Transmission shifting issue

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I have a 2003 GMC Envoy with the 4.2L inline 6 that I got about three months ago. It has 109k miles on it. I noticed that it was shifting hard when going from 1st to 2nd gear when the vehicle was cold. It seemed to be shifting at a normal point as far as RPM, just shifting hard. Last week I changed out the fluid (the old fluid wasn't that bad) to Castrol synthetic. It helped some, but this cold shifting is still an issue.

Before doing the fluid exchange I tried Lubegard red. It didn't do anything. Now, I'm not sure whether to leave things alone, or try LG red again, or Lucas Transmission Fix. The Lucas is thick, but I don't want to screw something up. At worst the LG will just not do anything.

Another note: today it was 32 degrees (F) outside. I let the vehicle warm up about 30 seconds as I normally do, and it seemed to shift fine once I started to drive even though the vehicle wasn't warm yet. So I don't know if maybe the synthetic fluid is having more of an effect due to the cold, or if it is just taking it a while to start helping more?

Just not sure what to do, re: LG red, Lucas, or leave it be?
 
When you said you changed it out, was it a pan drop and refill or did you do a complete drain/flush/refill? If pan drop and refill, there's still a good bit of old fluid still in there, another pan drop/refill or two should see the problem go away.

You don't need Lubegard, you said yourself it didn't do anything. No need for that lucas [censored] either. Trans only has 109k on it, fresh fluid alone should get it to where it should be. (Unless there's a mechanical issue, in which case the other snake oils won't help either)
 
Originally Posted By: wallyuwl

Another note: today it was 32 degrees (F) outside. I let the vehicle warm up about 30 seconds as I normally do, and it seemed to shift fine once I started to drive even though the vehicle wasn't warm yet. So I don't know if maybe the synthetic fluid is having more of an effect due to the cold, or if it is just taking it a while to start helping more?

Just not sure what to do, re: LG red, Lucas, or leave it be?



On a vehicle that old with that amount of mileage, just let it idle for 30 seconds to a minute before driving on a cold start in cold weather. I'd probably wait 15-30 seconds before engaging the transmission on a warm start too. I do, but my transmission was made in 1995 and has 242K miles on it.
 
I had this same thing with my 2005 Envoy. I have 98,000 miles and its a firm shift from 1 to 2 when cold. I had a friend recommend LiquiMoly ATF Additive when my Chrysler trans was acting up. I put the LiquiMoly in the Chrysler and its been perfect, no problems for the last 10,000 miles. That car is at 140K on the original transmission. I did the same with the Envoy, put in the LiquiMoly ATF Additive, once that works itself through the transmission, I no longer have that problem after about 3-4 days. Shifts smoother, I can still feel the 1-2 shift but its nothing at all like it was before, the other shifts are seamless. I have the original transmission fluid in it, was still real clean so I am going to follow the manual and change it at 100K in the spring.
 
Originally Posted By: Kuato
When you said you changed it out, was it a pan drop and refill or did you do a complete drain/flush/refill? If pan drop and refill, there's still a good bit of old fluid still in there, another pan drop/refill or two should see the problem go away.

You don't need Lubegard, you said yourself it didn't do anything. No need for that lucas [censored] either. Trans only has 109k on it, fresh fluid alone should get it to where it should be. (Unless there's a mechanical issue, in which case the other snake oils won't help either)


It was an exchange using the method of disconnecting the cooler line. So I bet I got it about 90% or more new fluid.

Might try the Liqui Moly. I know several years ago it was all the rage one here.

Any other thoughts appreciated.
 
My 02 Envoy with 200K+ did that, never any other tranny issues. Apparently the tranny had been rebuilt/replaced at 100K so tranny only had a bit over 100K on it.
 
IIRC back in the day when I owned my 2005 Trailblazer 4x4 and participated on GM T360 forums, there is a 1-2 shift accumulator piston for the 4L60E, under the pan next to the valve body that can wear and cause a delayed 1-2 shift and/or a bang into 2nd. I guess experimenting with different viscosity ATFs can mask it.
 
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Slow shifts on GMs usually means sticking shift valves, etc. Adding a thickener makes it worse.

SeaFoam's Trans Tune, thins it out, which speeds up slow shifts. I've used on GM 4T65Es for 4 years
now with good results, so I keep some in stock and buy more as it comes on sale.

When you drop the pan, see if there's more space in the pan for magnets to pick up
wear metals that score and gall valves in the valve body and solenoids. GM puts in
cheapest magnets they can get away with or worse!

Note the fit of the oil pan with extra magnets against parts that hang low off the tranny,
many GM tranny pans are "zero clearance" where the oil filter almost sits on the bottom of the pan,
with some experimentation, you can find spots on the pan that don't interfere to place
more magnets - something GM skimps on!

Using an additive to thicken AFT works when you start off with shudder, etc due to
leaking short lip seals, input clutch, etc.
 
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