chevyowner02

iTrader: (3)

Has anyone done it yet or like me try? The length from backing plate to plate is 55'. The whole thing is 61' The factory 10 is 54' not sure of over all length.Now There is a local shop here that dose alot of fab work (racecars dragcars) I talked to him today he told me as long there is no cast pices on your rearend he could cut them off and weld them on mine. The car will have a LT1 with hotcam,headwork,bolton stuff by no means a 400hp machine.But I want a rearend that will hold up.

ttypecamaro

iTrader: (2)

the torque arm mount is cast into the stock rear... that seems to me the hardest part about converting the rear end.

Shagwell

The tq arm mount is cast into the factory housing. There's no cut and weld to it.

With that power level, a mildly modded factory 28 spline 7.5" 10-bolt will hold up fine.

chevyowner02

iTrader: (3)

Ok i guess I'm 50/50 with the small 10 bolt.Shagwell what do you mean by mildly modded? Like what to modd to make it hold up for a little while? THANKS

ttypecamaro

iTrader: (2)

for what I think is the best way to modify the stock 7.5" 10 bolt rear: Read the currently active thread called "Bulletproof 10 bolt? you be the judge".

https://www.thirdgen.org/forums/tran...f-10-bolt.html

Batass

So the torque arm is the problem? I've been wanting to do this too. There's no way to put one on there, or it just isnt cost efficient? I'm building a 600hp 383, with street tires, a 5-speed, and hardly any track use. I dont think a beefed up 7.5 is going to do it for me. The 8.5 seems perfect. Really dont want to spend another 2k on a rear!

ttypecamaro

iTrader: (2)

Its probably possible (while difficult) to weld up a bracket, but getting the pinion angle perfect will most likely require an adjustible torque arm (more money).

edit: And you can probably forget about rear disk brakes, unless you buy a conversion kit... then after all that work and money it would be cheaper to buy the moser rear.

Batass

Disc brakes, that was another concern......I'm wondering if it would be even worth it to beef up the stock one and use it until it breaks.....might break rather quickly with 600hp at the motor......?????Maybe just keep it stock 'till it blows. Then fork the money for a 12.

Shagwell

I'm running around 500+hp at the flywheel, and so far my 7.5 10 has yet to even complain about the 5200+ rpm clutch side-steps.

Good axles, solid pinion spacer, support cover(aluminum girdle) , and a decent gear have held several people on this board into the 10's.

A true 600hp na out of a 383? That'll take a serious combination. - Also, I hope you're not talking a T5 5-speed.......

Batass

Whoaaa, vortech supercharged, and a tko 600. Well, to build up the 10 bolt that way would probably cost about $1000 right? Depending on my money situation at the time, it might be worth the extra grand for peace of mind.........maybe not.....

chevyowner02

iTrader: (3)

Ok is there a a better year than others? If so witch one would be better? Not sure if I need or want a posi.

Sonix

iTrader: (1)

Yes, you do need and want a posi.

There are lots of threads on here about beefing up a .75" 10 bolt, I made 2 threads with a few pictures, and a lot of info on "how to", and which part#'s to buy, etc etc.

An 8.5" is what i'll be using in the long term future. Welding to cast iron isn't the end of the world, you just have to realize that it's not steel, and treat it differently. There are (were) 2 threads in quick succession, about a month ago, where two guys used 8.5" rears. Each had a different way to put on a torque arm mount. One was welded on, not quite finished I don't think. The other was a big AL block, clamped on.

The other brackets can be stolen from the 7.5", or made up (they aren't really complicated brackets). Welding those onto the tubes would be a breeze.

If you're doing a home made TA bracket, might as well make up your own TA to go with it, and make it adjustable. If you've got 600HP, I think it'd be worth your while.
The guy with shy of 400hp, might as well stick with a 7.5" 10 bolt, save the headaches.

ede

anyone with welding and fabrication skills could narrow a rear and relocate the brackets, and make any needed brackets. there isn't any reason you could weld to the casting with next to no extra precautions.

chevyowner02

iTrader: (3)

Ok would it be a good ideal to buy a stock rearend with posi or to go buy a aftermarket posi unit?

