Hi guys, I received alot of great help on this forum last time I had trans issues, especially from Dana at Pro Built. Now I'm having issues again and hope you can help.

For a brief recap, my 700R4 lost 3rd gear last summer. I was pretty sure after the tear down that the main culprit was hard, high rev 2-3 upshifts. I made alot of changes to the unit during the rebuild this winter, including the trango high rev spring kit, to prevent subsequent failure. Since the build, the unit has performed beautifully. Recently I've started more highway cruising in OD and letting the unit autoshift. I've noticed some sloppy part throttle downshifts from 4th to 3rd but thought it was the TCC disengaging . Now, 3rd gear is much softer than it has been and cruising in 4th the last day I drove the car, the trans lost drive and I was unable to re-engage 3rd even manually until I parked the car for a bit. The fluid, that's been fresh every time Ive checked it, smells burnt

I know that there are at least several possible causes of this issue. Any input is greatly appreciated. I plan to collect any and all parts that I may need, including a new set of 3-4 clutches, and doing the rebuild over a weekend in the next two months.

 

I'm no expert, but is it possible you can get a video next time you take it around the block? I'm curious to see what it's doing while you're driving.

 

Thanks for your reply DeltaElite121.

Perhaps I can do that. I'm an old guy and no techy for sure. I'm not driving the car right now until I redo the trans, except to diagnose it. I have all brand new parts in there including the pump and I don't want to tear up anything more. I do plan this weekend(assuming I get one of my lifts freed up) on bringing it to the shop and attaching a pressure gauge to take readings at all pressure taps in all gears to see what I can find out from that. I wish I better understood all the intricacies of this unit.

I was thinking last night about the Transgo 2-3 shift kit. I did this kit, using the full manual shifting option once before. The regular option of this kit is gear command that allows any gear at any speed, which with my high revving motor should work pretty well. I'm thinking that this kit's VB reprogram might cure any shifting issues. I was hoping though to just fix whatever has recently gone wrong rather than get radical with the Transgo kit.

One thing that was happening this last week as I felt 3rd gear get soft was a binding or dual apply shift between 2nd and 3rd. It was like the 3-4 clutch was applying before the 2-4 band was completely released. It had never done this before last week. I know that this will kill the 3-4 clutches real quick.

I will call Dana soon about some parts and to get his advice as well. One mistake that I made was using the Alto Red clutches instead of the high energy frictions he recommends. I won't make that mistake again.

 

Update: I spoke with Dana at Pro Built Automatics last Friday. He is setting up a High Energy clutch pack to fit the Smart Tech housing. Along with the new 3-4 clutches, Dana's going to set me up with a shift kit and special instructions to ensure that the 2-4 band is completely released before the 3-4 clutches engage. I thought I had that covered in my build but maybe not. I'm also getting the Sonnax 4th servo from him to increase holding power in 4th gear, and a viton input shaft/output shaft seal to replace the crummy nylon seal that came in the rebuild kit.

In addition, I got a new 4th gear pressure switch from him and I'll make sure that my TCC is working before I do anymore highway driving. Since heat played a big part in this failure, I am also going to do some upgrades on my trans cooling system to ensure cool operation on hot days.

Talking to Dana about this transmission is very reassuring. This guy knows these units like no one else I've ever spoken with. He saved me from making some poor choices and I feel so much more confident in the success of this project now having his direction. If only I had made that call last winter. I wouldn't be having to do this again. Oh well, live and learn. It will be interesting to see how things have held up over the 2Kmi since the build.