I recently bought a 94 2500 gmc 6.5 turbo diesel auto 4x4 with 232k miles. I took it to a oil change shop and they said I should not change my trans fluid, as it adds grip to the worn out trans. The fluid is "UPS" Brown, maybe a little lighter. It drives great, I think I felt a knock at a stop sign once or twice, I was hoping it was something in the truck bed.
I was planning on driving 2000 miles and pulling a 7000lbs trailer 2000 miles back. No major hills. With alot of mild-heavy towing regularly, after that.

I thought I read something about an additive that adds grip.? I just can't stand the thought of leaving brown fluid it in.

I really don't feel like it's past the point of no return.

Anybody?

adds grip? possibly.

new fluid will loosen all the grime inside the trans, and you'll probably end up with a plugged valve body.

with that many miles, i'd leave the fluid alone. just top off as needed.

6 of one, half dozen of the other IMO. If you have a drain plug I would consider draining out maybe 2 qts and replace that and run it for a while. That way it isn't such a "shock" to the system. If that goes trouble free after a couple thousand miles, then drain whole pan and replace. With that many miles and fluid condition, it wouldn't hurt it any worse than leaving all old in there.

I think trannies are alot like underwear, you want to change them before they get brown stuff in them. And if your shorts or tranny already has brown stuff in them, its time to change it. If its brown flush it down.

I just don't understand how broken down dirty fluid, "grips better" than new "thick" "elastic?" fluid.

If junk bouncing around in there helps at a later mileage, why not when they are new?


Lets say... I put the new fluid in and it starts slipping. Is there an additive to thicken it up... dirt/metal shavings?

I had missed the comment about the valve body....

Multiple flushes/changes wouldn't fix that? .. No cleanout?? <-- I'm a plumber.

Actually brown shouldn't be alarming. Its the smell. Burnt is burnt. However changing the fluid is always a good thing. I will always recommend manually flushing the transmission.

Changing the fluid or flushing on a high millage vehicle can loosen or dissolve sludge buildup around seals which will then begin to float away. This leaves the worn out seals unsupported and leaking. So the car owner takes his car into a shop for a flush, then drives it away. It begins to slip or not shift properly. What does he do? He takes ir right back to the shop and blames them for screwing up his perfectly good 200k mile transmission and wants it fixed. That's why a good mechanic will politely send him on his way.

personally i don't change fluid in a trans unless it got contaminated . changing bad fluid doesn't repair anything. if you changed it while nice and bright red then i guess it would be ok. i have gotten 100k on two 700r4 and never changed the fluid until the trans was changed. been doing limited trans work since the late 70s.