Sonix

iTrader: (1)

What kind of an answer are you looking for there?
Obviously an aftermarket posi is going to be better, but it's around $400. Is it worth it to you? Your call, no one else can really tell you what you want.

chevyowner02

iTrader: (3)

Well......lol I figured that but after looking at the price dang. Do you have the link(s) on what you did to your rearend? Thanks
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Well......lol I figured that but after looking at the price dang. Do you have the link(s) on what you did to your rearend? I did a search and seen a couple you had did but none with part #'s and things Thanks

Sonix

iTrader: (1)

here are the 3

https://www.thirdgen.org/forums/tran...t-rebuild.html

https://www.thirdgen.org/forums/tran...r-removal.html

https://www.thirdgen.org/forums/tran...e-removal.html

They were roughly at the same time. Guess I didn't document it well. Anyway, ratech 4111, and the zytanium cross shaft were the only ones that are "hard" to find. The girdle you can get anywhere, I used the summit one. I left the stock axles and posi and gears in there, so I didn't go all out on it.

Batass

Well I think I'm going to try the 8.5. Why not make the project bigger? It'll give me something to do while the motor is in the shop. Its too bad no one has any detailed guidelines on one. I dont know jack about rears. I can weld well but I'll let cast up to someone else. Thanks for some good answers.

chevyowner02

iTrader: (3)

Yea I think I'm going to try it also I dont want to spend $500-1000 on a rearend that will be a ticking time bomb!

ede

if you can weld steel you can weld the cast part of the rear. it's not iron and doesn't really require any extra precautions other then LH rods.

Sonix

iTrader: (1)

? The cast part of an 8.5" GM rear is NOT cast iron you say?
You sure about that Ede? I thought it was the same as the GM 7.5", and it was cast iron?? And you'd use a lot of pre-heating, etc, post heating, and use a high nickel rod...
LH rods - low hydrogen? Like E7018?

BMmonteSS

You guys would have a lot easier time fabing up a ford 9". It has a steel housing that is pretty easy to weld up a torque arm mount to. Also currie sells a bolt on mount that bolts to the center chunk bolts. I do believe they even sell the rest of the brackets you would need. The only downside to the 9" is you'll have to get your axles and drums/disk redrilled for the chevy bolt pattern. The benefits are that they are much more common and cheaper than the chevy 8.5, they have bolt in axles so you don't have to worry about your axle passing you up. You can get them in 31 spline from the factory and they were used in everything that ford built so finding one the right width should be pretty easy.

A bone stock 9" and ford trac-lok will take just about anything that street tires can dish out. If your thrifty like me you can have a 9" with disk brakes, posi, and 3.50 gears for less than $500.

Shagwell

-
Ede is correct, most diff housings are cast steel, not cast iron. Cast steel will weld much easier than cast iron, but it is still a bit trickier than regular plate steel.

As for availabilty, that's why I've been thinking more along the lines of an Ford 8.8 instead of the Gm 8.5 10-bolt. - I've broken a few 8.5 10-bolts..... For me it'll be aftermarket axles and a custom housing length to make it fit just the way I want, so I'm just gonna use 9" housing ends and buy axles machined for press on bearings, thus eliminating the possibility of an axle in the passing lane...by itself....

Any way you go about it with the intentions of building it strong, you're gonna spend some $. For what I want out ot the car, I'd rather have the lighter rear so I've been looking at 12-bolts, then this 8.8 idea came up while working on a buddies stang....

chevyowner02

iTrader: (3)

Ok I talket to the guy's at currie they do sell the part 149.99 Pn#CE-7009. I did have a 9' at one time to go under it at one time. But I did not like the Idea of having my wheels drilled for the lug pattern. Around here I can find them all day in the $50 and up range I dont know what it will/would cost to rebuild one? Mabey more or close to what a NEW 9' OR 12 Bolt would cost?

Sonix

iTrader: (1)

hmm, I ask because;
http://www.nastyz28.com/forum/showth...ing+axle+tubes

I've only heard that they are cast iron.

Can we agree the 7.5" 10 bolt is cast iron?

BMmonteSS

No need to redrill your wheels for the ford bolt pattern, just have the axles redrilled for the chevy pattern along with whatever brake rotor/drum your going to use. I used the early camaro rear disks with stock GM calipers along with a cheap set of weld on caliper brackets you can get from any circle track vendor.

As for rebuilding, I don't think it would cost more than 150$ for all the bearings and seals in the whole rearend. Most of the time there is nothing wrong with whats there already. In stock form a 9" will take 450-500 HP without breaking a sweat.

