I can't seem to find this answer.

Is the 90-92 28 spline axle compatible with a 4th gen housing if you shorten the housing? Reason I ask is it seems to cost about 150-200 to get the housing shortened and rewelded but new axle shafts are about 150 each, I can find used axles for cheaper... though typing this I realize that isn't a huge price difference so maybe not worth the hassle.

The flip side of this question is if I start with my 89 housing and buy new 28 spline axles can I transplant the differential components from the 2000 over?

I don't really want to shell out the $$ for a 9" other built axle since I already have a 4th gen axle and I don't plan on going much above what the stock ls1/t56 puts out anyways.

This is going back into my 1989 if that wasn't clear.

 

If you don't have the money for an upgraded aftermarket rear end you'll be stuck swpping in new rear ends so I wouldn't sink any money into an f-body rear. Well, maybe a cover girdle.

Alternatively, if it only costs you $150-200 to have a housing shortened and rewelded why even fool around with a ten bolt? Pull an 8.8 ford rear end from an explorer/grand marquis/ranger/mustang and have a set of F body tubes welded on. Then there are several threads online detailing how to go about making a torque arm mount. Change the driveshaft's rear joint and you'll have a rear end capable of 400 hp in stock form.

 

Do you need both axle shafts? If not, I'd buy one and call it a day. No reason to replace both if only one is bent/bad. Like the previous poster said, not worth sinking too much money into a factory 10 bolt because they leave a lot to be desired. There is nothing better about a 4th gen rear besides the brakes, which can be swapped onto a 3rd gen rear pretty easily.

 

Nothing is bent just curious if the parts are interchangeable since they are both 28 spline (well 90+ are). Its my understanding that the axel shafts can't be shortened is why I would buy new shafts. The posi in the 89 never worked well and the 2k donor car I bought for the LS1/T56 has 96k on it and the posi works real well and is a better better gear ratio. I'll be $4k into the ls1/T56 and suspension parts when all is done. Since I have no plans to drag race it. The 10 bolt is sufficient for my plans, if I grenade it then I'll bite the bullet and put in a 9" or 8.8.

The 2k donor runs and drives but has a non rebuild title so I know everything works.

I can do what I want for $500 and with a stock LS1 it will be sufficient for now.

 

Street tires and an ls1 can break a ten bolt, you can watch videos of it on youtube. Put on a set of good tires and it's a time bomb with aggressive driving. Save up for an aftermarket or frankenstien 8.8 rear and don't shock the drivetrain.

 

You seem to have answered yourself.

 

I plan on doing it but still need to know if the 90-92 axle shafts are the same diameter and spline spacing etc to work with the shortened 4th gen housing and stock 4th gen diff, or if I need to order new shafts. I'm guessing since the spline count is the same knowing gm it will work. Figured I would attempt something out of the norm on these builds.

I didn't really want the 10 bolt isn't worth it debate, usually when one breaks it's because of play in the diff which hammers the gears... 1000s of 4th gens with the 10 bolt and ls1s seem to work ok with the combo. If it comes to it doing a built 9" isn't something I can't afford but since I don't need that strength in this setup I would rather pour that money into the tanks of my Cessna.

i was trying to avoid pulling the shafts until I was ready to actually to do that part of the build but that may be the only way to know for sure.

 

28 spline is 28 spline, diameter is industry standard, so that the tooling that cuts or rolls the splines is all the same. The diffs are interchangeable from 3rd to 4th gen, so that settles that.

One misconception is that hammering of the gears is what breaks these rears. It is one factor. The other is the inherent weakness of the small ring/pinion gear and housing. The Pinion gear "climbs" the ring gear through housing flex, that is where a lot of failures occur, sometimes they just start to whine, sometimes that leads to sloppiness that causes teeth to break. that is why some use a solid crush sleeve, to prevent this exact thing, to stiffen the shaft of the pinion gear by not allowing the softer crush sleeve to flex on one side which lets the pinion gear climb the ring gear. A lot of the 9" strength is from the bearing on the nose of the pinion gear that prevents the pinion gear from climbing the ring gear.

 

Im working on a 8.8 now for my car check out the size difference from the 8.8 to a ls1 7.5

 

why not swap the gears/posi into the 3rd gen housing. Problem solved.

If you don't need the gears, the posi is a direct bolt in place of your nonworking posi unit.

 

3ed gen is the 2.x gear ( I knew the number 10 years ago lol)... Maybe good for a top speed run but not daily behind the t56. But now that I know the parts are interchangeable I may do this. I've always avoided diff work, so if nothing else I'll get to learn something new... Just need to pick up some 28 spline shafts since I'm sure the 89 has the 26. And new disposals and crush sleeve... Though may be cheaper to shorten the housing I'll have to look up parts.

It took me longer than it should of yesterday to get the wheel locks off the donor car ... 2 came off real easy with hammering old undersized sockets on them.. one wheel didn't have one... The other one I had to weld a bolt to the lug... The bolt shaft started to twist before it came loose... Kinkof surprised I didn't break the stud.

I've decided im going to get it running on the stock rear then deal with this project... Or go the expensive but easy route.

 

I think they went to 28 spline axles 87-88 for when they brought back the 350 tpi.

 

They went to 28-spline axles in the 10-bolt in 1990; a random few, probably ones with certain less common ratios or the like, that they didn't have a billion of already built up and sitting in stock on the shelf waiting to go into cars, changed over in 1989. A random few 90s might have got the old stuff, until stock was exhausted, I'm not sure.

It had NOTHING WHATSOEVER to do with 350 or TPI. S trucks, for which of course neither 350 nor TPI was an issue, made the same change in the same years.

 

The reason for the 4th gen axle swap is mostly related to wheels and/or brakes, not strength. The 4th gen housing is no stronger, just longer, with more unsprung weight. That helps nothing. But it allows positive-offset wheels without spacers. Better to just use a third-gen-width axle assembly and choose wheels accordingly.
You can put the 4th gen gears in the 3rd gen housing with just a common ring-and-pinion installation kit.
The best thing about these axles, including both gens and non-Camaro versions, is that they really consistently take a 0.035" pinion shim, so you generally don't have much trouble from gear swaps.
I've found threads in here of guys running 1.4-second 60-foot times on the '91-'92 versions, it seems they're running automatics and drag radials. On the other hand, there are also reports of guys breaking the '91-'92 versions with stock 305 / automatic combos on cheap tires.
Every dollar you put into a stock axle is a dollar you could put toward an upgrade now instead of later. It costs more to do it twice. Sell your junk before you break it, once broken it becomes worthless scrap. Plus upgrading now brings peace of mind. That's worth something.

 

For the money, a moser housing and axle package is about a grand. Toss in a center chunk from the junkyard and you have a strong cheap axle.

 

Moser 12 is $1,400 without shipping. Hawk's wants a crazy $1,300 just for a bare housing 8.8

 

Where can u get a moser 12 bolt for 1400? Sure it's not just the housing axle package or something?

 

Yea thats what i mean moser housing and axle package for $1,400