another thought is that something is sending a signal to the convertor to lock in reverse, after all it was doing it with the old tranny for years, not all the time but at least 1 out of 5 times.

 

Have you ever looked at a torque converter? It's not electronic. It's an rpm controlled mechanical object. No wires going to a torque converter to send it a signal.

 

Also, if you paid a shop to install a new torque converter, you should have a parts and labor warranty unless you used a fly by night shade tree mechanic. If that's the case, maybe you can spend the money you initially saved on a better converter and another case of beer for Billy Bob. Not being a dick, but I've been there, done that! If you start right now, break long enough to watch Talladega, you can have the tranny unbolted and slid back on a jack and have the converter swapped by bed time.

 

no, 1 & 1/2 year warranty.

 

Okay, I think you said that you just installed the trans and converter about a month ago and you have an 18 month warranty for parts and labor, which to be honest, is better than most places around here. Usually we get a 12 month, 12k mile warranty. This is what I'd do....Google the issue.....dying in reverse...print off a handful of ford truck related issues, be prepared to argue. If the shop wants to argue, let them know that you've done your homework and they should have too. Pull out your search results to show them that this is a common problem and they should have used the highest quality converter and trans parts or they should have been prepared to deal with the follow up repair. You do realize that you may have been charged for a new converter and did not get one, right? New trans, old converter, compounded problem! If the shop still wants to argue, make sure that your written warranty covers both parts and labors. If it does, let them know, if it comes down to that point, that your prepared to contact the Better Business Bureau and or a lawyer. I'm sure you already looked them up on the BBB Web site before you used them since 90% of transmission shops are fly by night and have numerous BBB complaints. I've dealt with the unfortunate situation of being stupid and using a shop before I looked them up only to find pages upon pages of unresolved BBB complaints. Cost me about $3k for my last trans after the third rebuild only to find out that my radiator trans lines had corroded and blocked up. The shop said that they don't do cooling, they do transmissions! Oh and by the way, the BBB sided with the transmission shop because, according to the shop, they service transmissions, not radiators.....F'n idiots!

 

checked the TPS and its right on for voltage and resistance.

 

The converter itself ain't electronic, but it's internal lockup clutch IS controlled electronically. Inside the transmission near the valve body is a converter clutch solenoid which controls clutch application by providing hydraulic pressure to the clutch apply piston INSIDE the torque converter.