96 Chevrolet Transmission Pressurizing

Aaron Ford · May 2, 2011

My brother has a 96K1500 with a 350 and a 4 speed automatic. It shifts fine when cold and when it gets hot begins to shift hard. Stopping and relieving the pressure by unlocking the dipstick will fix the problem for a while. If left loose, it will shift fine for the entire trip. The fluid is light brown with a slight odor and has not been changed recently. What gives?

Thanks,
Aaron

GregCO · May 2, 2011

Vent plugged?

Greg

Richard H. · May 2, 2011

Flushing the fluid and changing the filter would be a good start Aaron.

Super Steve · May 2, 2011

had it in the mud? my guess is also the vent

Allan in NE · May 2, 2011

Naw,

Think that theory is in your head. If it did indeed have case pressure, it would be puking itself empty all under the pickup. Besides, case pressure or the lack thereof has absolutely no effect on the operation of the transmission.

Change the fuel filter because your tv pressure is too high due to increased reading seen by the PCM received from the throttle position sensor.

In other words, the brain thinks you are under hard acceleration; hence the hard shifts.

If a clean fuel filter doesn't straighten it out, get it to someone who knows what he's doing. Brown oil is never a good sign.

Allan

Aaron Ford · May 2, 2011

A trip fully loaded into the heart of the Appalachians led us to the dipstick tube trick. It has worked every time. Just not sure what is causing it. I will ask about the fuel filter. The truck has been treated well and has had little real use, and less hard use. It was used to tow a minivan several years ago (2005) and has been doing this hard shifting when warm ever since. The tranny is suspect, but he is waiting til it pure pukes before changing it out. I was hoping to avoid that entirely.

Aaron

Allan in NE · May 2, 2011

Check the oil in the morning cold before ya work 'er hard. It isn't overfull is it?

If that vent is plugged, when you open up that dipstick like that it will absolutey puke oil everywhere when hot because the transmission can't breathe.

If that fuel filter doesn't fix the problem, I'd sure drop the pan and see what's lying in the bottom.

Allan

Aaron Ford · May 2, 2011

No fluid puking, but I will check the level when cold. The last comment made me chuckle!

Thanks Allan (and others)

Aaron

buickanddeere · May 2, 2011

Hard use doesn't matter. One tank of dirty fuel from Bubba's discount gaz will plug the filter.

Allan in NE · May 3, 2011

For suue,

And that plugged filter affects the transmission long before you notice it at the engine.

Allan

tlak · May 3, 2011

Obviously a fluid and filter change with an additive is in order and may get a few more miles out of the trans. That trans wasn't made right for the long haul. Wrong gearing so it works too hard. Had a starter going out and the heat of it shorting out caused my trans to act the same.

David G · May 3, 2011

I would agree with the others on checking the vent. You need to keep that fluid changed every 50K on a GM. It is not good if the fluid smells burnt. The Allison's recommend changing it 25K on severe duty.

barnE · May 3, 2011

Had Chrysler year ago. Would blow fluid out when towing trailer. Found out AC was on even when turned off. Pulled clutch wire when towing, problem gone. Dave

barnE · May 3, 2011

Make that years ago. Like 1974

woopdedo · May 14, 2011

Arron, Give me a call again about the chevy truck and my old F-40 hyd pump..
(still haven't gotten it fixed correctly. LONG story)
901-270-5295 Errol from Mississippi

Remember me?

96 Chevrolet Transmission Pressurizing

Aaron Ford

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Allan in NE

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