I am looking at a 93 rx7. The car already has a kaaz differential and chromoly axles.

Currently the car has 15 x 26 x 10.5 ET streets. What would it take to run 28 inch tall slicks? Do I need a mini tubb or rolled fenders?

Also how long do you think the oem rear end with upgrades would work being a powerglide? I know a lot of people are upgrading them, but many cars are still using a stick transmission.

 

That is a hard question to answer. There are a lot of variables that could keep it alive or kill it on the very first run. From the research I have done it seems that it will last a little longer with an auto vs mannual. The axels and kaaz prob wont break but the diff itself is now your weakest point. The weak points of an FD drive line are trans, lsd, axels, and diff....not necesarily in that order. Since you have fixed all of the other weaknesses I would say the diff casing is on the chopping block. You could do like a lot of other folks and replace it with the 03 cobra IRS and mod the sub-frame. I would just run yours till it breaks and then replace it. But deff put a brace on it or something to stiffen it up a bit.

 

You don't need a 28" slick unless your putting down over 1000rwhp. Stick with what you have. Its more than enough tire. The tranny you like will require alot of r&d to work correct. You may want to stick with shifting gears. Its more fun anyhow

 

Stock FD rear will not last long at all. Mine lasted one pass and stripped out the spider gears. Highly reccommend the 87-88 turbo 2 lsd as a replacement(search it under 3rd gen for a write up) ive made about 10-12 passes and about 6 10 sec passes and held up very well. But the kaaz should be fine. I have 475rwhp and launching at like 7k(no two step). Im also still using the stock 5spd and 26x10.5x16 et streets(bias ply).