PROJECT - Make 5R55E hold decent power (400-450 HP / Torque) | Ford Explorer Forums - Serious Explorations

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PROJECT - Make 5R55E hold decent power (400-450 HP / Torque)


Explorer Addict
May 6, 2006
Reaction score
City, State
Huntsville, Texas
Year, Model & Trim Level
01 Sport
As the title says....I'm determined to make this Transmission hold this amount of power. I know most guru's don't like the 5R55E and probably think it's a lost cause. The problem I have is I'm pushing this Transmission to the limits without a problem. James has pushed this Transmission to the limit and started to get some slip. This was at higher boost levels from his turbo. Was it because of the mileage? What exactly are the limits? Has anyone ever broken this Transmission with decent power? (I’m not talking about your normal failures with a stock engine - I'm talking, got on it hard and it came a part) The 55 in the name means 550 LBS of torque, correct? Then why can't this Transmission hold that and who has really found this out? I've searched and searched (many forums) and there is still no solid proof that the failure was the Transmission itself. In fact, I've seen threads where someone would swap to another Transmission (a so called bullet proof Transmission) and self destruct that one as well. That tells me a driver variable was in place and the info about a bad 5r55e Trans get's thrown out the window with that.

From my knowledge learned in this forum, the 5R55E technical design is not as good as some of the newer trannies, like the 5R55s or w. If it were, there wouldn’t' be a need for the S or W. So you see my delimia here?

Here is my plan.

1) Get a Transmission cooler with a fan - I'm thinking about this one -

2) Deep Tranny pan & tranny temp gauge. *note - tranny pan requires a 4X4 filter.
Here is the pan I purchased -
Here are actual pictures of the cover. This is a very solid pan; very heavy duty construction. -
and gauge purchased -

3) Do the shift correction kits on the Transmission, OR

4) Possible get a rebuilt valve body? There is a place online that offers a towing valve body upgrade. - What do you think about this one?

5) Work on the the tranny tune. The goal here is to keep the torque convertor locked as much as possible to reduce heat and reduce the torque on shifts.

Torque_Converer_Lock_Unlock Schedule.JPG


Lastly – Check and check and check….Service. Service. Service.

- Adjust bands every 10-15K -
- Change fluid every 10-15K

The bottom line is, I’m fighting to not have to swap transmissions. If I have to, then I do but I’m not completely sold the 5R55E can’t handle the 450 MAX HP and 550 Torque. I really do not attend to make this much power so I’m just setting some fluff.

suggestions are welcome.

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I'd do the cooler, pan, and VB kit, plus all upgrades from Sonnax etc. Skip the VB swap unless you have issues to fix, or don't know how to work through a VB. I'd add a trans filter also, before the radiator if you don't have issues.
Below is in my 1999 trans filter. I since found a Hayden adapter with horizontal sideways outlets, for my Mountaineer.


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Connect a transmission temperature gauge, and use a stacked plate cooler. Synthetic fluid is recommended. An electric fan might help to regulate the temperature better. Another thing. In the valve body, there is a temperature regulator for opening, and closing the flow of fluid to the cooler at certain temperatures. They make a bypass for this.

... In the valve body, there is a temperature regulator for opening, and closing the flow of fluid to the cooler at certain temperatures. They make a bypass for this.
That is a positive feature of the 5R which warms the fluid faster. If it functions than it should be left alone.

Still, there is no need to alter that unless it malfunctions. There are plenty of things to work on besides that. I'd suggest trying to get a new EPC solenoid, preferably the new design which we tested here.

Please fill me in on this EPC solenoid. I must of missed the thread.

Please fill me in on this EPC solenoid. I must of missed the thread.

Here's the link, it was last November.

I have one and it had a slight affect on shifting, but I already had a new Ford EPC installed 10k before that. Others reported great improvement in shifting, but also had a lot of miles on their old EPC's. The EPC solenoid does show signs of wear in most 5R's with high mileage. It's the #1 part that you should change besides a VB kit. I don't know if they have yet produced them for mass sale.

Good for you. I want to do the same so I will be watching this thread.

If you can make it hold that much horsepower, how about making it so the A4LD can hold 160HP?! Haha good luck with your project

CDW - Great thread. What happened it died down and left me in limbo?

Only a few people completed their survey I believe, there weren't any results posted.

Huh? these guys go out and give free parts, it seems as though they should have completed the survey, at a minimum. great.

The surveys were emailed to them insted of being posted. There were actually 2 new designs of this EPC solenoid. Both look very similar to each other. Internally, the second one has a larger orifice, and is set to regulate a higher amount of pressure.

Jakee, couldn't agree more about the 5R55E. James dumped tons of power though his. It didn't fail until many drag strip/dyno runs. This is wear at or near the limit, not outright failure do to too much power. I tow heavy and plan to use this tranny til failure. I spoke with Saleen about the other 5R55 trans, they work fine with much more power with a simple torque converter change. No warranty problems.

I doubt the 55E will take 550 LB/FT. The friction material isn't up to the task and there isn't enough surface area. We can't change that but in the absence of drag strip abuse, nothing else should fail. Do to power that is! They should still take everything our SOHCs can through at them if we keep them cool and well maintained.

I agree with CDWs list of mods but don't plan on doing them myself until I encounter problems. I personally wouldn't bypass the internal temp regulator but it depends on how you will use your truck. Im normally aspirated for now but once the engine is finished I'll still be making serious power (think heads, cams, the works). The supercharger (TVS) will probably still be a year or more out, and then only if I still need more power to tow.

Don't forget to keep the selonoids cool to. Not just the fluid. Shield them from the exhaust.

Good tips. One thing that might be helping me with the Trans temps is the Y-Pipe is wrapped with header wrap, which keeps the heat in the pipe to the turbo and away from the tranny. I'd much rather have to re-do a y-pipe every once-in-awhile, than heat up the tranny; although, the y-pipe is holding up fine under the heat. But, it’s not to good as far as rust. After awhile, the high heat paint can't take anymore and let's go. Condensation then get's trapped in the wrap and the rust process is accelerated. I really need to make up a stainless version!

I'll never get anywhere near 550 LBS of torque.

Being a big fan of James 5r55w/s swap, James stated that during regular maintenance he maintain the bands regularly.

My bands looked like rubber after 125k and I believe this is another factor in failure, more slipping and heat then needed.


Subscribing - this will be interesting.

Everyone is subscribing to watch me blow my tranny up?

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I just had an idea... from what I can tell your Explorer is a streeter, no offroading. In computers they use heat sinks to dissipate heat, just like the cooler you're planning on. I was wondering if there's maybe a way to adapt a few heatsinks to transfer heat directly away from the transmission before going into the cooler. Make any sense? I figure if it's going to stay on the street, there's wouldn't be that much to worry about, could probably be designed to just break away if something did hit it to.