What To Do Next?

383S-10 · May 23, 2007

I think I had this in the wrong forum 1st....Im very sorry about that.......

I have 98 GMC Sierra that I recently had the sidetank replaced on the radiator. A few days later it started shudder/vibrate around 40 to 60 mph. I felt it was transmission problem so I took it to my transmission guy who test drove it twice for me in one day. Now this guy eats, sleeps, & drag races Chevys and in his pro opinion he felt it wasnt a trans problem but that it was an engine stumble/miss problem. He told me I needed to go and tune it up & check all the igntion stuff.

So heres what I did:

1. Bought new set fo Taylor wires & NGK TR-55 spark plugs; replaced same.

2. Pulled off mass air flow & cleaned same.

3. Bought new rotor & distributor cap, replaced same.

4. Bought new fuel filter, replaced same.

5. Had codes checked even though no SES light come on, only code was PO161.

6. Pulled & cleaned EGR, the pintel had carbon build up on it and moved down into EGR after

cleaning it moved further and more free than before.

Now after all this the truck ran better, more pick up, snappy response, but after 2 days it started shuddering/vibrating between 50 to 55 mph, then later it did it 50 to 60 mph, now its back to 40 to 60 mph.

I took it to another transmission shop & he said it was the torque convertor.......he said after 177,000 miles its time & well over due to rebuild the trans at a cost of $1300 plus dollars.

My original trans guy said after I run through the tune bring it back if it is still acting up.......well I did & he test drove it today. He says that the torque convertor isnt slipping to him & that I have something else wrong. He said he would be glad to rebuild it & replace the torque convertor for a price of $1050 but he really feels that not the problem & that he would taking my money if he did that.

So now Im at the cross road of decision making.....tomorrow I plan to have the fuel regulator replaced to cross off one more thing that could be the problem. I did everything on it........I dont fuel pressure gauge to check fuel pressure.... but I replaced the fuel pump a year ago in June 06. Is it easy to replace the fuel regulator on 98 5.7 Vortec? Or do you need any special tools to this? This forum board has helped so much in the past with info for my truck....I just usually do a search & found the answer I needed to fix the problem. But this time Im not so sure what to do about it.

Truck info 1998 GMC Sierra

5.7 Vortec

4L60E

177,343 miles

P.S. The truck & me tackled the 2005 HOT ROD POWER TOUR leaving N. Alabama to start in Milwaukee, WI

to the finish in Kissimmee, FL & back to N. Alabama.

Once again thanks for all the help now & in the past you have given me.

ryank1 · May 24, 2007

Did you have the side tank replaced for a leak in the trans cooler? If so I would lean towards the trans. Coolant in a trans will destroy all of the fibers and the convertor clutch.

383S-10 · May 24, 2007

Thanks for replying Ryan........I had the side take replaced on the drivers side because I had a leak on what I was told was the upper oil coiler line that leaked anti-freeze down the side tank.

RCH · May 24, 2007

I would check out the torque converter. Our Saffari van did exactly the same thing, I replaced the "U" joints and had the drive shaft balanced, but that didn't fix it. Finally took it to a transmission shop and they diagnosed the TC. Maybe when you had the radiator out something may have got in and went through the line as RyanK1 said.

Jeremy WI · May 29, 2007

I got the parts you emailed about at gmpartsdirect.com

You may want to look at your distributor gear, if the shudder only happens with light throttle and disapears if you floor it. Distributor gear is only about $25

383S-10 · May 30, 2007

Thanks for the reply guys..........now I just Seafoamed my truck at work yesterday it is running a lot stonger and the shudder is a lot less but still there. It will accelerate quickly but the shudder it happening at about 50 mph to 60 mph for a short time. I read some stuff on the spider injector on my truck another local mechanics thinks thats the problem but he has misdiagnosed a few these by trying check the fuel pressure when it turned out to be bad fuel pumps. Ihave already replaced 2 fuel pumps in the last 2 years on my truck. The 1st replaced lasted 1 year to the week of replacing it......it took some convincing but Oreillys game me another for it for free.

So now I got run out this half can of seafoam in my tank to complete this leg the test. Can anyone suggest somewhere I can get the timing checked after I change out the distributor gear.....the guy I asked to do the spider injection swap said I need to go to the dealership but I see where some people use what I think is a hand held snap on unit.........I dont know anyone who has one in the Alabama woods........we have huge, huge hogs.......but no snap on hand helds....lol.....Thanks everyone.