Filter or flush and what is the best transmission fluid?


113,000 miles on 2002 Z71 Suburban. Got it from original owner and only the oil has been changed...no other fluids have been changed. Seldom off pavement.
If the torque converter has a drain like my previous ride I think I would choose filter. However the ATF looks and smells good so I might choose flush and no filter this time. It shifts perfectly and tows better than a 2013 with fewer downshifts on the Interstate.
Next, what is the best ATF fluid for highway towing a side by side?

 

When I bought my 01 to tow a 5000-lb trailer, I did a flush with Royal Purple max ATF. It's not cheap, but I immediately saw my transmission temps running lower. Takes 16 quarts.

FYI - if you swap in an HD or Esaclade cluster, you'll have a functioning transmission temperature gauge. That's what I did, to better keep an eye on the transmission.

Don't forget - the weak point on these trucks is not the transmission, it's the rear end,. Don't overload it, use CAT scales, and make sure it doesn't get too hot on long trips when towing in the summer. I replaced two rears in mine. One of the reasons I upgraded to a 3/4-ton Burb.

On the subject of axles - make sure you replace the fluids in those, too. 80W90 in the front, 75w90 synthetic in the rear.

 

I just used Valvoline Max life in my Avalanche with 119K.
Shifts better now.
Only did a drain and refill and filter.No flush

 

When I took my 07 Tahoe in for the transmission service at about 80k miles, the service writer at the dealer said I should only do the filter and fluid, said flushing can bring on more problems then solve... I agreed...

 

Then when your transmission goes Tango Uniform at 100 K miles, they will tell you that you should have had it flushed.

 

I flushed at 85k. Truck now has 187k and the transmission runs/shifts perfectly. I've dragged a 7,000-lb trailer ~15,000 of those miles, heavy enough that I've blown out two rearends while towing it.

Oh, and most of the time, I'm driving the truck like I stole it.

 

Don't forget that a BG service on the transmission or differentials provides a significant warranty.

 

I'm sorry, what is BG?

 

BG Products, Inc. | BG Products, Inc. is dedicated to making vehicles last longer and perform better in the meantime.

 

use dexron fluid. it has the proper friction co-efficients the clutch packs are specifically designed for...not some aftermarket blend that works for everything.


Fluid can look ok on the dipstick but be bad when you drop the pan and get a look at a large volume of fluid.
Since the maintenance history is a mystery do both...Drop the pan, change the filter, then get the fluid exchanged by a machine that does not reverse flow or pulse pressure the system. After that do just fluid exchanges at the recommended intervals.


We sell the entire line of BG products at our shop. Some tranny rebuilders think its snake oil... and don't believe in any brand of trans conditioner fluids. I don't have the data to support or deny how it works. I don't use them; on a perfectly working trans, why add something that could swell O-rings and seals.


there is no convertor drain