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Discussion Starter · #1 ·
I have a 1999 GMC Sonoma SLS extended cab with the ZQ8 package. And the rear end is shot. I don't know if from an accident or any other type of maliciousness as I have just acquired the truck a little over a year ago from my father. And he never wrecked it that I know of but just recently I did find out he had a new passenger side axle put in and "differential kit" put in, and since I've had it I had it in the shop as well to replace the same axle. Anyways moving on I have no money to put this truck in the shop anymore but I still need the truck and it's not running down the road too well. So I just the same year S10 short cab from a friend of mine for 100$(pretty much my budget for this endeavor!lol) but it's just body and frame and rear end and drive shaft now my question is can I put that 4 cylinder short cab rear end in my truck? I've never done a rear end before. I do know the pinion flanges are different. I'm just asking basically if it will work. And maybe how to go about doing it. Like I said I don't have anymore real monies to dump into it but I need the truck on the road ASAP, getting rid of it is not an option. And I'm my mechanic. I've just never done a rear end that's all, I'm a paint shop guy, but I think I can handle this if it's possible? I've turned every nut and bolt on my previous s-10 as well except for the rear end. And almost to that point with this one. Any help will be very much appreciated.
Thanks,
HazMat
 

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First thing you need to do is check out the SPID sticker in both glove boxes to fihd out what gear ratio they both are. If they are not the same it will make some changes in the way the truck behaves. Look at the "G" RPO codes. Usually S10's are one of four codes: GU4 - 3.08, GU6 - 3.42, GT4 -3.73, or GT5 - 4.10. If the 4 cylinder trucks ratio is numerically higher than what you have now it will accelerate quicker and use more gas. Unless it's the same ratio as you currently have your speedometer will be off and more than likely your ABS light will be on. You'll need to swap the pinion flanges. I'm sure you can find a You tube how to do it correctly. Put a new pinion seal in while doing it. Do not over tighten the one you're keeping. You can change the pinion depth and ruin the axle if you crush the crush spacer farther than it was. Other wise it's a matter of unbolting one and bolting the other in. I'd recommend new u-bolts, but sounds like another $50 is out of the question. When you separate the brake line from the axle plug it with a golf tee or something. If that big long line all the way to the front drains completely you'll be bleeding for days to get all the air back out and using a lot of expensive brake fluid.
 

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Discussion Starter · #3 ·
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First thing you need to do is check out the SPID sticker in both glove boxes to fihd out what gear ratio they both are. If they are not the same it will make some changes in the way the truck behaves. Look at the "G" RPO codes. Usually S10's are one of four codes: GU4 - 3.08, GU6 - 3.42, GT4 -3.73, or GT5 - 4.10. If the 4 cylinder trucks ratio is numerically higher than what you have now it will accelerate quicker and use more gas. Unless it's the same ratio as you currently have your speedometer will be off and more than likely your ABS light will be on. You'll need to swap the pinion flanges. I'm sure you can find a You tube how to do it correctly. Put a new pinion seal in while doing it. Do not over tighten the one you're keeping. You can change the pinion depth and ruin the axle if you crush the crush spacer farther than it was. Other wise it's a matter of unbolting one and bolting the other in. I'd recommend new u-bolts, but sounds like another $50 is out of the question. When you separate the brake line from the axle plug it with a golf tee or something. If that big long line all the way to the front drains completely you'll be bleeding for days to get all the air back out and using a lot of expensive brake fluid.
 

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Discussion Starter · #4 ·
Thanks for the info oldeerslayer. I think I might have uploaded the right thing here this is the truck that I just bought and it looks like I might have got lucky because there's hardly any rust on it and all that stuff looks kind of new for being a 2000. I mean the u-bolts right there are like brand new compared to the ones on my truck my GMC that is. Yeah I seen I guess their pinions are the same size ? just the swap the flange out and put it in there? And what do you think about cutting the bracket off of my rear end on the passenger side that attaches that third shock forward, and welding it on this one? What about my sway arm in the back I would have to weld the two little tabs on there to keep the brackets from moving around on this new rear end right? I'm just wondering I mean I'm not going to be trying to set any records or make any hard launches at Northeast Dragway of anything I just need transportation that's going to be you know reliable and other than this rear end issue, its all pretty new parts under mine, I mean I put moog tie rods recently I've done moog upper control arms with ball joints in them I've done steering gearbox moog Pittman and idler arm, moog centerlink/draglink. New shocks up front, and was about ready to start body and paint work and I got laid off my job and I had run slP out of GMC Sonoma funds if you know what I mean. I got cab corners and all kinds of stuff. And like I said it was my father's truck so getting rid of it's just not going to happen and when I do get the money I'm thinking about rebuilding that rear end of mine but if not then you know at least I'll still have the truck and be able to drive it I'm not worried about any gas really, as far as different gear ratios I guess goes, because I don't drive it crazy anyways it always got pretty decent mileage anyways I think compared to other vehicles ive owned. And I'd say it gets considerably better mileage than the 82 S10 I had with the 2.8 V6! Damn I miss that truck! had a lot of plans for that truck but I'm going to do to my GMC now what I was going to do to that hopefully... eventually, and if not my GMC at least I'll still have it and I've got this nice same color S-10 back here now I can maybe tub out a little bit!. But for now I just need to get back and forth with it and right here in town, not going to be traveling in it or anything like that. But I got the bed off and going to put it on mine, tomorrow I'll be tearing mine down. (my family did thanksgiving already) so I've got 4 more days and hoping it will be on the road before then. Anyways I'll let you know how it goes and feel free to guide me anyway you want man like I said never done a rear end before and and don't really have any help out here so.... Thanks again
 

