Tranny flush 4l60e

[98sierra4x4]

Hi I just bought a 98 sierra with 145,*** miles on it and was wondering if a tranny oil flush would be a good idea or bad idea.

Also is synthetic oil in the trans a good idea?

 

[98_k1500]

Im gonna say bad idea. I bought a used trans and decided to change the oil and filter in it before i put it in my truck. I should not have messed with it. 900 flawless miles, then out of nowhere lost overdrive. Its better to leave an unknown condition trans alone.

 

[Ckeene]

Drain the pan and change filter. But do not "flush" the transmission.

 

[1998K1500]

Im gonna say bad idea. I bought a used trans and decided to change the oil and filter in it before i put it in my truck. I should not have messed with it. 900 flawless miles, then out of nowhere lost overdrive. Its better to leave an unknown condition trans alone.

I'll second this. Generally the rule of thumb with a transmission that hasn't had the trans fluid regularly flushed and taken care of (or if you don't know how it has been maintained) just leave it alone.
If you know it has been regularly done, it would be best to continue to do so.

 

[poncho62]

This question has been ongoing it seems as long as there has been automatic transmissions....I think if new fluid ruins a transmission, it was likely on its way out anyways.

I bought my 97 last year, with about 130,000 miles....was sure the fluid had never been changed, was sort of brownish. Drained pan, changed filter and added new fluid with a can of Lucas Trans Fix....Been good ever since.

 

[SkyHighColorado]

This question has been ongoing it seems as long as there has been automatic transmissions....I think if new fluid ruins a transmission, it was likely on its way out anyways.

I bought my 97 last year, with about 130,000 miles....was sure the fluid had never been changed, was sort of brownish. Drained pan, changed filter and added new fluid with a can of Lucas Trans Fix....Been good ever since.

ill 2nd this. They say its because the new fluid will break loose sediment and get stuck in the passage ways for the fluid to flow and cause a failure. I just serviced my 4l60e 325K miles and I don't know when it was last replaced but I got the truck with 260k. Fluid was low and old when I bought it so I just dropped the pan and changed the filter and slapped it back together and it drove perfect for a awhile then it would start to shift hard into 2nd when it was cold. I dropped the pan again and replaced it with a deep pan and new filter. Just last week it started shifting very aggressively like a shift kit so I ran the codes and got 82 for a bad solenoid 1-2 shift. I dropped the pan and swapped out all the solenoids I could and the pressure sensor. So far it has performed better than ever.....time will tell I suppose.

 

[VCaddy]

Drop the pan, change the filter, and refill with Dexron VI. You can get a look at the pan magnet, see if all is well inside. Any trans that blows up after a fluid change was already on it's way out, just a coincidence.

Avoid those "power flush" machines.

 

[98chevyz71]

The po of my truck flushed the trans and it lost od with 130k miles

 

[98_k1500]

I have seen this happen on a E4OD trans also, worked perfectly, owner insisted on changing the fluid and filter. Few miles later, it lost reverse, and progressivly lost every other gear. I never believed it would hurt anything until i saw it first hand, and im really not sure what it does to a trans, but i'll never do it again. If the fluid is very dark, i'd agree that the trans was probably on its last leg anyway.