TH400 Transmission question

[76chev454]

Not sure which forum to post this, so here goes.  The TH400 in my 496CID C10 76 Stepside had to be rebuilt.  Rear gears are 3.43:1.  It was giving a slight "shudder" when shifting between 2nd and 3rd.  Had shift kit installed.  Using Mobil One tranny fluid.  Well, it is still "shuddering" some between shifts.  Mechanic will not take any money for rebuild until he figures out that problem.  How's that for honesty?  Really a great shop and very patient with hp trucks and cars.  Does anyone have a suggestion what my problem might be?  I have searched forum but did not find many topics relating to transmission problems.  After comment, the u-joints were also replaced along with the driveshaft center coupler.  Help! Thanks.

Professor of Interesting Stuff!

[Blazin]

Did he replace the torque converter? A buddy of mine does transmisions, he had a customer that insitsted that the torque converter had been replaced about six months before he had him rebuild the trans. He wouldn't let him buy a new converter which he always does when rebuilding a trans. This was a TH350 in a K10 and it shuddered from gear to gear. Suposedly the guy replaced the coverter with a new one due to a vibration, somehow he surmised that a wieght had fallen off the converter. He complianed that it shuddered between gears. Well after the rebuild it still shuddered. He wouldn't pay my buddy etc. etc. My budy was convinced it was the converter. I ended up talking them into letting him take it out and replace the converter with a brand new one I had just bought for my TH350 in my truck. Guess what problem solved. He payed my buddy and bought me another converter.

[76chev454]

Yes, a new converter was installed.  Glad you asked though.  Thanks for reply.

Professor of Interesting Stuff!