2000 GMC trans question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Boog** · 02-21-2010, 02:10 PM

2000 GMC
5.3 auto
Z71
133,000 miles

I've been noticing on the first startup of the day on these cold mornings, below 30* there seems to be a delayed upshift until the engine temp reaches 180 or so. The 1-2 shift runs normally but the 2-3 shift doesn't happen until 35 mph. Then the c lockup not until 45 mph. Once the temp gets up to 180 it shifts normally in all gears. On days when this occurs it is usually only when leaving the house first thing in the morning. The rest of the day it shifts normally even if ambient temp is below 30 and the truck has cooled off.
Is this by chance a warmup feature of these trucks or is it maybe a pressure problem developing?

02-21-2010, 02:10 PM	#1
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,513	2000 GMC trans question 2000 GMC 5.3 auto Z71 133,000 miles I've been noticing on the first startup of the day on these cold mornings, below 30* there seems to be a delayed upshift until the engine temp reaches 180 or so. The 1-2 shift runs normally but the 2-3 shift doesn't happen until 35 mph. Then the c lockup not until 45 mph. Once the temp gets up to 180 it shifts normally in all gears. On days when this occurs it is usually only when leaving the house first thing in the morning. The rest of the day it shifts normally even if ambient temp is below 30 and the truck has cooled off. Is this by chance a warmup feature of these trucks or is it maybe a pressure problem developing? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross



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