I just got a 06 Mark LT with 4" pro comp lift and 35" tires a few months back.  Got it from the dealer and not sure if rear end was re-geared(probably not).  Anyway, I'm pretty sure I burnt the tranny off road in the mud (HAD A BLAST).  

Long story short,  when the tranny gets warm, it slips on the 1-2 shift.  Luckily the truck is still under warranty but it's been in the shop for 6 weeks...Ford is giving dealer a hard time about replacing the tranny and the dealer has replaced the following:

1.  Torque converter
2.  Valve Body
3.  Piston
4.  1,2 and overdrive bands
5.  Int. 1 way clutch
6.  Front pump

At this point I think I'm just gonna replace the tranny on my own.  It has the 4R75E.  Can you guys recommend if I should rebuild, replace and if so what should I do to make it handle off-road.  I'm in FL so we're primarily in the mud with the wheels spinnin!

Thanks,

Milt  

The problem is not the tranny being completely replaced because even a new one will fail two unless you regear the axles in truck properly. (Ford knows this too and why they did not want to start down path with new trannies for it) Many never bother to regear then blame tranny when it fails. Slap in some 4.88 gears in axles and you will not loose any more trannies running mud and Ford will likely replace tranny in future when they see that you have taking time to prevent future occurrence of problem. Mnay never even remotely consider the extra load that big tires place on trannies when they do not regear axles.  

That a bunch of bull I know a lot of guys that have 35s on there trucks and wheel them often and never had the rear cover or even changed the fluid in there trans. The only problems ive ever heard of involves the cruise control not working.I have 35s on my ranger with no mods but a lift with the crappist trans on the planet and it hasn't failed yet with 115000 miles on it  

bet that's a turd.    

fatguy4X4:
bet that's a turd.  

I'll bet too plus his weak engine has saved tranny as it struggles down the road.  

Once Ford replaces or fixes the tranny, I would replace the gears ASAP to either 4.56 or 4.88. The last thing you want is your warrenty to run out and the tranny go again. These gears will put the engine and tranny back close to stock RPM and your torq converter will love it, much less headaches in the future.  

a good friend of mine is a blue oval cetified master mechanic of over 20 years experience in a Ford service dept. he tells me all the time how ford is terrible about backing up their warranties. especially if they find a good excuse like this. "oh, well, this guy has been wheelin' and hot roddin' and tore it up, we don't support this kind of abuse." or "oops, he was 2 miles past the 3k mark for changin his oil, he neglected it. were out!!!". oooh, sorry, thanks for playin' the correct answer was "yer screwed!", here's a copy of our home game. Johnny, tell the audience what else he gets just for being on the show...      

wjsuter82:
Once Ford replaces or fixes the tranny, I would replace the gears ASAP to either 4.56 or 4.88. The last thing you want is your warrenty to run out and the tranny go again. These gears will put the engine and tranny back close to stock RPM and your torq converter will love it, much less headaches in the future.

Good advise. BTW it is not the RPM per say but rather the reduced average torque load that deeper gears place on drive train. Big tires with tall stock gears is kinda like pulling a heavy trailer all the time with stock tires as far as the torque load it places on drive line.