There is no cheaper rear to buy parts for than the 8.5 GM. They came in full size cars and trucks since the early 70's, F-bodies until 81, midsize cars until 77, vans, etc. They are everywhere.
The 8.8 is very popular, but didnt come out until 83, so they are not as plentiful.
Most aftermarket companies (Auburn, Eaton, Detroit/Tractech, Etc.) get similar money for parts between the two, but the 10 bolt will come up slightly cheaper with gears. Just look at the price of AAM gears.
There will obviously be exceptions from certain companies, but on the wholesale level which I worked at for many years the 10 bolt is cheapest. The strength edge goes to the 8.8 though. One more spline(although the spline diameter is actually the same, so really no difference there), larger pinion and carrier bearings, larger pinion and ring gear. The bearings are actually the exact same that are used in a 12 bolt and the ring gear diameters are almost identical.

 

Also something alot of guys don't realize the 8.8" Ford is NOTHING like a 9". Actually it is about the same as a GM rear 7.5"/8.5"/ AND the famous 8.875" or 12 bolt.

 

Ok I'll ask you. Would you rather be broken down than run anything ford?

Stuck in some kind of hillbilly time warp Ford vs Chevy... yeee hawww

 

Are you saying the 31 spline 8.8 has the same bearings as the 12 bolt?

Thats weird because the 28 spline 8.8 has the same bearings as the 8.5.


I think the reason the 8.8 is so popular (another reason) is the availabilty in a useable width.
What I see in junkyards...
The 8.5 GM's are mostly in trucks from the 80's and they're big. Not many cars with 8.5's laying around.
The 8.8's are in small trucks (4x4 or 4 liter), and mustangs (from mid 80's to todays models)which have widths more useable to bolt right in a lot of cars.

 

I held back, but I see you didn't.

Ben T.

 

Also, the "8.8" is rounded from eight and seven eighths (8.875")- the same exact size ring gear as the 12-bolt.

The 9" ford doesn't have a HUGE advantage just because of how it is designed. If that were the case the 8" ford (which looks nearly identical to nine inch) would be a strong rear and it is NOT.

Ben T.

 

NICE! First off I'm about as far from Hillbilly as you can get. Also I've fed myself and my family by turning wrenches for Chevy and I know that for most of the recent history GM was SOOOOOOO far tecnologicaly advanced in comperison than Ford it's ridiculous. Also yes the 9" is a bad *** rear but it also eats way more power (parasitic loss) than a 12 Bolt. Also 90% of the guys on this forum don't need a 9" the 8.8" is not at any true advantage over a GM 8.5" and at a loss compared to a 12 bolt. But the S60 (Dana 60) aside from mass is the best of them all it if I remember correctly even causes less parasitic loss compared to a 9".

And as far as your timewarp what is this whole site all about? We all talk about how we are faster than a Mustang or how a ZO6 is faster than a Ford GT. Hell if you go to the conversion/Hybrid section of this site there are guys putting LSx's into Mustangs. So what it really boils down to is most of the guys are stuck in the old hillbilly time warp of Ford vs. Chevy. Now I might take it a little farther by not being willing to hang a P.O.S. Ford rear in my little Blazer X or in My Monte. But you know what, odds are I won't be broken down on the side of the road 'cause I know how to build my ****.

 

Okay. I'll bite.

"Way more power"? Great way to keep myth perpetuated. Most swaps show a hp loss of less than 15 when swapping from a stock 10-bolt? Is this what you're considering eating "way more power"?

Here's something to chew on; put a set of 4.10:1 gears in a stock 10-bolt and go dyno. Guess what? Power will go down ~10hp at the wheels from the steeper gears. Most of the loss from swaping in a 9" could be attributed from the gear change.

So, I really wouldn't call 5hp a whole lot. It'd call it more like negligible. So, put down your corn cob crack pipe and get off the computer. Diddy needs help plowing the beans. Just joking with you. BTW, I used to think Ford sucked too back when I was in grammar school. Don't let the hick comments bother you. We're talking about camaro's here. Go ask any girl you want if a camaro is "cool".

Ben T.

 

It has to do with the position of the pinion gear in relation to the ring gear if you do a direct comparison their is more of a frictional loss compared to the design the GM style of rear uses (your beloved 8.8") included. Also like I said if you are really worried that you are making enough power to justify a 9" just get a S60 because it won't break. Oh and it's cheaper than a 12 bolt.

 

Hey I'm not worried about the Hilbilly barbs I'm a Fireman we have ALOT of down time and tend to pick on eachother all day long. Watch Rescue Me one day on FX it's only slightly exagerated.

