97' Tahoe Jerking ... Help!

97 Tahoe - Jerks - Plz Help!

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Hiya!

I'm new to this forum, my first post.  My reason for posting is as follows:

My husband and I have a 97' Tahoe with 180,000 miles.  After having the transmission rebuilt = Twice in less than a month, the engine blew.  We had a local mechanic rebuild the engine.  Parts were fine, everything looked great.  On the first drive home, it jerked once.  Asked mechanic about it, told possible timing high and sitting for awhile, should stop.  Well, it didn't.  It has consistantly gotten worse.  It began doing it in OverDrive, but it started jerking in 3rd also.  I have yet to try 4X4. 

The mechanic has NO answer.  Nothing he did.  The transmission guy has no answer, nothing he did.  A seperate shop has no answer except its not the transmission, they couldn't put it on the inshop diagnostic because it only does it driving.  Took it out driving, wasn't consistent enough for an answer.  Was told , will be able to tell when it stops.  I said, "when the jerking stops?", he said "No, when the truck completely stops running".    What kind of answer is that?


I am so aggrevated that noone seems to have a clue as to why an engine would jerk hard like this.  I've had cars/trucks jerk hard when the sparkplugs weren't connecting.  Transmission problems jerked it before but it isn't the same thing.  Doesn't feel like the trans. and it doens't jerk right on top of eachother like the trany did.  It can jerk and not jerk for 5 minutes down the road or 2 minutes. 

Oh, and it also hesitates when taking off.  Not all the time, but most.  Feels sometimes like it about dies causing an 'almost lerching' feeling.  Dunno if this is part of the same problem.  My major concern is the jerks. 

Anyone have any idea?

Jerks  35mph - 75mph(fastest I've had it since rebuild)

Their is no RPM movement/flux when it does this other than normal driving
Their is no specific speed when it does this
Jerks hard... (if you hadn't felt it before you'd swear you just locked up something and it fell off) lol


I hope I have given you enough info, if not... just tell me.  I would greatly appreciate any thoughts on this mess!

Thank you!

KitaKaT
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Why was the tranny rebuilt twice?
Also, when you say the motor was rebuilt, was it completely rebuilt? ie, torn down to the block, pistons removed, crankshaft removed. etc etc?

1st Tranny rebuilt = sungear broke, decided to rebuild instead of fixing one problem
 
around 50 miles later, bearing came out in tranny, technically not a rebuild but fixed
 
Motor = Tore completely down, block dipped, line bore, bored 30 over, new freeze plugs, crank shaft machined, new gasket and bearing kit, new oil pump, cam, cam bearings, roller lifters, timing chain and gears, 30 over pistons with rings, heads machined with replacement of bad parts, new timing chain cover, new OEM sparkplugs, sparkplug wires, rotor and distribitor cap, belts and hoses. 
 
No other electronics were replaced.
 
Both block and heads were machined and dipped to insure clean oil and water passageways.
 
Oil pump primed before first start.
 
 
 
 
 

how long did you drive it after having the tranny fixed the 2nd time? was the jerking at all noticeable during this time? If not, I would tend to think it is related to the engine rebuild

I think it was around 3 weeks(not sure, hubby isn't here to verify at moment)... no jerking like this was present before the rebuild. 
 
 

sounds like it is definately related. May not be the rebuild itself, but something that was put back on wrong. If you can be without your vehicle for a few days, leave it with the shop who rebuilt the motor and tell them to drive it and figure it out. Hopefully they don't give the "It must be a coincidence that it happened right after the rebuild" excuse

Thanks, I appreciate it :)

Hmm...what about the diff? Has it been checked?
Has it been tuned since the modifications to the motor?
Was the new cam that was installed 'stock'?

I still think tranny, the jerking is in high gears, the speed won't matter as much as engine load when it's trying to hold a gear. Are you sure he put in an electronic tranny and not a vacum type?