LocostUSA.com

Just thought I'd help clear up a few things about S10 donor parts (specifically brakes and rear ends.)

REAR ENDS

- GM made the 10 bolt in S/T-Series in a few different sizes - 7.5, 7.625, & 8.5. Identifying between these diffs is fairly easy work if you use the following tips: The 7.5" / 7.625" will have straight axle tubes, 8.5" should have a diameter change about 3" from the center section. Also, there are identification markers are on the bottom of the center section. The 7.5" and 7.625" will have two "fangs" that extend down from the housing, about 3/4" long and about 5" apart. They look like little triangles or cat's teeth (long slender & sharp). The 8.5" rear has casting lugs in the same location, but they're big rectangular blocks (like 3/4" or 1" across the face). Very easy to tell the difference. Check this link for a pic of the axles -


- The 4WD axle is about 4" (overall) wider than the 2WD axle, and the ZR2 axle is about another 4" wider than the 4WD axles (about 8" longer than the 2WD.) If a 2WD axle would require you to run 2" spacers, try the 4WD axle. Also, AFAIK, the ZR5 has the same axle width

- You could get the 8.5 (the strongest of the S/T axles) from a number of donor vehicles, namely, those with a V6 and MT (also, ZR2s only came with an 8.5.) However, this doesn't mean every V6/MT truck will have an 8.5. Use the tips above to verify which rear is in your donor.

- Each of these axles came in a variety of gear ratios. If your donor has the RPO code sheet (located in the glove box) intact, you can get the ratio from there. Look for one of the following codes:

GT4 3.73
GT5 4.10
GT7 3.33
GT8 4.10
GU1 2.41
GU2 2.73
GU4 3.08
GU5 3.23
GU6 3.42
G80 POSI-TRAC
H04 4.11

- You may have noticed POSI-TRAC listed above. Don't get too excited just yet, because GM used the Eaton Gov-Loc in all of it's S/T posi rear ends. While this is better than an open diff, it cannot measure up to the performance of some OE posi units or an aftermarket posi. The Gov-Loc requires about a 100 rpm difference in axle speeds to engage, so you basically have limited spin instead of limited slip. Then, once you get over 25mph or so and lift off the throttle, they unlock and won't relock until you slow back down below 25mph. Also, if you grenade a posi rear end, it will usually take the whole diff with it. So, consider your power level before paying extra for a posi'd diff.

BRAKES

- 97 and earlier S/T axles had drum brakes, while 98 and later had 11.5" disc brakes.

- Also, one of the great things about using GM parts is that SO much is interchangeable. For the S/T trucks you have the luxury of being able to use F-Body (Camaro/Firebird) and some Y-Body (Corvette) stuff when it comes to brakes. That said, a common upgrade for S/T trucks is to use the 98 and later F-Body rear discs (which bolt right up and only require modifying the parking brake cable) and upgrade the front discs.

- For the front discs, you can go with later model S/T brakes (IIRC, 98 and later have dual piston calipers and a 1" larger diameter rotor), F-Body brakes, or go aftermarket (CBR, Baer, etc... have kits.) Keep in mind that you may have to run 17" or larger wheels with some kits.

I'm sure there's more that will come to me later, but hopefully this will help some of you guys for now. A few links are below for those wanting more info:

http://www.cbrperformance.com
http://www.syty.net
http://www.s-series.org
http://www.baer.com

Wow,
Thanks so much for sharing this with the group! I'm going to sticky this.

WOW fantistic information! Thanks sytyguy!!

Another question for ya....

I'm planning on using S10/GM parts to build a immitation Super Stalker (L67 engine S10 front spindles and rearend) I will be racing with the car, and i will need a LSD rearend. Will a camaro LSD fit in those housings or would i be better off using a Camaro Rear end?

Thanks
Ken

Good Job sytyguy

You're quite welcome guys. I'm a Syclone/Typhoon (and general S-Series) guy by nature, so maybe I can bring some GM info with me over here.

To answer your question KENLUDE97, you can do an F-Body LSD swap into an S10 rear axle so long as you have 28 spline axles. 26 spline axles are limited to the Gov-Loc or aftermarket LSDs. However, keep in mind that (in the minds of most) the usable range of the GM 10 bolt (with substantial mods) stops around 400 HP, so if you have visions of more, you may want to consider a GM 12 bolt, Dana 60, Ford 9", or custom.

If you go with an F-Body rear, keep in mind that the 4th gen rears are 4" (overall) wider than 3rd gen rears (which already have a track width of 60.5"). But if you get a 4th gen rear, you'll almost certainly get a decent LSD (Torsen = good), rear discs, and a decent ratio (3.23 or 3.42 are most common). If you have an S10 rear and just want to put a decent posi in it, you could swap the Torsen unit from a late model F-Body (good time to swap in the rear discs) or get an aftermarket unit (Lockrite, etc...) Depending on the cost/availability of the F-Body unit (some yards will require you to buy the whole rear), you may come out cheaper by buying a new aftermarket posi. Plus, it may make you feel all warm and fuzzy inside to know that you have a practically NEW rear behind you versus an xxx,xxx mile posi from a Camaro that has been rode hard. Peace of mind can be very persuading.

