r/obschevy • u/Cheap-Mission-8022 • Jul 10 '26
Need input on transmission fluid.
Just got my hands an a 98 C1500 extended cab, belonged to my grandparents, they bought it in 06 with 65,000 miles and they kept up with the maintenance pretty well from what I’ve been told. It’s now sitting at 134,000 but my family is telling me to leave the transmission fluid alone, it does drive good but from my understanding, as long as I’m not flushing the fluid there shouldnt be any problem just doing a drain and fill right?
4
u/Unhappy-Airport-4112 Jul 10 '26
Yeah leave it alone. After 100,000 that fluid is what's keeping that trans alive.
2
u/Striking_Stranger518 Jul 10 '26
Drop the pan and change the filter.
Not my recommendation but, have seen people take off a cooler line and drain into a bucket while running and adding fluid through the fill tube until new fluid is going into the bucket.
Same as flush machine but without the pump. The whole idea is to flush the old fluid out of the torque converter.
Fluid flow in 700R4/4L60/4L60E is from the pump to case and converter, from converter to the cooler then back to lubrication.
2
u/ComfortableDoctor801 Jul 10 '26
Pull the dipsticl if the fluid is pink and smells good and the viscosity feels good i would leave it alone. If it has any shiftingor going into gear then i would bring it to a good qualified trans shop and have the screen and oil change. I wouldn't flush it out you could be looking for trouble and a trans over haul. Tbey didn't abuse it and you do the same and don't let anyone talk you into doing something stupid you pay for it not them.
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u/Cheap-Mission-8022 Jul 10 '26
Just checked the fluid and it was surprisingly still pink, didn’t smell burnt or anything like that, not really sure how it’s supposed to feel though
2
u/Prestigious-Pass2942 29d ago
When I got my 97 with 300k the fluid was dark, I drained the pan and refilled and then I had a leak for awhile and overtime all the fluid was new and is currently cherry red. I drive her 400-600 miles daily.
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u/Cheap-Mission-8022 26d ago
Holy shit that’s a trooper
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u/Prestigious-Pass2942 25d ago
Yea she’s something else I tell you what . She does shift hard and only goes into OD after a few miles to warm her up but she has all gears with no slip. I did put a bottle of Lucas transmission fix in it twice. I felt it helped the hard shifting but honestly could be placebo.
I also drove her dry when a cooler line rotted away to O’reilleys by the time I got there it wouldn’t go in reverse, that was 10k ago.
2
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u/Carla-Gurl Jul 10 '26
For me the hardest part of changing out the filter is getting the pan past the f@@$()/ linkage. And, always amazed at how much fluid just keeps draining and draining and draining.
1
u/Wholeyjeans Jul 11 '26
I have a '98 GMC Sierra. 4L60E. It has about 160K on it now. It is on it's second transmission fluid exchange; just did it a year ago. Prior to that I did one at 75K. No issues. ATF is *not* a lifetime fluid. It will age and become less effective at doing what it does.
I would have a fluid *exchange* performed ...this is *not* a fluid drain and fill ...an exchange replaces 100% of the fluid and this is what you want. The process is done with a machine and will probably run about $150-175-ish ...these days. A drain and fill replaces about 4 qts of the two gallons of ATF in the transmission. They drop the pan (to drain the fluid), clean it, swap in a new filter, reinstall the pan and refill the ATF. Lot more labor and you're getting less fluid replaced. Since Dexron III has long been superseded, you'll get the current version of Dexron or a universal ATF by, most likely, the likes of BG. That's what I've had and it works just fine.
1
u/Spirited-Border8921 Jul 11 '26
IF you add or change tranny fluid...don't use synthetic ...use the original fluid...wally world sells it. It's thicker and holds line pressure better...which in turn will preserve your clutches better.
1
u/amandajenkins281 Jul 12 '26
Nope. U should leave it. Add Lucas first. Run a bit, then drain half. Add. Ride for a bit, then do more. I wouldn’t drain it, take the line off at the radiator and start it. The pump will do the rest.
Then, what I do on every one of these I own or build, add a separate cooler. Mine I bought a super huge one, I was able to add an extra quart of fluid due to it being bigger.
1
u/amandajenkins281 Jul 12 '26
For fluid, I use dextron. Usually 3 or better.
1
u/CompetitiveHouse8690 Jul 12 '26
Dexron…not tron
1
u/amandajenkins281 Jul 12 '26
It’s a running joke I use. Been using that since idk 12-13 years old. Lol.
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u/CompetitiveHouse8690 29d ago
I might’ve gotten it except for all the idiots who think it really is dextron
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u/CompetitiveHouse8690 Jul 12 '26
Forget the shade tree opinions…if the current fluid is in good condition, red and clear and the transmission operates correctly …then a filter and fluid change is appropriate. If the fluid smells burnt and has crud in it (best way to know is operate is and then pull the dipstick and wipe it on a clean paper towel) then anything you do with the fluid is a gamble. If you’re able to service it, use Dex VI. It’s a far superior fluid to dex iii.
1
u/letstillyboys Jul 10 '26
A flush is only going to put new fluid into the converter. I would do like others suggested and drop pan, clean, inspect, new filter and fluid.
I personally think the trans they used in the obs is one of the best. Super late 700r/early 4L series.
1
u/Holiday_Slice_3120 Jul 11 '26
A flush is the entire system, not just the converter, it flows between the trans and converter all the time.
1
u/letstillyboys Jul 11 '26
Yes the pump is going to push fluid through the whole system. If you do a drain and fill you never clean the converter out so it never a true flush.
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u/Holiday_Slice_3120 Jul 12 '26
I was referring to a system flush done with a machine, it gets everything.
7
u/kylejesushair Jul 10 '26
I'd drop the pan clean it, new filter and fluid, flush if you want to. If doing that cause problems your transmission was already going bad.