- 4.30 ratio open diff I believe out of an automatic
- JVAB diff kit, this is the kit that requires new holes drilled in the trunk area for extra support
- Supra mounting flange, u-joint and weld yoke. These parts were sourced from powertrainindustries.com
(1) Okay, so very straight forward. Remove driveshaft and old diff. I left the axles in the car and just tied them up to the sway bar. I did not remove the sway bar for this swap.
(2) Bolt the two lower brackets to the subframe, make them finger tight. When you go to install the diff you want a little bit of wiggle room in these brackets but if the bolts are too far backed out, they will contact the diff during installation.
(3) I took the rear diff mount and loosely bolted it to the car, the bolts holes are slotted and the bracket should be placed as far rearward as possible.
NOTE: the mounting bosses on the diff cover are different heights. The taller one must be machined down to match the lower one. I had the guy at the driveshaft shop take it down for free. JVAB also offers pre-machined covers on an exchange basis if you so desire.
(4) Bolt in the diff. Its a heavy mother. Don't hurt yourself. Two bolts in the rear through the diff mount and then two bolts up front with the machined spacers.
(5) Once everything was in and tightened up I set about drilling the trunk area for the additional supports. 4 bolts with weld nuts are supplied with the kit, I only used two because as you will see in the pictures the other two nuts need to be machined to fit inside the frame channel. I don't forsee this being a problem. You must use at least two. Forgoing this step and relying only on the small bolts from the factory mounts will most likely rip out. Center punch the holes, and drill them out. Then cut small access holes in the trunk floor and fish the weld nut in from above. It's very easy. Took me about 10 minutes to do both.
(6) Once the secondary mounts are installed you can bolt on the cv adapters. I used a small amount of hylomar to seal them to the drive flanges. You will need the 14mm hex nuts from the supra diff, the mounting face for the cv joints is as close as possible to the nuts. I had to use a crescent wrench to tighten them up. I would imagine that ARP style 12 point nuts for head studs would be a good application for this.
(7) Bolt up your axles install your new driveshaft and enjoy.
Comments:
(1) The cv adapters are dual drilled for the factory cv's and the cossie cv's. When you bolt up the factory cv's they do not completely cover the cosworth bolt pattern. I imagine some grease will come out of these holes. A solution would be to get the press in caps for the inside of the cv's that come on most newer axles.
(2) The driver side lower bracket needs to be trimmed to fit. The flange on the beam bends out at about 30 degrees and the bracket needs to be relieved around it. Takes a minute with a hacksaw or whatever.
(3) I used a 1351-20 u-joint for the supra flange. The spicer number is 5-1510X. The weld yoke is 1326-20. These are powertrainindustries part numbers. I imagine the weld yoke will need to be machined to fit the driveshaft. Both pieces were $50. The overall length of the driveshaft will not change.
(4) I will have to clearance my exhaust for the diff to fit. It mounts below and to the outside of the beam flange so depending on how close your exhaust comes to your beam you may have clearance issues.
(5) I was able to keep all 4 bolts in the original diff mount location. I put them all in for piece of mind. Do what you will.
(6) I have seen kits that include a piece for the upper mounting location in the beam. The kit I purchased did not have this piece. I may fab something up later to pick up this point, but my car is about 160 hp NA so I'm not worried about it currently.
Here are the pictures.