Shagwell

Sonix - some rears were cast iron, some cast steel. The earlier the model, the more likely to be iron.

- I'm going to run a plate with two bends, roughly 45's, across the housing. 3/16-1/4 thick plate about 2-1/2 wide. It will extend out onto the axle tubes about 3" from the diff on either side. Then make cardboard templates to "fill" between the plate and the diff housing at the front and rear of the cross plate. Then cut plate steel (3/16 - 1/4 again) to match, which will then weld to the corss plate, the axle tubes, and the diff housing. Repeat for the bottom of the housing. The bracing will look similiar to a Strange 9" housing, but just be around a cast housing. Doing it this way will allow me to weld to the axle tubes about 3" per-side, for each plate, thus two one each side for the top, and two for the bottom. - For stick welding you'll have to use "rescue rod" which is made for welding dissimiliar metals.

Batass

So the ford 9 can handle considerably more power than the 8.5? Ok, I couldnt find anything other than the torque arm kit that was specific to our cars, but they had various sizes of spring pads and shock mounts. I didnt see any control arm brackets though, upper but no lower. Drilling the holes for the bolt pattern wouldnt be a big deal at all, but I imagine theres some performance axles somewhere that would come with the correct pattern. I may be shifting towards the 9".........

Batass

pn# CE-7008A is all the brackets and mounted to a supplied or bought housing. Its $359.00. For 600hp I'd get new axles and after looking at all the parts I need plus labor to set the gears, I'm looking at close to $2k. Damnit, I might be better off just buying a complete one. Unless you guys think that a stock 9" would hold up to 600ft lbs, on some sticky's once in a blue moon.

ede

i don't think any moderan rear is going to be iron, cars, trucks, tractors, and anything in between. i know the GM rears aren't.

Sonix

iTrader: (1)

define modern eh?

The 8.5" in question is most likely from a 2nd gen, ie 1980 ish. Would that be cast iron?

I can't think of any modern rear that would work nicely, ie, length-wise...

Shagwell

Would the hair styles, music, or anything else from the 80's be considered modern? - Something 20ish years old isn't modern.......

Sonix

iTrader: (1)

Well, how about a real answer then? A year perhaps?

Otherwise Shagwell and Ede have done nothing but dance around the problem - if he's going to use an 8.5" 10 bolt, then he's going to have to find a donor. I was suggesting a 2nd gen since the bolt pattern and length is perfect, but I mentioned it was a cast iron housing. Is a 2nd gen 8.5" Cast iron? Sounds like it is.
Anyone want to argue this now? Maybe some proof, or a "definately" would suffice?

Or, what year/vehicle 8.5" rear would be cast steel, and be around the right length, and be a good donor?

Batass

Well, if it is cast iron, it isnt hard to weld these days. It used to be very hard to fix iron engine blocks and manifolds, but there are special rods that you can buy today and do it yourself. There are much improved rods than high nickel. Now welding steel to cast iron, im unsure of, but any shop that does block repair could let you know. If I wasnt in Germany, I'd be calling right now.

ede

i was meaning not from the 40s by moderan. the 12 bolts from the 60s were steel.

chevyowner02

iTrader: (3)

Ok I found a 9' my it's free complet rearend out of a 64 Fairlane. but here's the problem it measures 59' outside to outside and 53'esh from BP to BP is ours 60' and 54'? or do I need a 60' and 54'?

chevyowner02

iTrader: (3)

anybody???

Batass

I hope this thread doesnt end yet, I'd really like to hear more about this. It seems this info is hard to come by and could make a good sticky for people looking for a cheap rear with some good hp.

Batass

Nevermind, I'm going with a Moser 12 from Spohn. I dont think im going to baby this car.

chevyowner02

iTrader: (3)

Well I'm not going to baby mine eather I would just like to know if this 9'' will work?

Batass

I dont know what BP is, but if its free and it seems like the measurements are close, why not ****** it?

bluegrassz

iTrader: (3)

He is meaning "backing plate" when he sayis "bp".

chevyowner02

iTrader: (3)

Yea bp is backing plate his over all is 59'' mine is 60'' just dont want to suck the wheels under the fender wells.

Batass

Wouldnt a one inch spacer fix that?
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Wait, half inch