what year s-10 rear end is best to use
- Thread starter 76 harley
- Start date
76 harley
Member
how about 3.75 gear
benT
Active Member
I'm running the wider blazer rear end in my '27. The standard S10 is too narrow. The narrow ones work well with the '23 T's with beds, as long as you have wider back wheels and/or a standard width front axle. Some front axles are a bit wider than others and you could have a front track wider than the boack- not a good look in my opinion. With a 48" wide front axle, you should be ok with an 54.5" S10 rear on a '23.
With that being said, here is info I have compiled and written as this subject as it comes up often - I suggest you print it and take it with you to the junkyard so you can get one with a gearset you want. I'm partial to the 3.42's or the 3.73's if you do do not have an overdrive tranny and do any highway driving.
S10/Sonoma 7.5/7.625 Rear Axle Info
Chevrolet S10/ GMC Sonoma rear axles are a great choice for small lightweight Hot Rods such as a T-Buckets or early roadsters. These rear ends were made for many years and are plentiful and inexpensive to buy in junkyards all over. Nearly every part is available as a replacement from all of the standard auto parts retailers.
Finding a good rear end for your project:
GM made millions of S10's and they are perhaps the most found vehicle in junkyards today. Finding a good one is not too difficult providing you have a junkyard or two near you. Before heading out to the boneyard, I would first figure out what width of axle you need, and what gear set you need.
S10 2WD's have a drum to drum mounting width of 54.5" which is perfect for a T-Bucket with larger back wheels. The Blazer and 4WD models have about 4.5-5" more overall width and works well for 26 and newer fender-less roadsters, and 23 style T's with narrower rear wheels. Rear axle ratios can be found by looking at the sticker in the glove box that has the RPO codes on it. Try find an axle that has the ratio you want as it will be much cheaper and easier than buying one that needs a gear ratio swap. As for year of S10, I recommend finding one from the newer body style (1994 and newer) The newer brakes have a bolt-on wheel cylinder that is preferred over the earlier style that uses a ring retainer. Newer axles are usually in better shape and have less miles, so I'd always recommend finding one as new as you can. One last item to consider: There are a couple kinds of pinion yokes. You will want a standard yoke to accept the u-joint. A lot of these rearends had a yoke with a balancer. You can swap these out with the simpler style. While you're at it, get the matching driveshaft!
Widths:
S10 2WD: 54.5" Mounting Surface to Mounting Surface
S10 Blazer: 59.5" Mounting Surface to Mounting Surface
S10 4WD: 59.5" Mounting Surface to Mounting Surface
Bolt Pattern
5x120 (5x4.75")
Lug thread: M12x1.5 (12mm)
Axle Tube Diameter:
2-5/8"
Brakes
Rear Drum Brakes changed in 1992. Drums, cylinders and backing plates do not interchange with earlier models (83-91). The later brakes are preferable due to the bolt on wheel cylinders over the earlier style with retaining ring clip.
Drums: 9.5"x2"
Wheel Cylinders 3/4" (W/Power Brakes).
Disc Brakes: Some newer models came with rear disc brakes. These can usually be picked up for the same price, however replacement parts may be more costly.
Ring Pinion / Spline Size:
7.5" Ring Gear / 26 Spline Axles 1983-1992
7.625 Ring Gear / 28 Spline Axles 1988+
Rear Axle Codes (RPO - Found on tag in glove box)
GU2= 2:73 ratio
GU4= 3:08 ratio
GU5= 3:23 ratio
GU6= 3:42 ratio
GT4= 3:73 ratio
GT5= 4:10 ratio
GQ1= Open Differential Rear Axle
G80= Positraction/Locking Rear Axle (usually is next to the ratio code on tag)
Carrier Breaks: 2:73-3.08 ; 3.23-4.10 (3.08 and lower will not fit in 3.23 and higher and vice-versa). New pinion/ring gear sets can be bought to interchange.
Seals & Bearings
Wheel Seal: Timken 8660S (83-91) 4739 (92-02)
Pinion Seal: Timken 8610
Axle Bearings: Timken 5707
*This information has been complied from varies sources as well as the authors own experience. Information is believed accurate, but not guaranteed.
With that being said, here is info I have compiled and written as this subject as it comes up often - I suggest you print it and take it with you to the junkyard so you can get one with a gearset you want. I'm partial to the 3.42's or the 3.73's if you do do not have an overdrive tranny and do any highway driving.
S10/Sonoma 7.5/7.625 Rear Axle Info
Chevrolet S10/ GMC Sonoma rear axles are a great choice for small lightweight Hot Rods such as a T-Buckets or early roadsters. These rear ends were made for many years and are plentiful and inexpensive to buy in junkyards all over. Nearly every part is available as a replacement from all of the standard auto parts retailers.
Finding a good rear end for your project:
GM made millions of S10's and they are perhaps the most found vehicle in junkyards today. Finding a good one is not too difficult providing you have a junkyard or two near you. Before heading out to the boneyard, I would first figure out what width of axle you need, and what gear set you need.
