Broken rear diff question

[elninoalex]

I just bought a 90 Legacy Wagon AWD with a "broken rear diff". I'm going to be bringing it home tommorrow. Assuming that it is actually a broken rear diff(I bought this car for the motor only), what could I possibly expect to get if I force FWD with the fuse? Or if I pull the driveshaft? I just need to drive it about 15 miles home. Thanks.

Stephen

[Chiketkd]

Got four jackstands? To take the guesswork out of what's wrong with the car, why not jack it up at all four corners, start it up and put it in gear? Then you'll be able to see what's going on with the car.

I wouldn't crawl under the car to listen to any noises up close, but if you have a long hollow tube (like a broom stick), you can put it next to any areas where you hear sounds coming from and stay a safe distance away!

15 miles isn't very far, but it depends on how rough those 15 miles might be... Will you be on the interstate going 70+mph? Or on gravel backroads going up and down steep inclines? These will be harsher on a car with a failing rear diff, compared to driving on secondary roads at 35-45mph.

-Chike

P.S. You said you bought a '90 Legacy? I'm not sure if they came with an R160 or R140 rear diff, but if it is the later, they have the tendency to break easily with very little abuse. The difference in size between these two diffs is shocking to look at!

These are two pics that Green_eyed_lady snapped when Svxfiles and I did my first trans swap to 4.11 gears (did a second swap to 4.44's about a year later!). The 4.11 4EAT trans I bought came with a R140 rear diff, but I went with an R160 for obvious reasons...

R140 left vs R160 right:

[Manarius]

Originally Posted by Chiketkd

Got four jackstands? To take the guesswork out of what's wrong with the car, why not jack it up at all four corners, start it up and put it in gear? Then you'll be able to see what's going on with the car.

Wouldn't the car knock over the jackstands when engaging in gear?

[Chiketkd]

Originally Posted by Manarius

Wouldn't the car knock over the jackstands when engaging in gear?

On level ground, with all four wheels up in the air...

-Chike

[Manarius]

Originally Posted by Chiketkd

On level ground, with all four wheels up in the air...

-Chike

I know, and I've always wanted to do that. However, I'm afraid that the force of my car engaging in gear would cause the jackstands to tip over.

[elninoalex]

Originally Posted by Chiketkd

Got four jackstands? To take the guesswork out of what's wrong with the car, why not jack it up at all four corners, start it up and put it in gear? Then you'll be able to see what's going on with the car.

I wouldn't crawl under the car to listen to any noises up close, but if you have a long hollow tube (like a broom stick), you can put it next to any areas where you hear sounds coming from and stay a safe distance away!

15 miles isn't very far, but it depends on how rough those 15 miles might be... Will you be on the interstate going 70+mph? Or on gravel backroads going up and down steep inclines? These will be harsher on a car with a failing rear diff, compared to driving on secondary roads at 35-45mph.

-Chike

P.S. You said you bought a '90 Legacy? I'm not sure if they came with an R160 or R140 rear diff, but if it is the later, they have the tendency to break easily with very little abuse. The difference in size between these two diffs is shocking to look at!

These are two pics that Green_eyed_lady snapped when Svxfiles and I did my first trans swap to 4.11 gears (did a second swap to 4.44's about a year later!). The 4.11 4EAT trans I bought came with a R140 rear diff, but I went with an R160 for obvious reasons...

R140 left vs R160 right:

Unfortunately, The car is parked on a narrow city street in front of the seller's house so I can't really do a whole lot to it. I'm hoping just the fuse would take care of it. The seller might not be real happy if I drive off in his car that he thought was undrivable.

[Manarius]

If you don't stick the FWD fuse in (and the rear diff is really broked), duty solenoid C will go crazy and make the split 50-50 and you'll burn out the clutch packs doing that. If you stick in the FWD fuse, you should be okay. This makes the Duty Solenoid C ignore the speed of the rear differential and completely disengages the clutch packs. However, running FWD for long periods of time is a no-no because the clutch packs aren't meant to be kept like that. I think 15 miles is okay, as long as you don't race it. It's a 90 Wagon, so it's not going to be a racer...unless it's a Touring Wagon .

[elninoalex]

Thanks for the input you guys! What size fuse does it take, or does it matter?

[Chiketkd]

Originally Posted by elninoalex

Thanks for the input you guys! What size fuse does it take, or does it matter?

I recollect that the SVX uses a 10A fuse in the fwd slot.

It's located in the engine bay fuse box. The fuse box lid will tell you what type of fuse to use in the Legacy wagon though...

-Chike

[intelisevil]

Originally Posted by elninoalex

Unfortunately, The car is parked on a narrow city street in front of the seller's house so I can't really do a whole lot to it. I'm hoping just the fuse would take care of it. The seller might not be real happy if I drive off in his car that he thought was undrivable.

I'd love to see the look on his face as you drive away with his 'undriveable' car, maybe you can hide someone across the street with a telephoto lens . . .

Dan

[Manarius]

As I recall, it's a 15 Amp Fuse into the FWD slot near the right strut tower.

[benebob]

Originally Posted by Manarius

Wouldn't the car knock over the jackstands when engaging in gear?

Notta, I took our old tranny up to about 150mph on jackstands . Don't try it though!!! It isn't the safest thing in the world.

[Manarius]

That was probably on a lift ben. I'd feel much safer if it were on a lift, but I fear what would happen if I did it with the stands I have now

[benebob]

Originally Posted by Manarius

That was probably on a lift ben. I'd feel much safer if it were on a lift, but I fear what would happen if I did it with the stands I have now

Just the lift of jackstands fully extended on 2x8 shims to make it even higher. Wish my wife would let me put a lift in!!!

[oab_au]

Originally Posted by elninoalex

I just bought a 90 Legacy Wagon AWD with a "broken rear diff". I'm going to be bringing it home tommorrow. Assuming that it is actually a broken rear diff(I bought this car for the motor only), what could I possibly expect to get if I force FWD with the fuse? Or if I pull the driveshaft? I just need to drive it about 15 miles home. Thanks.

Stephen

Depends on that is wrong with the diff. If the crown wheel and the pinon gear have all the teeth, it may roll without jaming, but if the teeth are damaged, it will have to be an 'all up lift'. The FWD fuse won't change anything, all the bits will still rotate.

Harvey.