This is the second FLT 4L80e I have put in my truck in less than a year. The first one I installed, I immediately complained of a very soft 1-2 shift but my tuner told me the pressure was maxed out and couldn't be made any firmer. Here is a vid of my first 80e where you can hear how first sort of slides into second gear during WOT (40 seconds into the vid) Not long after I made that vid, trans cooked the 1-2 clutches. Shipped it back to FLT and they supposedly completely re-built me a new one and I just installed it last weekend...it's doing the exact same thing: All gears shift awesome under light throttle - less than 1/2 throttle, but as soon as you stomp on it, ONLY the 1-2 gear shifts soft. It seems like the more throttle you give it, the more it slips...but only the 1-2. The rest of the gears shift great. SO, a few days ago we hook a gauge up to the trans and do a pressure test while driving. We found 200psi during all shifts under part throttle. At WOT the 1-2 pressure drops to 180psi then back up to 200 for the 2-3 and 3-4 gears.

If anyone has ever experienced this problem and knows a solution or can offer any insight as to what may be causing this, it would be greatly appreciated. Thanks guys!

 

180 psi is high enough that slip should not be a concern.

 

If that's the case, do you know why it is slipping then...why the shift is so soft there?

 

Man I hope you get it figured out.

 

Thanks Rob, me too man! It really sucks not being able to drive it now, especially after finding out what an awesome launch this thing has during the few time I have driven it!

 

Do you know what the clearance was on the intermediate clutch pack? The steels and clutches used? The intermediates (2nd gear) are the weakest in the 80e and need to be set up extra carefully.

 

Chuck from FLT built both transmissions, I can call and find out if you know what they should be. I got an email from him the other day stating he wouldn't be in the office till Tuesday, but I'll try finding out from his other tech. and let you know. Thanks!

 

I remember seeing in the past very lazy shift times in your tune... what are they now? Could that be part of the problem?

 

A big issue is the intermediate feed bolt...it is a hollow bolt and if over-torqued can warp and leak pressure which will let the intermediates slip more. A lot of times guys will just go at it with a wrench until it feels tight (its a brass bolt) instead of a torque wrench. Not saying thats your problem, but its a possibility.

 

Just got off the phone with a tech there. He was reluctant to give out info but finally told me they use borg Warner clutches. He said Chuck was the one working on it and couldn't say what the spacing was. I'll ask him all this stuff when he gets back in the office next week though.

Thanks again for that info.