S10 2WD's have a drum to drum mounting width of 54.5" which is perfect for a T-Bucket with larger back wheels. The Blazer and 4WD models have about 4.5-5" more overall width and works well for 26 and newer fender-less roadsters, and 23 style T's with narrower rear wheels. Rear axle ratios can be found by looking at the sticker in the glove box that has the RPO codes on it. Try find an axle that has the ratio you want as it will be much cheaper and easier than buying one that needs a gear ratio swap. As for year of S10, I recommend finding one from the newer body style (1994 and newer) The newer brakes have a bolt-on wheel cylinder that is preferred over the earlier style that uses a ring retainer. Newer axles are usually in better shape and have less miles, so I'd always recommend finding one as new as you can. One last item to consider: There are a couple kinds of pinion yokes. You will want a standard yoke to accept the u-joint. A lot of these rearends had a yoke with a balancer. You can swap these out with the simpler style. While you're at it, get the matching driveshaft!
Widths:
S10 2WD: 54.5" Mounting Surface to Mounting Surface
S10 Blazer: 59.5" Mounting Surface to Mounting Surface
S10 4WD: 59.5" Mounting Surface to Mounting Surface
Bolt Pattern
5x120 (5x4.75")
Lug thread: M12x1.5 (12mm)
Axle Tube Diameter:
2-5/8"
Brakes
Rear Drum Brakes changed in 1992. Drums, cylinders and backing plates do not interchange with earlier models (83-91). The later brakes are preferable due to the bolt on wheel cylinders over the earlier style with retaining ring clip.
Drums: 9.5"x2"
Wheel Cylinders 3/4" (W/Power Brakes).
Disc Brakes: Some newer models came with rear disc brakes. These can usually be picked up for the same price, however replacement parts may be more costly.
Ring Pinion / Spline Size:
7.5" Ring Gear / 26 Spline Axles 1983-1992
7.625 Ring Gear / 28 Spline Axles 1988+
Rear Axle Codes (RPO - Found on tag in glove box)
GU2= 2:73 ratio
GU4= 3:08 ratio
GU5= 3:23 ratio
GU6= 3:42 ratio
GT4= 3:73 ratio
GT5= 4:10 ratio
GQ1= Open Differential Rear Axle
G80= Positraction/Locking Rear Axle (usually is next to the ratio code on tag)
Carrier Breaks: 2:73-3.08 ; 3.23-4.10 (3.08 and lower will not fit in 3.23 and higher and vice-versa). New pinion/ring gear sets can be bought to interchange.
Seals & Bearings
Wheel Seal: Timken 8660S (83-91) 4739 (92-02)
Pinion Seal: Timken 8610
Axle Bearings: Timken 5707
*This information has been complied from varies sources as well as the authors own experience. Information is believed accurate, but not guaranteed.
EX JUNK
Moderator
What Ben has posted is EXCELLENT info on the S10 rears. My car is a '25 with a turtle deck rear so I have the 2WD version of the S10 rear. My front axle measures 48 1/8" center to center of the kingpins and my 155/80x15 front tires measure 58 3/8" center to center of the tread and 63 7/8" outside to outside on the tread. The rear tires are 285/70x15 and measure 55 7/8" center to center on the tread and 64 3/4" outside to outside on the tread. These measurements should give you some idea of positioning like Ben was referring to.
Jim
Jim
76 harley
Member
the one I got is out of 1987 s-10 with 3.73
Bowtie T
Active Member
Ben T & Ex Junk are right on the money. I went with a 2wd blazer unit. It is a little wide so I just bought my wheels with a deeper back space (6-7") to fill the space
between the tire & body. The easy way to pick the rear you want is to go to the u-pull it,write down the vin# from 4 or 5 prospects, call the parts department of
your Gm dealership, they can give you the gear ratio & tell you wether it is posi or not. A lot easier than crawling under & pulling the covers off!
between the tire & body. The easy way to pick the rear you want is to go to the u-pull it,write down the vin# from 4 or 5 prospects, call the parts department of
your Gm dealership, they can give you the gear ratio & tell you wether it is posi or not. A lot easier than crawling under & pulling the covers off!
benT
Active Member
Really -All you have to do on an S10, Blazer, Astro van, etc (before you pull it!) is open the glove box and look a the code on the RPO sticker. Use the codes that I posted in my previous post. Much easier and faster!
EX JUNK
Moderator
Thanks guys,but rear end was pulled and all I had to go on was what the seller was telling me.It turn out to be 87 blazer with the 3.73 gear
2WD or 4WD???
Jim
76 harley
Member
4wd
Allen27Tcoup
Member
I've used the ford explorer 8.8 rear from the 97 / 98 has stock posi and 3.73 gears and disc brakes all under a hundred dollars at the local pick and pull.
smokeyco75
Member
Mine is from a 96. 95 bucks. 3.42 gears
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