuff

03-31-2010, 10:13 AM	#3
Burt4x4 Registered User Join Date: Feb 2000 Location: Modesto, CA Posts: 1,842	Re: 4x4 - Different gears front & rear? Ya, count the teeth on the R&P front and rear. If it's not that then your transfer case may have an issue, assuming the issue goes away when you move to 2x4? __________________ 1972 K5 MPFI454/Sm465/Np205/D60/14FFd/Re-Centerd H1s w/Swamper Iroks

03-31-2010, 10:21 AM	#4
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: 4x4 - Different gears front & rear? Another thing you could do is put it up on jack stands. Put the transfer case in neutral and spin a tire and count the revs of the tire v.s. the revs of pinion. You might have to leave one tire on each axle on the ground though if the opposite tire turns while you are trying to turn the other. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.