yungsurge

Ok my 99 Tahoe(4x4 4L60E) shifts fine at normal speed.But if you floor the pedal it slowly shifts from 1st to 2nd.I was thinking of changing the tranny fluid and filter but someone told me that might not be a good idea. Any one know what that can be. ****please help*****

j cAT

normally a sluggish shifting transmission is damaged fluid , low pressures, resticted dirty filter or all off the listed items...


proper maintenance of the transmission servicing depends on vehicle use and fluid condition...towing , plowing, hauling loads requires the fluid to be replaced very often...use of a large transmission cooler will aid in getting more miles on the fluid /filter servicing..



If you only use the vehicle for light duty,replacing fluid at 30-50,ooomi is recommened...

jdmccright

You don't mention the number of miles on the truck and how long it's been since the last tranny fluid change...this info helps alot.

Check the fluid level, color, and odor. It should be red, clear, and have a acrid yet slightly sweet odor (a new bottle of fluid is a good comparison). Worn out fluid is colorless to brown, sometimes opaque or milky, and can smell burned...letting the level get too low can accelerate fluid breakdown.

Changing it and the filter is a good first step. It's messy unless you undo the pan slowly. I just did this on my C2500 and it is fairly easy except for replacing the filter seal. It is a rubber-coated steel ring that is pressed into the body...TIGHT. The only way to get it out is to use a short hook to dislodge it just enough to get a screwdriver under the lip. Then carefully with a screwdriver and mallet (is that possible?) bend the seal in on itself without scratching the mating aluminum surface. Getting it dislodged is the hardest part, but if you can get under the lip right away, you're well off.

The new one goes in easily with a matched diameter deep socket, extension and mallet. I leave it just slightly unseated to give me that lip and avoid all that under-truck wrestling.

Clean the tranny pan seal faces and the square magnet. The filter kit should come with a new pan gasket. Use a thin layer of grease to help keep in position on the pan as you bolt it back together. Refill and check. Hopefully, the new fluid will help with the shifting issue.

This is not an endorsement, but I will say that with nearly 200k miles on my truck, I took a leap of faith and added some Lucas Oil Transmission Fix. It looks like very viscous transmission fluid. I was worried that if I poured it in straight it would just sit at the bottom of the pan, so I poured some into an empty tranny fluid bottle, then added regular tranny fluid and mixed it by shaking, then poured it in...I repeated this until the whole bottle was empty. So far, it has helped with smoothing out shifting but I cannot make a full assessment just yet. One bottle of Fix plus 4qts of regular fluid will fill the tranny full...but don't overfill!

Okay, this was way more than you probably wanted, but hope this helps!

__________________
Current Garage:
2003 Pontiac Vibe 1.8L AWD
2003 GMC Envoy XL (aka "fat-a$$") - K&N air filter, otherwise stock.
1995 Chevrolet C2500 2wd, 5.7L - K&N air filter, otherwise stock...my weekend hauler.
1992 Toyota Camry LE 2.2L - K&N air filter.

Vehicle History:
2004 4.7L Dakota Quad Cab 4x4
1996 GMC Jimmy 4wd
1992 Chevrolet S10 Ext. Cab 4.3L
1995 Honda ST1100...my first (and only) new vehicle.
1980 Yamaha XS400
1980 Mercury Bobcat...my first car.

yungsurge

Thanks for all the help but now the shifting isn't as bad but I'm getting a grinding noise when driving. Do you think it's the torque converter? The truck has 166k miles and I just bought it so I don't when the tranny fluid was changed last.Also the tranny fluid does look a lil brown and smells a lil burnt.

MT-2500

Grinding not good.

A good transmission capable scanner would have a lot of info in it on taransmission operation.
May have codes to.
If so post back codes.

Also pull the pan and look in the bottom for metal and cluch shaving and trash.
And remove and cut open the filter for inspection.

If pan and filter is full of trash it may be time for a transmission rebuilt or replace.
166k is high mileage on a transmission.
Let us know on codes and what is in the bottom of transmission pan.
Good Luck

__________________
Remember proper testing gives us the answer to many problems.
MT