98 tahoe 5.7 4x4 shifting hard

[dp81]

my 98 tahoe 5.7 4x4 shifts hard (1st and 2nd gear) after a long drive.i shut it off and keep going and a few min. late it does it again???????

[jdmccright]

First check the transmission fluid level and condition. If it is low try to refill it. If it looks clear or brownish, or smells burned, it's time to change it.

Most people in here will recommend that you NOT flush the transmission, especially after running it wayyyy past a scheduled change. But most drain & fill changes only change about 1/2 the fluid. In your case, I'd remove the pan as well so you can change the filter inside as well as clean off the particulate magnet on the inside of the pan.

If you're a DIYer, (and presuming you have the 4L60E transmission) the o-ring seal for the new filter is a PITA to remove if it has been driven all the way into the valve body. I've had luck with using one of the jaws of a pulley puller as a big hook with a screwdriver slid through one of the holes as a handle to grip with both hands. Make sure the truck is securely on jack stands and wheels chock-blocked...and pull down with all your might. At minimum you'll dislodge it enough to be able to collapse it with a screwdriver and hammer. Once removed, drive the new one in with a socket but leave the lip of it slightly extended below the valve body's hole so that you can remove it by collapsing it...without all the massive yanking. If it doesn't have one, think about installing a drain plug in the pan.

Reinstall the filter, pan, and refill. Run it for a few hundred miles, then drain & refill again. Run another few hundred and drain & refill again. Yes, it sounds bothersome and wasteful, but the deposits that have built-up inside the valves and passages are slowly dissolved this way, rather than them breaking off during a high-pressure flush and causing a blockage more critical elsewhere. Two changes is good, three is better.

If the symptoms still exist, an option after the last drain is to substitute some tranny additive like Lucas Transmission Fix to help stop internal leaks and smooth out rough shifts. Use as directed on bottle...DO NOT OVERFILL.

If your truck doesn't have an external transmission cooler (usually included with the trailering option package), I'd seriously recommend one...especially if you live in a hot climate. Heat kills trannys and the lines going to/from your radiator only cool it down to the coolant's temp of ~200°F. A second cooler in line with the return hose from the radiator will let you cool it further, giving your tranny a little extra relief.

Hope all this helps!