subiemech85 Posted December 4, 2008 Share Posted December 4, 2008 and now I'm considering the posibility of converting 3.9 d/r to 3.7 d/r with front lsd as a bonus I really want the LOW 1.59 is is possible, and what parts are required from what donor? Link to comment Share on other sites More sharing options...
GLCraig Posted December 4, 2008 Share Posted December 4, 2008 (edited) So let me get this straight, you want to take a d/r 5-speed with a 3.9 final drive, convert to a 3.7 final drive and keep the 1.59 low range? Well if that's what you are after, it can probably be done using parts from a d/r 5-speed and a s/r 5-speed with 3.7 final drive. The key piece in all of this is the output shaft of the transmission. At 1 end of the output shaft is the pinion gear at the other end is a set of splines for the transfer case drive gear and in the middle are the driven gears, 1st/2nd syncro..etc. You are going to need to disassemble the output shaft from both transmissions and compare these two shafts. You are going to need to use the driven gears and syncro from the 3.9 transmission. It's very unlikely that the 1st through 5th gear ratios will be the same between the transmissions and the syncro is likely to be match to the shift fork. Obviously you will need to swap the ring gear and correctly set the backlash with the right combination of shims. (note the RX and xt6 transmissions are setup differently) Another option is to find a d/r 4wd transmission that already has a 3.7 final drive and swap the low range gear set from a 3.9. This transmission was found in some 85 turbo sedans and in the 86 RX sedan. Or do basically the same thing with a 87+ RX transmission. Edited December 4, 2008 by GLCraig Link to comment Share on other sites More sharing options...
The Beast I Drive Posted December 4, 2008 Share Posted December 4, 2008 The RX d/r lo gear isnt as low as the 3.9 d/r. Ive been thinking about this too, about taking an RX case and puting 3.9 or 4.11 gears and the 3.9 low range gearset into it, so i would have the torquey RX gearset ratios, 4.11 final drive, REALLY low low range, and locking center diff. I dont know how feasable it would be to do though, could end up being an expensive failure, or an epic success! -Bill Link to comment Share on other sites More sharing options...
mcbrat Posted December 4, 2008 Share Posted December 4, 2008 why don't you just put the LSD into a 3.90 diff? I have an open diff that you can have free when you get the LSD.... Link to comment Share on other sites More sharing options...
The Beast I Drive Posted December 5, 2008 Share Posted December 5, 2008 the 1-5 gears on the RX are a closer ratio than the standard d/r, and the final drive ratio before it goes to the diff is lower. Link to comment Share on other sites More sharing options...
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