If I understand TC lock-up correctly, lock-up is determined by the tune. Correct?

Next, are there different TC's with different stall speeds available for the 4R100?

Since I am going to have the TC and Tran out of the truck, should I go ahead and replace the rear main seal?

 

The conventional wisdom on the rear seal is this....if it isn't leaking, leave it alone.

The TC from a 5R110 has a different stall (I seem to recall) than that of the stock 4R100. When I ordered my trans from DieselSite, I ordered the 5R110 TC.

 

Thank you for the info. Do you happen to recall the stall speed? Is it lower? If not, since you tow heavy, do you think it is helpful for heavy loads?

 

As I recall, the 5R110 has a lower stall. Swamps, however, preferred a higher stall, allowing the engine to be more in the powerband.

 

Yes, you can get different stall speeds in the 4R100. It is one of the more overlooked details when buying a torque converter from what I have seen and heard. I got mine with the stall speed set at 1900. You can get them customized lower and higher from places that sell racing TCs or from a company like Precision of New Hampton. PoNH told me they could customize to any stall speed I wanted (within reason of course) for a few extra bills. I bought one of their pre-made DIESEL products at the 1900 setting. I absolutely love it after driving for so long with the CRAP TC Ford put in there. Major, major difference.

Your optimal stall speed depends on the power band of your engine. Gotta know that first. The 7.3 enters its power band around 1700 RPMs, and comes out around 2600 (on a "normal" truck).

 

Ford set the stock TC stall on our diesel trucks at 2300 RPMs. Absolutely ridiculous...

http://bankspower.com/techarticles/s...ng-Stall-Speed

http://www.gopnh.com/Ford-Heavy-Duty...Converters.cfm

If you check this thread, there is some very good info about TCs starting on page 3 post #34 https://www.ford-trucks.com/forums/1...er-255k-3.html

 

Wow! Thank you for those links and all of the research you did. I don't know how I missed this while searching. All of that will be very helpful for making the decision on the stall speed for the TC.

 

I would really like to feel a 1600 stall speed. If I had to do it over again, I would likely go with the 2648APSRV-MAX (1600RPM) instead of the 2648APSRV (1900RPM) from PoNH. I don't tow that much, but I would like to feel how it drives.