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You got lucky on that rear end. Looks like new springs and brakes. I would not recommend using the springs. That part number is for heavy duty springs which would raise the rear of your ZQ8 and make it's ride harsh. You can leave your shocks connected to the lower pads when doing the swap. They don't need to come off. Looks like you have good u-bolts on the parts truck. As far as that pinion flange goes, be careful. You might be tempted to use the pinion flange that's on the rear end now. Since your extended cab has a different flange swap them or you'll have issues with your 2 piece driveshafts center joints location.
As far as that hop shock goes. If you're looking to use your truck as basic transportation, remove the piece from the rear end carefully with a cutoff, unbolt the rest. Clean and sell the kit. They're getting hard to find. This guy sold 2 sets in the last couple months on ebay for $175 each + shipping.
 

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Discussion Starter · #6 ·
You got lucky on that rear end. Looks like new springs and brakes. I would not recommend using the springs. That part number is for heavy duty springs which would raise the rear of your ZQ8 and make it's ride harsh. You can leave your shocks connected to the lower pads when doing the swap. They don't need to come off. Looks like you have good u-bolts on the parts truck. As far as that pinion flange goes, be careful. You might be tempted to use the pinion flange that's on the rear end now. Since your extended cab has a different flange swap them or you'll have issues with your 2 piece driveshafts center joints location.
As far as that hop shock goes. If you're looking to use your truck as basic transportation, remove the piece from the rear end carefully with a cutoff, unbolt the rest. Clean and sell the kit. They're getting hard to find. This guy sold 2 sets in the last couple months on ebay for $175 each + shipping.
Attached is a picture of the RPO in my glove box (the truck I'm fixing for basic transportation yes)
I am removing the donor rear end with the leaf springs still attached. I probably won't try and R&I the hop shock just yet, as I need to have the truck on the road ASAP. Will those springs adjust the height of the rear, or just affect the ride itself? There has been and likely will be again times where I need to haul loads in the bed. Nothing too heavy but definitely a few hundred lbs I'd say. I knew I'd have to switch out the pinion flanges, what does that involve? I've read in the Haynes book something about counting the threads and marking it and everything else but that's if you're putting the same one back on. And I'll put a new seal on there but I'm just wondering how to go about actually putting my flange on that rear end? Do I count the threads on my rear end and then match them to the new rear end maybe? I really appreciate all the info! I should've got on here years ago. I've always had an S-10, this is my first Sonoma, and my first extended cab.
 

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Discussion Starter · #7 ·
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Attached is a picture of the RPO in my glove box (the truck I'm fixing for basic transportation yes)
I am removing the donor rear end with the leaf springs still attached. I probably won't try and R&I the hop shock just yet, as I need to have the truck on the road ASAP. Will those springs adjust the height of the rear, or just affect the ride itself? There has been and likely will be again times where I need to haul loads in the bed. Nothing too heavy but definitely a few hundred lbs I'd say. I knew I'd have to switch out the pinion flanges, what does that involve? I've read in the Haynes book something about counting the threads and marking it and everything else but that's if you're putting the same one back on. And I'll put a new seal on there but I'm just wondering how to go about actually putting my flange on that rear end? Do I count the threads on my rear end and then match them to the new rear end maybe? I really appreciate all the info! I should've got on here years ago. I've always had an S-10, this is my first Sonoma, and my first extended cab.
 

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Discussion Starter · #8 ·
Also, sorry, I was wondering about pinion angle? Does leaving the springs on mean I don't need to worry about the angle? And if I take the springs off how would I put the rear end end I mine at the correct angle? Or how do I go about finding the correct pinion angle? Am I over complicating this? I apologize I just have never done a rear end swap before, and just would like it (need it) to be right the very first time. Thanks again
 

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Leave your springs in. Those springs will make your truck look like it's 1980 and you're going for that driving downhill look. The pinion angle is already set on the rear end by the position of the spring perches. You shouldn't need to worry about it or change it. AFAIK all S-series rear ends are set up the same.
For the pinon flange. Id use an impact to unscrew both of them. Once the nut is off they may need a little encouragement to slide off. Reinstall them with a 1/2 breaker bar and tighten until good and tight. Don't use a cheater pipe or an impact. That's when you'll over squeeze the crush spacer. Kinda like crushing a pop can. Once it's been done it won't go any farther w/o excessive force, if it was done right the first time. Which we can assume is so since the replacement rear end was working fine.
 
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