auto trans oil and filter change

[loneranger]

I have changed the trans filter on my 90 350 SDL before and replaced fluid in the pan. How do I drain all or most the fluid out to replace it. Or is this a bad idea. I have an Acua RSX my wife drives and every Honda mechanic tells me never touch any thing or change oil in that tranny or it will fail . Seems strange to this old guy but times change.

[BoiseBenz]

My ASE transmission guy (Wayne, second-generation of Wayne's Transmissions in Boise) cautions against "getting out of hand" with flushing or other "excess" servicing options on these older units. His point is that aggressive cleaning will likely dislodge some residue and result in the valve body "having a stroke."

He suggests just changing the fluid that falls out of the pan, and the filter (that is, do NOT remove the plug from the torque converter in this instance). This results in net "cleaner" fluid, which will allow any deposits/accumulations to either harmlessly remain in place, or SLOWLY dilute/erode and become trapped bit by bit in the filter or be harmlessly held in suspension in the fluid.

He notes that about 20% of his rebuild business has had a Jiffy Lube flush within the past week.

Also note that Bill Heath, the diesel guru for my Suburban, cautions against ever even removing the pan of the 4L80E (a super-duper TurboHydramatic 400, with overdrive and electronic/solenoid valve body). A "service" to him means siphoning out of the dipstick whatever you can recover, and refilling.

YMMV.

[sixto]

There are separate drains for the pan and torque converter. Turn the engine in the direction it normally turns, a ratchet with 27mm socket on the crank pulley bolt works well, and look for the drain plug to be at the lowest point in the torque converter's rotation. IIRC in a 126 the guide rod mount crossmember has to come off or there's poor access and fluid will splash all over the place. FSM says to use new bolts but most folks reuse the bolts with blue Loktite after cleaning all the threads.

There's a method to filling the transmission if you drained the torque converter. Lots of discussion in the archives. How I do it: pour in 4 quarts or so, start the engine, add fluid in half quart increments (pour, pause, slowly run through the gears), until the transmission engages. For me this is a critical juncture because then I can back off the ramps. With the car level, continue in cup increments with the same pausing and shifting until the fluid is about 1cm below the lower mark on the dipstick. Drive 20 miles, make sure fluid on dipstick is too hot to touch, check and correct fluid level. YMMV.

James, on the '97 C2500 'burb 6.5 we got with 150K miles, I replaced the filter then flushed a couple of gallons through the cooler lines. Still okay 25K miles later. Bill Heath's advice would be more relevant if the fluid was in there waaay too long. It shouldn't be a problem if the transmission has seen proper maintenance. Flushing the transmission is another matter. I wouldn't recommend that particularly on a mistreated transmission.

Sixto
87 300D^2

[BoiseBenz]

Originally Posted by sixto

James, on the '97 C2500 'burb 6.5 we got with 150K miles, I replaced the filter then flushed a couple of gallons through the cooler lines. Still okay 25K miles later. Bill Heath's advice would be more relevant if the fluid was in there waaay too long. It shouldn't be a problem if the transmission has seen proper maintenance. Flushing the transmission is another matter. I wouldn't recommend that particularly on a mistreated transmission.

Sixto
87 300D^2

Bill personally suggested same even as I was installing a "crate" GM reman into the rig, with its factory fill of Dex6. The old transmission (191k odo total, but we bought the rig at 185k so who knows) should not have failed that soon, but due to a combination of circumstances, I had to drive it back "heavy" (~19k GCVW), with a trans code, and some slippage--through the mountains. Wayne had already done a Dex6 and filter service.

I personally can't see anything wrong with your cooler-only flush. Safe, sane, and consensual, methinks.

[Air&Road]

How long has it been since the AT oil and filter were changed?

[loneranger]

about 20,000 miles

[Air&Road]

Originally Posted by loneranger

about 20,000 miles

Heck yes, CHANGE it and KEEP changing it.

It's when they go 80 or 100 thousand miles, especially with lots of in town miles it gets iffy.

When you do it, drain the pan and turn the engine until one of the drain plugs is visible at the bottom and pull it to drain the torque converter. While the torque converter is draining, replace the filter, then replace the pan, both drain plugs and CAREFULLY refill making SURE you don't overill.

Transmissions that have been high miles without changes are risky. Occasionally changing the filter in a high miler will result in lost clutch materrial and the car won't move under it's own power afterwards. I've never heard of or seen this happen with an MB transmission, but it certainly could.

Many shops will not change fluid in a transmission that has gone a long time since changing. They are afraid of the clutch material going away resulting in the car not backing out of the stall and the customer blaming it all on the shop.

Unless you have been towing a 20,000 pound trailer back and forth across Death Valley for that 20,000 miles, you won't have any problems.