Transmission service - Yes or No?

[Supercharged111]

It's a toss up. Going without a flush can keep one going that is in bad shape. You may have enough friction material in the fluid that once removed you notice a slip.

BS, there is no such thing as friction material in the fluid helping the trans along. There's clean fluid and dirty fluid. Old fluid is broken down fluid. This is the stupid banter that gets spread and people regurgitate it all the time and think they sound smart.

 

[Dr.Zoom]

Where does the clutch material go?

 

[Tavi]

Where does the clutch material go?

Filter

 

[El Tigre]

I certainly wouldn't re-fill with Dex III (technically no longer exists)... Dex VI supersedes Dex III,and is backwards compatible in all GM transmissions.

 

[Mike Napolitano]

Hey all -

Just picked up my new-to-me 1993 C2500 Suburban and am curious what the conventional wisdom is on servicing the transmission. It has a 454 and 4L80E with 145K miles on it and shifts very very well. The 1/2 is a bit firm when cold but everything else is butter. The fluid is kinda more light brown than pink, but doesn't smell burnt.

I've heard some who say that, if the transmission is fine and the mileage on the fluid is unknown, that it may just be better to leave it alone. It sounds wrong to me, but I don't want to tempt fate on this truck, either. So what should I do? Should I just drop the pan and change fluids and the filter? Should I flush it? Or should I not touch a dang thing and just keep driving it as is?

Sorry if this is the transmission equivalent of 'what motor oil should I use?', but it's been a bit a LONG time since I bought something pre-owned with a slushbox. I typically row my own on my older rides, and the newer ones I keep up with the maintenance from Day 1 to avoid this kind of stuff.

Mike

If the fluid is brown then flush the transmission fluid. You do not need a flush machine to do it, just disconnect the two lines at the radiator and attach rubber hoses to them and put hoses into a drain pan. Start engine and run until no fluid coming out. Shut engine and fill with 8 quarts of dextron 3 fluid and start engine, once engine starts hold brake pedal and while holding brake pedal move shifter through the gears with a slight delay in each one and the put it back in park. Check fluid coming out of hose, if it stopped the shut engine and drop pan and clean it, change filter and reinstall pan with new gasket and fill with new fluid and put a bottle of lube guard in it, it will help with the shifting issue and the bottle of lube guard you use is the red bottle

 

[MADSIN]

Don't flush pan drop and filter change will do the fluid can just get ild from sitting around too

 

[Supercharged111]

Don't flush pan drop and filter change will do the fluid can just get ild from sitting around too

That's fine if you want to leave 2 gallons of old, nasty fluid in there.

 

[DerekTheGreat]

Yeah, the fluid won't turn to crap if left in it's original container. Hell, the fluid in my '69 Plymouth was fine after sitting for 30 years, was still nice and red. With that one I just dropped the pan to swap the filter out and replaced what drained out with +4 ATF or whatever MoPar called it at the time. As I've said, in every case I've done that or a flush, it's only helped the trans, never hurt it, despite what all the crappy myths are. And I got plenty of those crappy myths jammed into my head from my dad as a kid. All he EVER did was replace things that broke or changed the oil. When I was gifted the Firebird it looked nice but was a mechanical disaster. Helped accelerate my mechanical know-how though haha.

 

[jsfrmsj]

I flushed the transmission at 150k, 180k on it now, no ill effects.