LENGTHEN a rear end??

**nativetalon** · 04-29-2010, 10:38 AM

Ok, i found an old rear end from a (1980? i think) trans am with rear disk brakes. I am hoping to fab it to fit on a 2000 ws6 T/A (7.5). The rear end out of the 80 model is 4 inches shorter than the rear in the 2000 model. The hoghead is 1" wider (shaft to shaft) and 2" thicker than the 7.5. I have heard of narrowing a rear but not lenghtening. Is this practical? Or will it work. If so, wat needs to be done? The rear end was free, so hoped it was worth a try. Thanks.

**pajeff02** · 04-29-2010, 11:01 AM

You could certainly extend the axle tubes and purchase longer axles. You would need a jig to ensire that everything stays in alignment or you would end up breaking parts and tearing up tires. If you wanted to be real dangerous, you could use the existing setup with longer wheel studs and spacers. Another option is a change in wheel backspacing if it would otherwise clear the inner wheelhouse. In the long run though it sounds like one big headache.

**nativetalon** · 04-29-2010, 11:15 AM

I think i can extend the axel tubes and they will be straight. But will it still be strong. Or will that create a weak point. Also with new performance ring, pinion, and axels will it be strong enough to hold around 650 to 700 HP?

**pajeff02** · 04-29-2010, 11:26 AM

At that power level, you need either a Dana, a 9" or Fab 9 imo.

**ntimid8r** · 04-29-2010, 11:31 AM

I don't think this is a practical thing to do. Why do you want to change out your existing rearend anyways???? The old adage comes to play here, "If it ain't broke, don't mess with it".

Quite frankly, in this scenario you're spending more money and time than necessary on a 7.5 rearend. Yes you can make a second gen rear meet the fitment specs for a 4th gen but why??? The 7.5 is not a "strong" rearend to begin with. I'm sure you can find a used, stock 4th gen rear on craigslist or wherever for a couple hundred bucks. Which would be cheaper overall than buying new axles, bearings plus fab work on the 80's housing.

Another cheaper alternative to get a stronger rear and not shell out a couple grand for a new, bigger and better one....is to locate a ford 8.8 rear. It can be modified to fit an fbody. I don't recall all the specs for doing that, I'd have to research the details but I've read of a few that have done it. An 8.8 is slightly stronger than our stock 7.5.

**ntimid8r** · 04-29-2010, 11:32 AM

Originally Posted by pajeff02

At that power level, you need either a Dana, a 9" or Fab 9 imo.

**nativetalon** · 04-29-2010, 11:39 AM

How much HP will this setup hold at the rear tires?

**ntimid8r** · 04-29-2010, 11:47 AM

Originally Posted by nativetalon

How much HP will this setup hold at the rear tires?

Every rearend varies due to mileage, gears and if it's with a manual or auto. But to throw out a number I'd say 400 tops!! But be ready to get a stronger rear in not too long.

**nativetalon** · 04-29-2010, 12:10 PM

The rear end from the 80 model looks so much bigger than a 7.5That's y i was hoping it was an 8.8. Or something like that. Figured since i already had it. And it was pontiac. That it would be a close mod and stronger. Especially with upgraded Axels and gears.

**nativetalon** · 04-29-2010, 06:35 PM

Hey, I measured both rear ends again today. The "bandit" style T/A has a definately larger hoghead and 3" tubes. Compared to 2.5 inch tubes on the 2000 T/A. What kind of rear end is it?

**Cutlass** · 04-30-2010, 02:43 PM

8.5" 10 bolt. Its the axle our cars SHOULD have came with. Its not the strongest thing in the world but Grand National guys are taking these rears into the 11s and 10s.

**nativetalon** · 05-01-2010, 09:22 AM

Originally Posted by Cutlass

8.5" 10 bolt. Its the axle our cars SHOULD have came with. Its not the strongest thing in the world but Grand National guys are taking these rears into the 11s and 10s.

Thanks. But how much will i have tied up in this rear trying to modify it? If i do the fabrication myself. I know i need axels and tubes. What else is needed? It has 373 gears and I have a JEGS cover to make it a little stronger. Will I have more in it than its worth? And what else can I do to make it stronger? And is there another route i can take that will be stronger for about the same price?

**Darren P** · 05-01-2010, 09:27 AM

Originally Posted by nativetalon

Thanks. But how much will i have tied up in this rear trying to modify it? If i do the fabrication myself. I know i need axels and tubes. What else is needed? It has 373 gears and I have a JEGS cover to make it a little stronger. Will I have more in it than its worth? And what else can I do to make it stronger? And is there another route i can take that will be stronger for about the same price?

does the 1980 rearend have a torque arm?

**Cutlass** · 05-01-2010, 09:36 AM

^^^pretty sure they don't

**nativetalon** · 05-01-2010, 09:39 AM

I guess what I'm saying is that I know the 8.5 is stronger than the 7.5. But by how much? A lot, or hardly any? I'm looking at dumping 500 to 1000 into it to make it as strong as possible. Am i wasting my time and money on this mod? The 9" or 12 bolts are what i would like to have. But, hard to afford 2500 to 3000 in a bolt in rear end. Should I save my money for a 9" or 12 bolt? And, if I plan to modify a rear end to fit. Is this the rear i should modify. Or do I need to look for a better one. Or can I buy a new one and modify it myself for maybe a little more than what i will have in modding this one?

**nativetalon** · 05-01-2010, 09:45 AM

Originally Posted by Darren P

does the 1980 rearend have a torque arm?

No it doesnt. But I have two 7.5" rears and they both have one. Cant i fabricate one to fit? Or just buy one for around 150 or so?

**Cutlass** · 05-01-2010, 02:34 PM

The question is how are you gonna mount the torque arm to the 8.5" rear end?? Thats just about impossible. You gotta be a good fabricator. Might be easier to convert the car to a 4 link.