Another thing if you look back a little bit in the thread you'll see I conceded that the Camaro is a different situation and also that I might take it further. But in all seriousness the Dana is a way better rear if you make serious Power and surprisingly it is reasonably priced in comparison to the 9"/12 bolt assemblies that are out there from Strange adn Moser. For my personal situation the 8.5" will be sufficient I'm only looking to get about 400hp to the street and it will be relativly cheap compared to the bolt in's from the big companies out there I priced it out w/o brakes and it was gonna be like $2500 I'll be able to build my 8.5" for over a grand LESS. Oh and there are a bunch of GN's running 9 sec 1/4 with a 8.5".

 

Who's the dumbass who decided to keep the 7.5 in the f-body for 20 years? Hell they went the distance to put a new 8.5 in a limited production 4.3 liter H.O. S series truck, only the ones with the five speeds.
Why didn't they ever put one in an f-body?

 

The 8.8 are the same for car and truck, the 12 bolt car bearings are the same as both as well as the 98-up 10 bolt truck rears. The 10 bolts from 97-earlier had different carrier bearings.

 

The 7 5/8" has a couple of advantages all be it none of them are strength.

1) less weight = better mpg
2) less frictional loss = better mpg
3) cheaper = cheaper
4) better mpg = less of an impact on the average of the line ups mpg


You can't agree with everything that someone does just because a person is a republican and they voted for Bush doesn't mean they agree with everything he does.


The S-10's got them in 5 speed apps only AND that was sporadic. The bean counters seem to run things more than the guys with common sense.

Also did you know that the OBD II system was developed by the General in the 90's and was so advanced at the time the Federal Government made GM sell the system to the other mfg's and made them run the system until they developed an equivalent.

 

i really like the idea of keaping everything on the car GM. im gonna call around and see what it would cost me to get a descent 8.5 from a late 90's GM truck and have it narrowed and an aftermarket ta put on it.
i plan on putting it in my road course car so it should be plenty strong and im sure much lighter than a 12bolt as well as a couple bucks cheaper.

does anyone know if the oem disc brakes will bolt up to these rearends?

 

I doubt it, but I'm not sure. I do know that your oem WHEELS will not bolt up.

After having built a few "custom" rears you really get what you pay for. I'd suggest a budget 9" Ford instead of the custom route.

Ben T.

 

Just have new small GM ends put on when you have it narrowed they have to put on new ends anyways they are like $90. You can have the axles redrilled and resplined but you would be better off just getting new axles they'll be stronger. I don't know what you gotta do for the T-arm though.

 

no, and neither will your wheels.

 

has anyone ever actually done it on a forth gen? becasue i am very curious to see what it costs.... and how the tourqe arm is on pics. would be great

 

Hey guys, I am new to the LSX world. I've been stuck in the V8S10 world for sometime. Having built and raced many V8S10's, I've gone through my share of 7.5's. For the S10 the 8.8 is a very good solution. Spending countless hours in junkyards measuring rearends, I believe the 4th gen rearend is like 65 5/8 inch from wheel mounting surfaces. If my memory serves me correct, a ZR1 4wd S10 is like 64 inches from wheel mounting surfaces. They all come with 8.5 10 bolts with 30 spline axles and I think 4.10 w/lockers.

So if you are any good with a welder, you should be able to cut of the bracket from the 7 5/8 and weld them on the 8.5. Correct me if I am wrong, but that would give you a rearend the is 3/4 of an inch narrower on each side. I know on my 2001 ws6 M6 with a 15x8 5.5 bs weld rim with 275/60/15, it rubs alittle on the rear fenderwell lip. So 3/4 of an inch would place the tire better inside the wheel well. 3/4 of an inch would'nt make all that much of a difference with the stock wheels mounted. And if it does, you could run some small spacers.

As for the torque arm, yes that would require some fabbing. I don't see that being too hard, because you have to fab mounting brackets for a four-link when laying frame on air bagged S10s. I've seen some of the brackets on the 8.8's, which are a good concept, but are questionable in strength. For example, if you built a clamp for the front of the rearend where the pinion bearing is. Then make your bracket for the torque arm to bolt to. Weld the torque arm bracket to the clamp you fabbed and then extend the back of the torque arm to the drivers axle tube. Kinda like how a ladderbar welds on around the axle tube, but as close as possible to the center section. Its hard to give you a picture, but the fabbed torque arm would look like an upside down "L". With the top part of the upside down "L" being the clamp around the front of the housing and the other end of the upside down "L" welded around the axle tube. The 90 degree part of the upside down "L" being where the torque arm bolts to. I hope this makes sense, because it is easier to explain on paper. In my opinion, being a welder and a fabber, not to much of a challenge to acheive.

Yes, I know a 9 inch is by far easier, but out here in Wisconsin I could get the rear end for like $250 complete, because they are to wide for the V8S10 guys to use. This is just a suggestion no punt intended. I am for going fast for cheap.