Transmission slam at 45-50 MPH?

[Fire & Ice]

Hey guys, I'm hoping you can help me diagnose this from afar. My '99 Yukon 5.7 liter seems to be having an auto trans issue. As I get to about 45-50 mph (normal/conservative driving) there seems to be a hard shift like it's banging into gear. Sometimes it seems like it goes in OK then quickly out and in again hard. I'm wondering if this is the point where the torque converter locks up and if this could be the culprit. I just recently had the ATF changed and "flushed" and the trans filter changed. The fluid looks and smells good and is at the proper level. Any help would be appreciated. Thanks!!!

 

[GMCYukalade]

Might have should have not have done the fluid flush - but yes it does kinda sound like the TC is the culprit - you know the TC out of the S-10 4.3 l fits in our trucks, and is a better built TC

 

[Fire & Ice]

To GMCYukalade

GMCYukalade,

Thanks for your prompt reply. Are you saying I SHOULDN'T have had the trans fluid flushed? I bought the truck 5 years ago with 58,000 miles on it. I don't know if or when the trans fluid had been changed before I bought it but it seemed OK (didn't seem burnt, etc.). I am embarrassed to tell you the next part. I only had the trans fluid changed at 92,000 miles. I just went on a long trip so now the odometer now sits at 96,000. Maybe you are saying that if the trans fluid hadn't been changed often enough I shouldn't have changed it at all? Also you mentioned the alternate TC. I am guessing that is OK for 4-wheel drive? Thanks in advance for your comments & input.

 

[GMCYukalade]

You would have to look it up - but 4x4 the 4l60e is the same up front as it is with 2x4 - and all i was saying was people have had a hard time out of trannys that were completly flushed - instead of just a regular fluid/filter change

 

[Fire & Ice]

Thanks! I appreciate the help!