98 GMC Sierra Transmission problums

Dustin Simms

Asked by Feb 18, 2015 at 10:57 PM about the GMC Sierra 1500

Question type: Maintenance & Repair

Hello, I have a 98 Sierra 2WD with a 5.7 in it. The truck has 72,000 miles on it. The
engine about 3,000 on a GM crate motor. About 4 days ago I started hearing a horrible
whining sound( like metal on metal) intermittently coming from the transmission area.
took it to a local trans shop and was told it sounded like a cracked flywheel. I pulled
the trans and flywheel and the flyeheel is clean(except the bolt holes seem to be a bit
wallered out. Heres the thing, the sound is there and loud when you first start the
truck. Once it warms up the noise goes away at idle and comes back when
accelerating. while driving if I let off the gas the noise stops. Where do I go from here?
Do I put a new flywheel in anyway? Is there something I need to check 1st?

7 Answers


Are you talking automatic or standard transmission?

Dustin Simms

Im sorry, automatic


Ok replace the flex plate, it should not have any mal-shaped holes, You are describing a front pump noise, it could be caused by a worn pump drive on the torque converter or even a bad pump. Did the noise raise and lower as the engine speed increased and decreased?

Dustin Simms



Ok, remove the torque converter and look at the notches in the hub and if there are any groves in it, if the notches are showing any signs of wear then the converter needs replaced, if the running surface is grooved you can repair it with a "speedy sleeve" after that you need to replace the pump and seals, it is a fairly straight forward repair replacing the pump, just make sure when you put the converter back in that it is locked into the pump all the way, if you don't get it right you will break the new pump when you bolt it back up. HTH

Dustin Simms

I'll look into it and let you know what happens. Thank you..


Sure. Good Luck and take care.

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