The downside to the GM 10 bolt is the usable power level (when stock). I've seen 10 bolts come apart under V6 cars and 4 cylinder trucks, and while they're not the weakest rear you'll find, they aren't the strongest either. If you can live within it's power range (most of us over here are well within that range), then it can be a reliable and easy to maintain rear for you. Be aware that GM used the 10 bolt behind powerful LS1 cars because they figured the tires or clutch would slip, thus allowing the rear to live behind 300+ hp. If you plan to put a decent amount of power to a stock 10 bolt (225 rwhp is decent) and have good sticky tires and an LSD, don't be surprised if the diff doesn't like it.

The strongest 10 bolt that's somewhat readily available to get would definitely be the 8.5 available in some V6/MT S-Series trucks. However, they're getting more and more elusive to find. The best one to find easily, IMO, would be a '98 and later S-Series 7.625 with rear discs or a 4th gen F-Body with the Torsen LSD and rear discs (which one is better for you depends on what length axle you need.)

I'll study up on some F-Body intimates tomorrow (they're not my fortay), and hopefully, report back with some more concrete info.

Here's a link to Sam Buchanan's Torsen Posi install in an S10 that was originally open - http://home.hiwaay.net/~sbuc/stalkerv6/torsen.htm

Which one's lightest?

I'm clueless when it comes to 'murrican iron, but the nice folks at the wrecking yard next door said they had an S-10...it read "GMC" on the front and read "S-15" on the side but the wrecker told me theu're the same except for the labels. So I followed your clues and looked in the glovebox--Ta Dah! It claims the rear end is a G01. Anybody know what ratio that is?

Is it possible it was GQ1? From the GM RPO Code Wikki, I don't see a G01, but do see the GQ1, which lists it as a standard ratio, still not much help.

--JOsh

That's very likely. My eyes dqn't wqrk as well as they did in my yquth.

So can anyone tell me the "standard ratio"? It has an automatic trans, if that might have a different standard than a manual.

Most likely it is an open diff, and a gear set in the low 3's.

If you want strength, and are willing to look around a bit, the Ford Explorer 8.8 is much stronger than the S10 7.5 10 bolt, and if you look closely at the door edge and/or the diff tag (metal tag bolted on the diff pan) then you can locate a LSD with a 3.73 gearset.

The difference in length overall is 3 inches longer total over the S10 rear, and comes with 11" discs factory with the drum style emergency brake to boot.

Cheaper, easier, and a load stronger than the S-dime rears. I am dropping one in my S-10 (.5 inches wider at the spring perches than the 10 bolt). Common trick, and easily done.

I would use the 8.8 over the 10 bolt, or a 12 at this point (hard to find and expensive). The 9" is almost a no go at this point since most of the wrecking yard supply of rears has been exhausted for some time by the racers who bought them up. Dana rears are solid as stone, but very very heavy.

Doc

Most likely it is an open diff, and a gear set in the low 3's.

If you want strength, and are willing to look around a bit, the Ford Explorer 8.8 is much stronger than the S10 7.5 10 bolt, and if you look closely at the door edge and/or the diff tag (metal tag bolted on the diff pan) then you can locate a LSD with a 3.73 gearset.

The difference in length overall is 3 inches longer total over the S10 rear, and comes with 11" discs factory with the drum style emergency brake to boot.

Cheaper, easier, and a load stronger than the S-dime rears. I am dropping one in my S-10 (.5 inches wider at the spring perches than the 10 bolt). Common trick, and easily done.

I would use the 8.8 over the 10 bolt, or a 12 at this point (hard to find and expensive). The 9" is almost a no go at this point since most of the wrecking yard supply of rears has been exhausted for some time by the racers who bought them up. Dana rears are solid as stone, but very very heavy.

Doc

A couple things to keep in mind, these diffs. are heavy. The lighter models may not hold up as well to 400HP in the 3500 to 4500 lbs. cars they came out of, but an S10 based Locost like a Stalker is going to weight around 1450 lbs. Unless you're running wrinkle wall slicks at the drag strip, you are not going to be able to put all that power to the ground, and consequently you won't harm the differential. Secondly read all you can about Colin Chapman and the Lotus 7. He joked about building cars "then adding a lot of lightness", knowing full well lightness has to be engineered in from the begining. In the late '50s he was smoking V8 Corvettes with flat head 4cyl. Fords or Coventry Climax 4cyl., because some of those Lotus 7s were down to 990lbs. Take out weight and you need less power. Power to weight ratio is everything.

This is great info on the axles but the only thing I didn't see listed were the lengths on these axles. I am getting a 2wd S10 (4cyl) axle for free and I was betting that I would probably need a set of spacers for my 442 axles. Does anyone know the length of this axle (I would bet its the 7.5 or 7.625) thanks

My axle is from an 82? 2wd s-10 pickup with the 4cyl (GM 7.5). I finished stripping it and removed the existing spring perches and I'm getting ready to weld up tabs for the 4-link. I don't have the exact WMS to WMS measurement since I threw out the battered drums a while ago but I have some dimensions below. My approximate measurements make the completed axle around 52" which should fit nicely in a book frame. The yellow marks I made represent the placement of the mounting brackets for the 4-link. I have them marked with a felt tip but it didn't show up in the picture very well. I don't think this axle would work on anything wider than a book frame. (unless you find a different way to attach the trail arms, my frame mounts will be placed on tubes M1 / M2 per "book" spec) As you can see, there isn't much space to spare before you run into the backing plates.

anyone know the length of a newer axle 98-02?