Tranny Shifting Slowly.

[George7941]

This is on our company van, 1997 Chev G3500 6.5l diesel, 4L80E transmission, 280k miles. Transmission is original, never been touched.

I drain the transmission pan at every engine oil change(5k mi, pan has a drain plug) and pour in 3.25l of dino ATF and, every 40k mi, I drop the pan and change the filter.

Transmission has been flawless so far but now when shifted into D from P it takes a couple of seconds to engage and there is a similar delay from D to R.

Fluid looks new on the dipstick and is up to the full mark. It has been about 20k mi since the last filter change.

Should I try a filter change now in hopes of improvement or is it a lost cause? Is a rebuilt transmission the only viable option? We would like to keep the van for another couple of years. Is there anything that can be done without dropping the transmission?

 

[Gary Allan]

Does this occur every time regardless of trans/ambient temp? The only experience I have with delay in engagement was due to cold (visc) and I've only experienced it with one unit.

 

[mgm13]

I would try Auto-RX before anything else, I have had excellant results in my trans. It's $25 vs. $3000+ what have you got to lose by trying.

 

[George7941]

Quote:

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Does this occur every time regardless of trans/ambient temp? The only experience I have with delay in engagement was due to cold (visc) and I've only experienced it with one unit.

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It does not happen every time but it seems to happen regardless of temperature.

George.

 

[Gary Allan]

Curious symptom. Hard to isolate it here.

Wait a minute. This occurs in my jeep ..or did ..more than once. The converter has a check valve (the exact nomenclature escapes me at the moment) that prevents fluid draining out of it. It apparently didn't work perfectly (or so I reasoned). I'd have a delay in engagement until I idled it a bit. It went away when I put my deeper pan on and switched to synthetic fluid. I didn't have any other symptoms in operation. Shifts were fine and whatnot ..so I didn't give it too much thought.


Does this happen regardless of how long you're idling before moving the selector?

 

[jonny-b]

Try Auto-Rx. It should solve the problem. Then you should start using a synthetic ATF-oil(Amsoil,RP,Redline is OK).

 

[punisher]

If the filter is clean and the pump isn't sucking air/cavitating, my vote goes for a pressure loss due to a seal or cracked apply piston. Hook up some pressure gauges and see if pressure is in spec. If pressure is off spec, fix it before any hard part damage is done.

 

[George7941]

I just talked to the person who drives the van. The transmission only acts up when the van is not moving. Say the van stops at a stoplight. Then, when the throttle is applied to take off, the van does not move for about a second and then takes off with a jerk. This happens whether the transmission is hot or cold, though the delay is longer when the transmission is hot. It happens every time. Once the van is actually moving the transmission acts normally.

I hope this helps in narrowing down the problem. Thanks.

George.

 

[-Clayton-]

At 280k it's probably in need of a rebuild.

 

[VK56VD]

try some synthetic atf like someone has suggested. it may or may not work but worth a try. mobil1 synthetuc atf is easy to get hands on.

 

[pidster]

Get the line pressure checked.