Occasional transmission slip from complete stop

[clandr1]

Hi everyone,
I've been dealing with this issue for about the last 30,000 miles or so. It started after a fluid and filter change around 195,000 miles.

On occasion, the transmission will hesitate/slip when I begin to apply gas to start moving after coming to a complete stop at an intersection. It typically only happens at stop signs where there is a brief stop/start. When I sit at a red light, it typically is not an issue.

I wonder if there's a problem where my transmission isn't fully downshifting into 1st gear as I'm slowing down? Outside of this specific issue, the transmission shifts beautifully and works well, and is original (not rebuilt). I've taken care of it and with the exception of a dealer flush at ~30,000 miles, I've only ever done filter and fluid changes in my garage.

I should also add that on occasion it seems like when I floor the gas pedal on the highway, it takes a little longer than it should for the transmission to downshift. It's almost like the motor and transmission don't know I've floored it for about 2 seconds.

Is there a solenoid that could be going bad and in need of replacement? I've seen reference that a bad throttle position sensor could cause some of this, but given this issue started around the time I changed the transmission fluid and filter, I'm inclined to think it is not the TPS.

Thanks in advance for any input or suggestions.

 

[Mudsport96]

Everything you describe makes me think tps. But, there is always the possibility it is trans related. What year is the rig? Drive by wire or cable?

 

[clandr1]

Everything you describe makes me think tps. But, there is always the possibility it is trans related. What year is the rig? Drive by wire or cable?

Sorry, I thought my rig info was in my signature. It is a 2005 SLT 5.3L Flex Fuel. Based on a YouTube video I just watched, I believe my TPS is drive by wire.

 

[Tonyrodz]

Sorry, I thought my rig info was in my signature. It is a 2005 SLT 5.3L Flex Fuel. Based on a YouTube video I just watched, I believe my TPS is drive by wire.

ins?, 03 up is dbw.

 

[clandr1]

ins?, 03 up is dbw.

Sorry Tony, what do you mean by "ins?" Thanks for confirming my TPS is DBW.

 

[clandr1]

Bump for the weekend crew

 

[afpj]

you likely checked already, but fluid level good? Consider changing the fluid, again. While you have the pan off, check the filter, check the magnets. Main reason is if this started after your last fluid change, recheck whatever was done right before symptoms started. Just saying. What fluid did you use?

Btw, I don't think there's a weekend crew. This forum typically has much less traffic on the weekends.

 

[clandr1]

Yes, fluid level is good, I've changed the fluid and filter twice since then, and nothing out of the ordinary was in the pan or on the magnet. I used Delco transmission fluid that matched the spec for the transmission, and a Delco filter/gasket kit. I'm completely at a loss for what happened. Maybe the transmission was old enough that it just didn't like the new fluid for some reason?

 

[Mudsport96]

Hell, being drive by wire, the pedal could be going bad and sending the wrong signals.

 

[Tonyrodz]

Hell, being drive by wire, the pedal could be going bad and sending the wrong signals.

How would you know? Similar code you'd get with the reduced engine power issue?

 

[Mudsport96]

Yeah i guess youre right. If the pedal was wigging out it should throw a code.

 

[rockola1971]

Fluid change on a 195k tranny caused internal seals to swell. One is leaking and eventually it will throw its guts up on you. There is no good "tranny slip". When it slips it is the clutches slipping and overheating the fluid. Be prepared for a Rebuild.

 

[Tonyrodz]

Fluid change on a 195k tranny caused internal seals to swell. One is leaking and eventually it will throw its guts up on you. There is no good "tranny slip". When it slips it is the clutches slipping and overheating the fluid. Be prepared for a Rebuild.

In a situation like that should he just have left the trans alone? Just leave the old fluid in--no fluid change?

 

[Mudsport96]

I should also add that on occasion it seems like when I floor the gas pedal on the highway, it takes a little longer than it should for the transmission to downshift. It's almost like the motor and transmission don't know I've floored it for about 2 seconds.

Does the engine rev up when this happens and it just doesn't downshift and start moving? Or you floorboard it and just nothing?

 

[clandr1]

Does the engine rev up when this happens and it just doesn't downshift and start moving? Or you floorboard it and just nothing?

The latter - I floor it and nothing at all happens for 1-2 seconds. The transmission is not slipping in that scenario.

 

[rockola1971]

In a situation like that should he just have left the trans alone? Just leave the old fluid in--no fluid change?

At the most a pan and filter change with a transmission with that high of mileage. The 4L60E tends to throwup around 125k but i have heard of many that make it well past that before dying. Its possible the OP's tranny has never been serviced or rebuilt. My basic rule only applies to personal truck/suv (one that is not used to haul for a living, pull a boat/trailer/camper often or plowing, etc.). If truck/suv is new then leave fluid alone until 100k unless there are aggravating factors like lots of towing, mountain driving, etc. At 100k mark maybe go ahead and do a complete flush. But once much past that 100k mark then just a pan and filter change and even then its a gamble. I dont know the science behind the new fluid and the old seals but ive seen it many times over. The seals swell after too much of the fluid is changed on a high mile tranny. And once one of those seals gets leaking then its up to the tranny gods as to what fails....but make no mistake, it will be fatal to the tranny.

 

[rockola1971]

The latter - I floor it and nothing at all happens for 1-2 seconds. The transmission is not slipping in that scenario.

Its possible you have a sticking valve. How do you know the tranny is not slipping? Is the fluid pink, orange or brown? Does it smell burnt?

 

[Mudsport96]

The latter - I floor it and nothing at all happens for 1-2 seconds. The transmission is not slipping in that scenario.

This is odd. This seems like the pedal signal is getting lost somewhere. Have you scanned for codes? Do you have an app like Torque or OBDLink to watch things like tps position?

 

[clandr1]

At the most a pan and filter change with a transmission with that high of mileage. The 4L60E tends to throwup around 125k but i have heard of many that make it well past that before dying. Its possible the OP's tranny has never been serviced or rebuilt.

I've taken care of it and with the exception of a dealer flush at ~30,000 miles, I've only ever done filter and fluid changes in my garage. It is the original unit and has never been rebuilt.

 

[clandr1]

This is odd. This seems like the pedal signal is getting lost somewhere. Have you scanned for codes? Do you have an app like Torque or OBDLink to watch things like tps position?

I have scanned it and found no codes present. I have a very inexpensive code reader (link below) and will have to look and see if it is capable of reading the TPS position.

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