Mid-90s AWD Legacy 4EAT diff question(s) ...

[Mad Mike]

The front differential in my STREET-DRIVEN 94 AWD Legacy wagon with 4EAT auto tranny has shed teeth at 170k miles but I have a FWD/auto trans Legacy sedan parts car (sans engine but with half the miles) sitting on a trailer waiting for its trip to the crusher. Based on available research the torque split in the AWD wagon is 90/10 (which would explain why the thing has acted like a FWD car on ice/snow) and the front diff's gear ratio is 3.90/1 while the ratio in the FWD car's is reportedly 3.70/1. I read that there's some kind of gearing in the transfer case that allows the wagon's rear diff ratio to be 4.11/1 so I'm a bit concerned about replacing the wagon's diff with the 3.70 from the sedan. Since using parts at hand rather than spending money is the TOP PRIORITY I'm juggling two plans of attack and would appreciate expert opinion on which will likely work best. Of course, either will require yanking both transaxle assemblies so the decision boils down to replacing the broken diff with the lower ratio one while retaining the AWD arrangement (counting on the 90/10 torque split from a really worn center diff to effectively negate complications from the gear ratio mismatch) or replacing the entire AWD transaxle assembly with the FWD one and just leave the rear diff driveshaft-less. I'm leaning toward the former since I have new front halfshafts under the wagon now and will need to replace at least one of those from the sedan (yes, they are different for some reason) and I'm not contemplating FWDing the rear half of the car since the wagon has new rear struts that are different from the sedan's (unless there's a market for the rear diff/halfshafts/etc that would offset the work swapping stuff and the cost of new rear struts).

 

So whattaya think? Am I likely to regret bombing around in a wagon with a 3.70 front diff/AWD/minuscule F/R torque split or should I create a true FWD wagon that burns a little extra fuel hauling around & spinning the rear third-member assembly?

[johnceggleston]

the ring gear and pinion in your 94 lego auto are both 4.11, front and rear, not 3.9.

 

there is no gearing in the transfer case, just the transfer clutch to send more or less power to the rear when needed.

 

your cheapest solution is to swap in the FWD trans and leave in the rear diff unused. (you will likely have an AT Oil Temp light blinking at start up but it should drive ok.) when you have the time and money, fix or replace the front diff in the AWD trans and swap it back in.

 

click here:

94 lego auto AWD front diff item

 

item #3.

Edited March 22, 2010 by johnceggleston

[bheinen74]

there were a few Legacies at the 1200 S Santa Fe in OK City pick in pull jy this weekend. You should be able to get what you need there if you need something. some were FWD some were AWD.

[Mad Mike]

Thanks all! The plan definitely looks to be turning the car into a FWD machine (which more than works for the tasks I have to complete with it - especially since winter is finally done) with all the AWD gear left in the back half. After that, who knows?

 

Thanks again!

 

Mike ...

http://www.realautosport.com