1992 10 bolt gmc truck axle under my t bucket build?
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fletcherson
Well-Known Member
If it isn't what you want as far a gear ratio, I would hold out for the right one. You will have a bunch of time, etc in making it work in your car and updating it will be evasive if done later. Most guys want a 3.42 or taller, not that it will be a load, just do the math considering your desired cam, tire size, rpm, etc. do it once and make it what you want. Jmo.
cooter
Well-Known Member
I see a lot of s-10 axle or 9" ford or 8" ford or dana 60 or jag rear axles. Im kinda on budget. Some say this axle too wide? Im tempted to hit pul a part in mornin. Look for axle with 3.73 in a 8" or 9" ford. I can buy entire axle cheaper than i can regear this truck axle. Im talkin out loud here.
fletcherson
Well-Known Member
If being a posi isn't an issue to you, it should be fairly easy to find if your local yard isn't scrap happy. Being on a budget is another reason to not use parts you don't really want, they are budget killers when redoing stuff. Experience talking here, lol. I see a lot of s10 type rear ends in them and they are known to sport 3.42 and 3.73 gears. The 4wd ones are wider, but usually posi, so pay attention. Ford Rangers had decent difs too, depending on the year. Look for a 4 cylinder standard to get the taller gears. The ford 9 stuff as I have in mine is great, but usually not real cheap because it's in demand, but you never know till you look. There are lots of stuff available for them and they are very strong. Pay attention to the pumpkin offset as well as the width, some are less doner friendly than others. The f bodies have decent rearends for light cars, they have tall gears and posi traction and disc brakes are common in them. I don't know of anyone who used one in a t bucket, but I bet there are some.
baddawgcustoms
Active Member
Also it would be according to the rear style of your build. If it's bobtail with axle tucked close to the body, or even a short truck bed, the width in my opinion is perfect. I have a 54" s10 with only 3 1/2" backspace rims and the tires are really close to my body. Also think about the 700 trans has nice low 1st gear and can offset the high gear rear but you have to consider cam/performance you are looking for. If you will be taking long cruises the mileage would be awesome!! Put a lot of cam in it and it would be dreadful on take off. I got my rear out of a 2003 s10 with 32,000 miles on it at the scrap heap for $125 and the brake shoes still look new and has 342's. You are probably better off with a lower gear rear, because nobody leaves these cars stock......,,for long!!! 
My thoughts, sell that rear end. Craigs list for $150.00. With a 700r4 you need at least a 3.73 and maybe a 4.10. S10 rears are plentiful and cheap. You mentioned pull a part, I think you can get the s-10 for about $100 when you pull it yourself. Google s-10 rear end codes. These codes tell you what ratio and whether it is a posi or not. The codes are then found on the glove box door of the donor truck.
That rear end you have will be way too wide for what you need.
That rear end you have will be way too wide for what you need.
benT
Active Member
I've posted this info before, but its probably time to roll it out again. The S10 10bolt 7.5/7.625" rear end is a good choice for the light low to medium horsepower small block cars. If you're running a blower, turbo, nitrous, etc you will probably want to step up to a larger rear like a 9" or 12 bolt. Its pretty easy to find a good one if you are in an area with a few junkyards.
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 back- not a good look in my opinion. We used the same on our '23 project as it is running a wider front axle and the rear tires are not overly wide. You want to make sure the track width on the back is at least as wide as the front. With a 48" wide front axle, you should be ok with an 54.5" S10 rear on a '23 with wider tires.
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 if you do do not have an overdrive tranny and do any highway driving and 3.73's if you do have an overdrive trans.
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.
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 back- not a good look in my opinion. We used the same on our '23 project as it is running a wider front axle and the rear tires are not overly wide. You want to make sure the track width on the back is at least as wide as the front. With a 48" wide front axle, you should be ok with an 54.5" S10 rear on a '23 with wider tires.
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 if you do do not have an overdrive tranny and do any highway driving and 3.73's if you do have an overdrive trans.
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.
I agree with RPM. I have a 700R4 with 4.11 gears and I wouldn't be afraid to go to 4.56 gears. It all depends on what you want and how you drive. I have no problem with 2500 rpm @ 65 mph, some guys would rather have half that engine speed for the same mph. Besides, if you're cruising at 1400 rpm that 70,000 horse power naturally aspirated SBC you have is probably producing an honest 60. I would rather keep the R's up and have a little more poop when I jump on it.
fletcherson
Well-Known Member
The thing many forget to consider is the rear tire diameter. A 4.10 with a 700 r4 sounds extreme, but not with a tall tire. I am only adding this for those who may not have experience to draw from. Again, it's important to figure all the variables for the intended result before shopping for parts so you don't have to double back later. Figure the cam, converter, transmission, rear end gear, tire size, etc... to get the optimum rpm to match the driving style. Then go find those parts. There are many calculators available from gear and converter manufacturers, etc... to help with this chore, just do some on line searching before junk yard searching, it will be time well invested.
fletcherson
Well-Known Member
You can't argue with that, it cost that much to spend similar time eating out with a guest, and you don't have to get cleaned up or mind your manners, lol. That should be a good choice for a cruiser with gusto.
fletcherson
Well-Known Member
From experience, you have to be the early bird to find the 8, 9" stuff. Guys snatch em up pretty quick around here. You done well with that one. I had a 84 s10 blazer that I put a fairly stout 283 in and it was plenty strong.
fletcherson
Well-Known Member
More good stuff! The ratios for each gear in different models are usually published in quality service manuals, if you want to compare the lower gears for whatever you are computing. Also keep in mind the flywheel diameter, it makes a difference, especially when launching.
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