Daryl Posted June 11, 2014 Share Posted June 11, 2014 Ok gents, I just installed my TCI 4l80e controller to give it a test run on my freshly rebuilt 4l80e. All gears work except for 2nd. The engine and transmission is currently in the frame and there is no driveshaft hooked up to it nor is the body on the frame. Now from what I've read the 2 most common problems that could be causing this is #1.the sprag is on backwards or #2. there is not a sufficient load to engage the sprag since the drive train is not completely hooked up and under pressure. Has anyone out there encountered this problem with a 4l80e or the th400? I mention the 400 as well as the 4l80e because from what I have read the intermediate drum setup is exactly the same for both transmissions. Can you guys think of anything else I should try before I tear into the transmission? Also do you think I hurt anything if the sprag is on backwards? like I said the trans is not under any load nor has it been since its rebuild. Quote Link to comment Share on other sites More sharing options...
wallaby Posted June 11, 2014 Share Posted June 11, 2014 Wow, from the little I know about auto trans, I'd say it's a little early to freak out. If there is ZERO load on the output side, why would the trans think 2nd is needed? I could be wrong, but the trans looks at a bunch of different criteria (road speed, engine speed, engine load, throttle opening, etc.) to determine what gear is needed to get the job done. Right now a lot of that information is missing or misleading. I'm almost surprised it shifts at all, I'd expect it to start in high gear if it thought it could get away with it. One of the things an auto trans does is internally compare the speeds of the input shaft with the speed of the output shaft. (maybe load is a better word) If they are the same or close, the trans seeks a higher gear. Another way to look at it is the trans pump makes a given pressure and it is used to move the car...if the car is resisting that movement, some of the pressure is directed to engage bands/clutches that engage lower gearsets for more leverage to get the car going. Right now the trans thinks you are cruising downhill with little/no throttle...I'm not surprised it's trying to get to high gear as quick as it can. Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted June 13, 2014 Share Posted June 13, 2014 What Mark said! Quote Link to comment Share on other sites More sharing options...
Daryl Posted June 13, 2014 Author Share Posted June 13, 2014 Ok, I'll take a chill pill and wait till I get most of the car back together. Quote Link to comment Share on other sites More sharing options...
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