Cold Weather auto tranny shifting

c4cruiser · January 14, 2005

I have noticed lately when the air temps drop 8-10 degrees below freezing that my 99 Silverado Z71 seems to take longer to upshift in the first few miles of running.

This morning the outside temps were about 25 and in the first couple miles of driving at 25 to 35 on residential streets, the tranny didn't want to shift into 3rd below about 35 and it wouldn't shift into OD until I hit almost 40. I could force a shift into OD by going faster but as soon as speed dropped below about 36, the tranny would drop back to 3rd. Moving the shift lever between 3rd and OD made no difference.

Water temps at this point were from initial start-up to about 150-170 degrees. The 1-2 upshift seems normal and is firm.

The truck has just under 50K on it and the tranny otherwises shifts fine and all the shifts are firm. I don't tow anything or shift manually. It almost feels like the tow/hual mode is activated.

Any ideas/comments??

99GMCZ71 · January 14, 2005

The transmisson has a temp sensor in it that does stop the convertor from locking up until the transmission reaches a certain temp. It may also affect the shifting. Plus it will shift different when the fluid is cold.

2000 GMC · January 14, 2005

I just happened to log on to ask this same question. I've noticed this also since moving to Colorado.

99silveradoz71 · January 15, 2005

I had a feeling from reading your title that I'd be typing the "it's normal", and so I do. My Rado does the same.

biochemist · January 15, 2005

Mine too...seems to shift a little harder from 1-2 when warming up (live in Mass), also depends on what speed the truck is going (how far my foot pushes down) it will shift real smooth or a little firmer, when putting around seems to shift harder than when taking off normally. Seems a little touchy and really depends on how I drive but I guess the cold weather and the fact the transmission is always 'learning' will lead to this, but acted this way since new....hope this helps.

snarkee · January 15, 2005

when its cold mine holds the gear longer and the engine sounds different....kinda like air rushin thru it

but its normal

04 z71

ness5575 · January 15, 2005

mine does the same thing! so does my gf''s envoy, just had it out (its like -2 here) and it shifted the same as mine does when its cold!

sjspor · January 15, 2005

That's normal, the PCM holds the shifts longer to warm the truck faster. It's actually supposed to do it.

biochemist · January 15, 2005

So, they are supposed to hold shifts longer when cold...and the character of the shift changes too? As I said, mine seems to shift a little harder when cold (just 1-2 though). Dealers say normal..... what do you guys say, sounds normal and I guess some people prefer harder firmer shifts anyway? Thanks

budhayes3 · January 15, 2005

Yep, that's normal. Even on non electronically controlled transmissions, the shift characteristics will be different when cold due to the physical properties of the trans fluid at different temperatures. Combine that with the PCM logic, and you will feel a difference until the vehicle warms up.

biochemist · January 15, 2005

c4crusier..did not mean to push you out but I posted a similar question....but as I said earlier, I think this is normal... I have an 04 with a shift issue when cold also and wanted to explain what I notice...this is a great forum for these types of questions

Bish · January 15, 2005

One big reason they shift that way when cold is to speed warmup time. May even be CAFE related as faster warmup leads to less pollution and better mpg.

RyanZ71 · January 16, 2005

if I let my silverado warm up for about 3-5 min before driving it I never have any problems with it shifting however if I do a cold start and drive immediatly it will shift like you describe. Try letting it warm up for 2-3 min (until the idle drops down to normal) and then drive. Saves wear and tear on your engine and tranny.

slaterx2 · January 17, 2005

Yes, I'm convinced it's all about the fluid and the e-controlled drivetrain. We have had the standard farmin%$k&^g winter freezing arse cold here (-40c = - 40f... right?) . I have been plugging in and burning alot of fuel warming up before driving (15 min +). I understand that recommended practice is to set the "PARK" brake and put the trans in neutral in order to warm it during exteme conditions. I dont trust my 'emergency' (formerly known as) brake though. Truck goes 20 miles+ to work at these low (outside) conditions and crappy roads with normal engine temp, but the transmission shifts like it's in tow/haul mode the whole way. I don't think it warms up. I kind of wish i had a shut/cutoff valve for the tranny cooler; just for these conditions.

c4cruiser · January 19, 2005

Was reading an AC Delco tech newsletter at out shop yesteday and there was an article reagarding this problem. The article said that the shift solenoids may be the problem and delayed shifting due to cold temps can happen in any upshift pattern (1-2, 2-3, or 3-4 or all of them). But the issue was tranny specific.

And of course, I can't remember the specific tranny model mentioned in the article right now (another case of CRS ). What tranny is in the truck I have?? 5.3L motor, Z71 1/2 ton ex-cab. A variant of the 4L60E??