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What Rear End

trailshredder

trailshredder

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Is there a way to tell what rear end is in a truck other than the VIN? I know the rear end has been swapped out but don't know what to.
 
Look for a little aluminum tag attached to one of the bolts on the diff cover. It should show the gear ratio and the make of the rear end. ;)
 
If you're just looking for gear ratio, jack up the back tires, turn one by hand one full rotation and count the driveline revolutions. If you only jack one tire you have to double, or half, your counting....can't remember which way now, but with one tire on the ground you are working the spider gears which changes how fast the driveline turns.

Just thought of something. The gear ratio better be the original unless they also changed the front diff as well.
 
trouttrooper said:
If you're just looking for gear ratio, jack up the back tires, turn one by hand one full rotation and count the driveline revolutions. If you only jack one tire you have to double, or half, your counting....can't remember which way now, but with one tire on the ground you are working the spider gears which changes how fast the driveline turns.

Just thought of something. The gear ratio better be the original unless they also changed the front diff as well.
Click to expand...

Since it was done 40,000 miles ago, can I assume he changed the front dif as well? This is on a 1500 suburban, Do these front difs have the pump rub issue like the ones on the allison's?
 
If you have not noticed any drive-line binding, then your probably OK! If they changed out the read end, then they probably used the same gear ratio that was in the OEM differential. If not, then you would definitely notice within a few miles. Front end and rear end turning at different ratios.

The pump rub issues are with the transfer case, not the Allison! If it is a GM rear end, count the number of bolts. GM uses 10 bolt, 14 bolt, etc. I would venture to guess that the same type of rear end was put back into the Suburban. That would have been the easiest fix.
 
the number f bolts in the diff cover and if you have a hub section stuck out of the rear hubs(like the front) will tell alot of info. and turning the tire to figure out what the ratio is defiantly the easiest way.
 
RI Chevy Silveradoman said:
If you have not noticed any drive-line binding, then your probably OK! If they changed out the read end, then they probably used the same gear ratio that was in the OEM differential. If not, then you would definitely notice within a few miles. Front end and rear end turning at different ratios.

The pump rub issues are with the transfer case, not the Allison! If it is a GM rear end, count the number of bolts. GM uses 10 bolt, 14 bolt, etc. I would venture to guess that the same type of rear end was put back into the Suburban. That would have been the easiest fix.
Click to expand...

The guy said he put a 410 rear in it to pull his camper. I think it had a 373 in prior to that.
 
you can never assume anything. There are really stupid people out there.

Yes, with both back tires off the ground, tranny in neutral, turn one tire one full rotation, the driveline will turn 4 times plus a little more. That equals 4.10 gearing. Not quite 4 times is 3.73

The only time you would notice the binding would be in 4wd. If the only time 4wd was used was on ice or slippery mud it might not be noticeable to someone who doesn't pay attention to those things. It would feel really squirrelly though.

I suppose you could jack all 4 tires off the ground, put it in 4hi, tranny in neutral, make a mark on the front tires, rotate one of the back tires one rotation and see if the marks on the front tires stop at the same place. There's going to be a little slop with drivelines and tcase gears but it should come out pretty close.

If the guts of the differentials have been messed with you probably can't rely on any stamps on the outside saying what ratio it is.
 
trouttrooper said:
you can never assume anything. There are really stupid people out there.

Yes, with both back tires off the ground, tranny in neutral, turn one tire one full rotation, the driveline will turn 4 times plus a little more. That equals 4.10 gearing. Not quite 4 times is 3.73

The only time you would notice the binding would be in 4wd. If the only time 4wd was used was on ice or slippery mud it might not be noticeable to someone who doesn't pay attention to those things. It would feel really squirrelly though.

I suppose you could jack all 4 tires off the ground, put it in 4hi, tranny in neutral, make a mark on the front tires, rotate one of the back tires one rotation and see if the marks on the front tires stop at the same place. There's going to be a little slop with drivelines and tcase gears but it should come out pretty close.

If the guts of the differentials have been messed with you probably can't rely on any stamps on the outside saying what ratio it is.
Click to expand...

It is 4wd. I had it in and out of 4wd a few times on a hard packed gravel road and it went in and out and rode smooth. I may have misunderstood him that he said he put the 4.10's in. Maybe he ordered it that way from the stealer?!? Seems like a lot of work for a backyard mechanic.

I will check out the rotation sync on the front and rear tires. That is a great idea!
 
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Have the VIN checked out. It sounds like either a factory deal, or they installed diffs front and rear.
 
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