4r100 repair/rebuild/replace

Tadias

Member
Joined
Jul 3, 2023
Posts
13
Looking for opinions about a repair, a rebuild vs a more robust replacement. I have a 03 E350 7.3TD w about 107k and it started stalling when placed in reverse after driving. My initial thought was that it just needed a new torque converter but the in situ test showed varied pressure in different gears so the guy wants to bench test the tranny. He thinks repairs could be one of three problems none of which sounded like they would break the bank and that yes the TC is failing.
My question is with 107k on my drivetrain with a 10k lb rig that sometimes tows and often is running slow, steep, demanding and remote 4x4 trails what’s the better solution? My understanding is that the 4r100 WAS Fords solution to its weaker predecessor but is that also the solution for the rig in its current state? A lot of work has gone into into making this thing as tough as possible. D60 front and rear, lockers/LSDs, custom suspension w lift, functional rock rails, underbody armor and skid plates, 4” exhaust w BD brake etc. so I’m not averse to spending money but if I’m just throwing money at it for no good reason then that’s dumb. Is a functional 4r100 a perfectly fine transmission? How many miles do they typically last? Any input is helpful.
 
What do you have in mind as an alternative? 5R110? 6R140? Allison?

I talked to MG about a 5R110 swap when I had my 7.3. He was in touch with a company that was working on it using an external controller. Not sure if it ever came to fruition.

Could you do a 6R140 the same way? Would be pretty sweet if you could. I imagine better performance and mpg at the same time.
 
4R100 is a perfectly capable tranny for your rig. 200-300k is common. Early failures happen.

With your use case I would have a specialty transmission builder rebuild yours, buy once and cry once. It's by far the simplest and most straight forward option.

I can't remember ATM who the great builders are, John Woods comes to mind, there are a few. I'd go this direction over trying to put a newer tranny in in a heartbeat and avoid the pitfalls and expense of fooling with electronics and wiring harness.
 
I *think* John Wood retired? I put in one of his valve bodies along with a +7.5qt MagHytec pan to hopefully extend the service life of my 4r100 which sees a fair amount of towing (15k combined), currently at ~185k miles. I've tried to keep a finger on the pulse of 4r100 rebuilders should the need arise, and these days it looks like BTS (Brian's Truck Shop) is among the top contenders.

It sounds like a fresh torque converter and a modified valve body might address your issues though? Throw the biggest cooler you can fit (Trucool 40k is a great option) on that list and I'd probably not worry too much.
 
Between towing and running “slow, steep, demanding, and remote 4x4 trails” I’ll also endorse the idea of installing a larger trans cooler (as TheLetterJ suggested) while you’re addressing your Trans issue…temp’s for my transmission were the first to reach critical limits in most of those scenarios.
 
Thanks for all of your input. Yeah it’d be sick if it was easy to swap out to a six speed but sadly I think that’s beyond the scope of this project. Sounds like I’m hearing that the 4r100 with an ‘enhanced’ sort of repair/rebuild is the way to go. So with the Hydra chip I’ll run the engine up to around 400hp aside from better valve bodies should I consider better planetary gears as well? I’ll also make sure to discuss the larger cooler too.
Anyone want to chime in on the TC stall speed? I’m debating on 1600 or 1800. I’ve read that the the ideal for the 7.3 is 1600 (peak torque) but a turbo won’t spool up if the stall is low and I am running a stock turbo which I believe is non VGT so higher?
 
You need to address the root cause with programming. Ford allows the transmission behind the 7.3L to run unlocked in any gear depending on throttle position, and this is where most of the heat comes from (aside from crawling). But… I don’t know who even does 7.3L programmers anymore.

FWIW - The 4R100 will last a long time once a TruCool 40k is installed and the lockup programming is addressed. Mine is original still, currently at 521,000 miles. Probably close to 350,000 of those were towing, often with a combined weight close to 25k.

As far as adding more gears… It doesn’t seem viable yet. US Shift tried a 5R110 controller, but the swap-shift-sequence is so touchy, I suspect they blew up a few transmissions before calling it quits. They do have a 6r80 controller, but not a 6R140 version. And doing an Allison would require an expensive adapter plate and driveline changes.
 
John Woods is retired, no longer rebuilds tranmissions.

Ford used to offer an HD rebuilt trans, but unfortunately, no longer. Just a standard rebuild.

BTS is considered the holy grail, absolute best rebuild you can get for a 4R100.

Sam Wyse is well regarded as one of the top.


As previously mentioned, cooling is critical for the 4R100. The go to cooler for the Superduty trucks is to use the trans cooler from a 6.0 truck or Mishimoto makes a cooler for the 7.3 superduty. I am not sure if either of those will fit in the van.
 

Try RV LIFE Pro Free for 7 Days

  • New Ad-Free experience on this RV LIFE Community.
  • Plan the best RV Safe travel with RV LIFE Trip Wizard.
  • Navigate with our RV Safe GPS mobile app.
  • and much more...
Try RV LIFE Pro Today
Back
Top