This is a project I started last summer and finally had a free weekend to finish. I wanted to upgrade my rearend for my 1986 Trans Am. It is to be used for bracket racing. I didn't want to spend big bucks on aftermarket. This works with a 9 bolt rear with 28 spline unequal length axles.

1. Find an inexpensive 9 in with a 28 spline carrier. All you need in the center portion of the housing and the 3rd member so don't worry about brakes, bearing end size etc.
2. Pull your 9 bolt out and dissasemble.



3. Next I built a jig out of scrap steel. I took some pictures of it when I built it but can't find them right now. I'll update this if I come accross them. Anyway it bolts to the lower control arm mounts and factory panard bar mount. Use an angle finder to measure the pinion angle and right this down for later. Now you will be able to to take a saw and cut the center section out of the 9 bolt leaving the the tubes still in their correct location.
4. Now you will cut the tubes off the 9 in leaving about 1" off tube coming out both ends of the centersection. This is to give you a nice area to weld later.
5. Unbolt one 9 bolt tube from the jig, slide the 9 in center section in place then slide the other tube in and bolt it back down. (The 9 bolt tubes are smaller O.D. than the 9 in and fit very nicely)
6. At this point all remaining parts will need to be stripped where the tubes overlap so they can be welded.
7. Set the pinion angle that you recorded earlier.
8. Turn the welder up and do both sides!
9. Paint
10. Now you can assemble it with the 9 in carrier (mine is 4.11 posi) but still used the 4 3/4 pattern axles with all the stock mounting hardware to put it back in the car! I replaced all the bearings, seals and studs also.




11. You will still need to weld a bracket for the torque arm. I have one from Currie I will be using.



* Notes - This isn't going to handle ridiculous power with 28 spline axles but it is a nice upgrade. Also the 9 bolt axles come close to bottoming out against the 9in carrier because it is wider so check this. Also this worked for me but measure yourself to verify it works for you! You should be able to use a 10 bolt rear to do this also but then you would have to get custom axles made. This however would give you the opportunity to upgrade even more with a 31 spline carrier and axle set.

 

Very cool more pictures??

 

that one falls right into the "why didn't i think of that" category!
excellent

 

I just pulled the brackets off the 9 bolt and welded them to the complete 9". I would have had a 9" rear for $100, but the posi was totaled after I tore it apart to check it. Good idea if you've welded axle tubes before and can keep everything straight.

 

So you're saying your 9 bolt axle splines are the same cut as the 9" axle splines? Just because they're both 28 spline doesn't mean they have the same angles on the cuts.

It's good to see you have some fabrication skills and made a jig to keep the axle tubes aligned but even then, the tubes may not be perfectly in line with the carrier bearings.

 

thats what i was gona say... they have to be perfect or ull be going through bearings very quickly. they use a special tool to center the axle tubes. it spins on and centers the tubes.

also u didnt really need to go 9" since ur still using the 28spline axles... would have stepped it up to 31 at least but i think your limited now bc ur running the stock tubes and ends of the 9bolt. i dont think u can run larger than the 28splines in the stock 3rd gen rears. so now u cant make too much power with those axles esp in bracket racing.

i just did a ford 8.8 swap, now i dont have to worry about breaking my rear good to see u think like me! im running the stock ford 28spline axles too but i can easily upgrade to 31 or 33 even very easily. But i heard that the ford axles are made of a more durable steel than the stock GM... think ford was the 1541 or something and supposidly its alittle better than the GM stock 28 spline axle material.

seen here, check it out
https://www.thirdgen.org/forums/tran...d-8-8-a-4.html

 

Another direction to go with it, this is nice though because cutting off all the brackets and lining them up is a pain. And the stock brakes and wheels go back on.

 

If the pressure angle on the spline was different the shaft wouldn't fit the carrier. I checked this before building it.

True that the best way to align the housing ends is buy using a good stick of cold roll that was ground and possibly chromed. Also you would need 4 adapters to seat it in the carrier's bearing saddles and the housing ends. But that is a good few hundred dollars worth of parts and this was free... As long as the rear wasn't bent you started with and make sure the jig fits well you'll be fine for something like this. I drilled the holes undersized then reamed to fit.

 

Like I said this is for a 12 sec bracket car. 28 spline axles will be more than adequate and now I have infinite gear selection, no c-clips (10 bolt only) and its much easier to work on along with the benefit of a much larger ring gear.