Ok, I had to replace my stock transmission this week. My old one had been slipping pretty baddly for some time, and finally, last week, my flex plate blew. So, the new tranny and torque converter were installed today. It's an after market 4L60E with a new stock converter. The new tranny is a better, street/strip version. I had my mechanic install it, but when I picked it up, something just didn't seem right. It was slipping, but not like the old one was. It only slips under mod/heavy acceleration, and kind of jumps, studders and just lacks that LS1 power. The mechanic told me that it may just be because that the tranny needs to be "broke in". Under regular driving, it seems fine, with nice crisp hard sifts. Here's one thing that I know, he put regular dextron fluid in it. Should I have trick shift or red line fluid running in it insted, or maybe an additive? Would this be a symtom of the wrong fluid in it? Or, like I posted in the "Exhaust" forum, could this be my CAT? Any suggestions?

 

Did they replace that electical thing on the side of the trans,or use your old one?Hope some trans folks chime in here.Hope this helps.

 

We use regular Dexron 3 / Mercon in EVERYTHING! Special fluid isn't needed. I'd take the transmission back to whoever built it. It sounds like it's losing pressure at higher RPM's. Is this person a reputable 4L60E builder? Your "mechanic" is full of crap. An automatic transmission doesn't need any "break in time".

My suggestion would be to have the person who built it take care of it. You can check the pressure with a guage yourself. The line pressure tap in just above the linkage. If it's dropping pressure with more throttle opening, then you may have a pressure control solenoid or pump problem.

Frank
CPT