Shimmy

I'm posting this for a friend so don't blast me too hard if it's a duplicate since I own a dodge and don't follow this group. Si
Need help identifying problem. 1998 z71, ext cab, k1500, 5.7L, auto
trans., 90K miles. A shimmy/vibration problem causing a washboard effect has developed while driving it in 2WD mode. This ONLY occurs when the drive train is under stress/torque (for example: cruise set and truck is climbing a long incline). Symptoms do not occur under other conditions, such as quick acceleration, passing gear, flat road, etc. Tires are relatively new (15K miles), have been rebalanced and rotated. I have replaced both u joints in the rear drive shaft but problem still occurs. Motor mounts and transmission brackets appear to be intact. Motor performance appears to be fine and does not miss while being revved up to high rpm's in neutral. Drive shaft is one piece. Any tips would be appreciated................Popsgunter
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When's the last time he tuned it up?
Doc
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Last tuneup was between 55 and 60K miles ago. Si
"Doc" wrote:

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. . ==== ==== Oct 24, 2004, 2:29pm (CDT+5) From: snipped-for-privacy@mindspring.com (S.A.King) wrote: Need help identifying problem.
<VEHICAL>
1998 z71, ext cab, k1500, 5.7L, auto trans., 90K miles.
<SYMPTOM>
A shimmy/vibration problem causing a washboard effect has developed while driving it in 2WD mode.
<SYMPTOM CONDITIONS>
This ONLY occurs when the drive train is under stress/torque (for example: cruise set and truck is climbing a long incline).
<PRELIMINARY DIAGNOSTICS>
Symptoms do not occur under other conditions, such as quick acceleration, passing gear, flat road, etc.
Tires are relatively new (15K miles), have been rebalanced and rotated.
I have replaced both u joints in the rear drive shaft but problem still occurs.
Motor mounts and transmission brackets appear to be intact.
Motor performance appears to be fine and does not miss while being revved up to high rpm's in neutral.
Drive shaft is one piece.
<PLEA FOR HELP>
Any tips would be appreciated................ Popsgunter ======== ========
Pops, take it out for a drive and get the symptom to start up. Then....while the washboarding is happening, lightly hold yer foot on the brake pedal while maintaining the same speed.
See if that gits rid of the washboard, shudder symptom.
The symptom is "most likely" caused by either the transmission torque convertor or an ignition breakdown being amplyfied by the torque convertor locking up. By putting yer foot on the brake pedal lightly, yer telling the computer to "unlock" the torque convertor. You should see a slight engine RPM rise when the convertor unlocks. If the symptom goes away during this test, I would tell your friend to get a reputable "TRANSMISSION" shop to do a check of the transmission. Most shops offer this as a free service.
A good shop that suspects the convertor to be causing the shudder/washboard symptom, will advise that you do a service on the tranny and add a bottle of LubeGard and a tube of Dr.Tranny ShudderFix to the fluid. The symptom the truck has is WELL documented and the above proceedure is known to solve the entire problem.
You may see this thread lengthen into a blaze of flames over the products I've suggested and to their reliability as a cure for the symptom, make up yer own mind to what you want to do. I would suggest you call a hundred "tranny" shops and ask THEM....then call a hundred DIY'ers and make yer mind up.....lmao.
a site for you......
International Lubricants, Incorporated Address:http://www.lubegard.com/
keep in mind...it could be an ignition breakdown being accentuated by the convertor on lockup, so be sure the engine is in top running shape first. A quick hookup on a scope will tell you that in a matter of seconds.
~:~ MarshMonster ~wonders if yer buddy had his transmission flushed recently~
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