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Help with a 4r100

Hey all, I have a question. What would cause my van to just stop when going in reverse? It feels like the brake is on but it is not as I have checked them to verify they were not stuck on. Any thoughts? Should mention it is a 98 E 350 with the Triton V-10 and 4R100 trans. Thanks
Here is an even better question, I see all these codes like F8UP-LC, F8UP-JA,: F7UZ-VARM, F7UZ-MRM, F7UP-VA, F7UP-MA What do these mean and can someone tell me what the heck the difference is? Is that the shift module code, gear size, initials of the guy who designed it...........what????? LOL Would like to educate myself on this matter. Thanks.


Staff member
Its stuck in a forward gear as well as being in reverse so the two are working against each other.
Sure what it sounds like. That is exactly how a trans brake works. I am not sure how they hydraulic circuits are exactly on the 4R100's, so don't know if they use shift solenoids for every clutch pack apply, or only for shifts. If they use it for every hydraulic action, then it could be a solenoid.
I see. Will have to check it out. I did some research and found out the first numbers on the tag is the build date, vehicle it was used in and auto trans. In my case, I have a sticker that says F8up 98 van auto. What I cant seem to find is what the last 2 mean. Like, Mine is F8UP-BA. Whats the BA stand for, anyone know?