does anyone know how hard it would be to make aft4wd tranny a 3.9 ratio with the dr reducer gear??????

The FT4WD tranny from a late 80's RX has the D/R already, and when it's in low it's 1.2:1 reduction effectively turns your diff into a 3.9..... as for opening the trans and changing stuff out, it may be possible, but would be expensive, and requires some special tools.

 

GD

4.4252 final in low...its 1.196.

 

unless im missing something.

It is indeed alot of work and expensive. One was built a few years ago by a guy in Colorado. I remember it took 3 or 4 trannys to make one. I also believe they had to do some special machining.

 

Using a turbo FT4WD trans in low is not the same. They do not have the same displacement and will be a dog. I have seen 3.70 finals used in off-roading. Let's just say that by the time they got back home they were already installing a 3.90 trans.

 

So, to answer your question. Difficult at best. Expensive?..probably. Worth it?...hard to say. My suggestion would be to install a trans from an non turbo car from '85 to '88. I believe they started playing with the gear ratios after those years. Not for the better either.