Rear Differential and Trans Fluid change

[97v6firebird]

I am sure this have been asked many times before, but is it better to take it somewhere to have the fluid changed in an automatic so they completely flush along with changing the gasket/filter ?

Also, what about the rear differential ? My car has 118k on it and the rear end fluid has never been changed. This seems fairly simple to do but what fluid do you suggest ? I guess my biggest concern with this is that it has 118k miles and it is extremely rusty from the chicago winters and I don't want to break any of the bolts.

[cam98aro]

Re: Rear Differential and Trans Fluid change

i wouldnt do a flush on an auto tranny with that kind of mileage

just drain the pan, change the filter, and add what you need to

for the rear diff.. if your gasket is fine, use a hand pump to pump the fluid out, and add some 75w90 to it

check the codes on your door to see if you have a posi, if oyu do, you will also need to buy a tube of additive.. if not, just straight gear oil

edit* i mean LSD

[97v6firebird]

Re: Rear Differential and Trans Fluid change

i wouldnt do a flush on an auto tranny with that kind of mileage

just drain the pan, change the filter, and add what you need to

for the rear diff.. if your gasket is fine, use a hand pump to pump the fluid out, and add some 75w90 to it

check the codes on your door to see if you have a posi, if oyu do, you will also need to buy a tube of additive.. if not, just straight gear oil

With the trans fluid, is the thought that the older fluid is actually better because it provides some friction whereas the new would be too slippery and may cause problems with that many miles ?

Also, I don't really know if it has been changed before. I believe the gasket was leaking at one point and was fixed under warranty, but can't remember for sure. Also, I had the rear main seal replaced because of a bad oil leak and they had to drop the transmission. I guess I assumed they drained the trans fluid if they dropped the transmission, would this be correct ? Sorry if this is a stupid question, just trying to learn and do the proper maintenance.

[cam98aro]

Re: Rear Differential and Trans Fluid change

With the trans fluid, is the thought that the older fluid is actually better because it provides some friction whereas the new would be too slippery and may cause problems with that many miles ?

Also, I don't really know if it has been changed before. I believe the gasket was leaking at one point and was fixed under warranty, but can't remember for sure. Also, I had the rear main seal replaced because of a bad oil leak and they had to drop the transmission. I guess I assumed they drained the trans fluid if they dropped the transmission, would this be correct ? Sorry if this is a stupid question, just trying to learn and do the proper maintenance.

its because ATF is a high detergent fluid, when you change it, you are getting a bunch of dirt and grime out of your transmission, this dirt will get pumped through your transmission and can easily ruin it.. also, when it takes the dirt out, you get metal to metal contact, (since the dirt fills in the wear spots) and causes even more wear to the transmission

they most likely did drain the trans fluid, but im sure they didnt actually flush it out, when you take the driveshaft off, trans fluid is going to pour out everywhere.. so im betting they just added what they lost and didnt bother to even drop the pan.. same with the torque converter

[dobie]

Re: Rear Differential and Trans Fluid change

This is what I learned from rebuilding my 4L60E. If the fluid smells burnt don't change it because the clutches are already slipping and new fluid will make it slip worse. If the fluid is dirty but not burnt change it because it's normal wear and if you let it go too long valves will start to stick causing slippage, burnt fluid, and expensive rebuilds.

Sticking valves in my valve body are what caused the demise of my 4L60E. When I pulled the clutch packs for 1st and 2nd gear the friction material was mostly gone and the metal part of the clutches was blue from the heat which is where the burnt fluid came from.