high-mileage 4R55E rebuild - what parts to replace in addition to basic rebuild kit? | Ford Explorer Forums - Serious Explorations

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high-mileage 4R55E rebuild - what parts to replace in addition to basic rebuild kit?


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September 6, 2005
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Hello, I have a '96 Explorer with a 4L55E and 236,000 miles on the clock without ever a problem or even a trans fluid change (:confused:). It drives perfectly in all forward gears, but has suddenly started slipping in reverse. With so many miles on it, I don't intend on chasing down the problem, and I suspect that a fluid change at 236k miles would kill the transmission anyways.

I intend to purchase a 4R55E core and a rebuild kit and rebuild it myself hopefully before reverse dies completely in my old trans. My question is, what additional parts will I need over the basic rebuild kit? What other parts would be good to replace even if they appear to be working (solenoids, etc.)? What else needs special attention in this transmission that isn't listed in the rebuild manuals?

I'm not familiar with the idiosyncrasies of this transmission, so any advise would be appreciated!


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Welcome to this forum! You could add bands, servo pistons, one way sprags, washers, torrington bearings, bushings, pump gears, hard parts with wear, solenoids, and the internal wiring harness. Some of these parts could still be good, so check them before scrapping them. It would be recommended to replace them so that you don't have to do another rebuild after only using it for a short time.

Cool, thanks for the reply! I do want the rebuild to last a while, so I intend to replace anything that appears to have wear. But some parts are gray-areas, like solenoids or parts with known design flaws that should be updated to newer designs or modified by the rebuilder. My old trans lasted 236,000+ miles without a single problem (and now only reverse is slipping), and a decent part of that mileage was spent towing around a decent size ski-boat or race car trailer. I've been very pleased with the durability of this transmission, but from reading around on these forums and others, it looks to me like this trans was a "fluke", and most of these transmissions can't be expected to last as long as this one has, especially when towing as much as I do. I want to do whatever i can to make the rebuild as dependable as my old trans.

Clutches, bands, sprags, washers, bearings, bushings, seals, pump, and tq converter - all these parts appear to be standard items of replacement in a full overhaul. I'm not looking for "performance", just durability/dependability. Are there any brands of parts that I should pay attention to? What peculiarities should I be aware of when going through this transmission? Would the Transgo or Superior shift kits help? Thanks!

There are heavy duty parts which are considered performance parts like Kevlar bands, Kolene steels, etc. The rear snap ring, roll pin which holds the shift lever, and the center support seals are a little tough to reinstall. Make sure that the torque converter is fully seated while reinstalling the transmission. Flush the front cooler with cooler cleaner before reinstalling the rebuilt transmission.

BB is good in his advice... but I would STAY AWAY from Kevlar anything - friction material wise. FORD stock friction or reputable aftermarket (Raybestos - Borg Warner, for ex. - is fine)

i am also looking to rebuild my own 4r55e is their any special tools needed i want every thing ou can replace replaced in it any one ot a good master rebuild kit place .