Hey guys got a few problems ive read on here a bit with similar issues and tried everything and it is still persistent. I swapped a 98 motor into my 96 jimmy and did plugs wires cap and rotor and coil to start out and fix my misfire issue. now when im driving in torque lock up it "shudders'' as everyone seems to be calling it. It never did this when my old motor was in. Ive changed the tranny fluid and filter and the transmission control solenoid.
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hoping that was it and isnt. when i am driving around at 70-75 it has a shudder or hesitation and no ses light. Any idea on what this could be?

 

come on guys no one knows anything about this issue?

 

Loose TC and other things may cause a shudder. Do you think it is engine misfiring or more a out of balance type of shudder?

 

Loose maybe a option never thought of that and I know its not misfiring I've ruled out everything electrical I think. It only does it about 70 75 if it kicks out it won't go back in. Ill have to take a look tomorrow thanks for the idea!

 

These 4.3's are fussy when it comes to secondary ignition parts, what brand did you use?
Have you checked fuel pressure and leakdown?
Have you checked camshaft retard?
Did you perform the crankshaft position sensor relearn? This is mandatory with an engine change. If it's not done, the PCM uses data from the old engine.

 

I used everything acdelco I heard Thats the best to use. The fuel pressure looks good according to the shop that checked the motor before I purchased it.
I haven't been able to check that nor did I think of that. How do I check the camshaft retard? Or do the crankshaft relearn?

 

AC Delco is the best, (and the only brand to use) especially in these vehicles. Far too many problems with aftermarket stuff.

Fuel pressure: Don't take their word for it; of course it "looked good" they're trying to sell you a vehicle. Most auto parts stores rent and or sell fuel pressure testers for around $40. If you're planning on keeping this vehicle for a while, it would be a good idea to invest in one.

Camshaft retard and crankshaft position sensor relearn are accessed using a capable scan tool. The el cheapo ones, ($300-$400) that the auto parts stores have, won't do it. Most any bi-directional scan tool will access both. Might be cheaper to have a qualified shop do it for you.

 

So today I went to the local shop ive been going to for the past few years they looked and said there isnt a way to make it relearn. the shop has a snap on scan tool with a big screen. they did a transmission relearn to see if that would help. the owner suggested that the throttle body from the new motor (out of a 1998) could be the issue i put the original one back in from a 1996. i accelerated down the on ramp slowly and it went into overdrive at about 50 mph and accelerated to 70-75 mph. on the free way for about 10 min kicked it in and out of overdrive a few times... No problems and went back in so i kept driving and kicked it out of overdrive again (around 70-75)and it did the shudder/hesitation. this time was not as bad as others the rpms bounced between 100 rpms difference. then got off the free way drove back to town went into overdrive no problems.
what could this be?

 

Time to find another shop that knows how to operate their scan tool! On the Snap On scan tool, it's on the "Functional tests" menu page.

 

I will tell them that tomorrow when i stop in there.

Now when i was on my way home i had my truck in drive just D on the indicator. and with light throttle it did the shudder at about 40mph and 2k rpms. then put into od and it was fine. does this help with any other ideas?