inh's 5r55e internal thermostat bypass how to

[inh]

A well known fact among people with experience with the Ford 5r55e transmission is that it has an internal thermostat that blocks fluid flow to the radiator until it reaches a temperature of 150-175 degrees Fahrenheit. I believe the spec is 150 degrees, but personally mine doesnt open till 175, far too high in my opinion.

As seen in this thread most people see transmission temps significantly lower than the 175 I get. And once I start offroading, or hauling a truckload of junk up a hill on the highway, temps go up to 220, even as high as 230 sometimes. I have added an external filter, as well as a b&m cooler so seeing 230 degree temps was somewhat of a surprise. I think this is because at 175 constantly, it doesn't take much to heat up to much higher and more dangerous temps.

There is some controversy over whether or not it is a worthwhile mod to do, and only time will tell for sure. If you live on the north pole, maybe not such a good idea, but I think for most climates it's fine.

Superior makes a shift improvement kit that includes a small metal piece to bypass the internal thermostat. I THINK it keeps a little plunger from plugging a hole in a valve below a set temperature. Somehow, this allows fluid to flow to the cooler all the time.

 

[inh]

Installation is very easy, assuming you already have the valve body removed.

 

[Runnin'OnEmpty]

Inh, I did this mod to mine several years ago, and about
80K miles ago. At the time, I debated whether or not to
eliminate the thermostat, but I did on the basis that auto
transmissions had no thermostat for well over half a century,
so why mess with something that had already worked so
well for so long.....?

The Explorer has been driven in all kinds of weather ranging
from 0* to 105*, with no apparent transmission troubles and
has shifted fine in all temps (for the past 80K miles).

At the time of the trans work, I was trying to cure a 1-2
shift flare, and also used the Superior kit. The thermostat
elimination was incidental to the other work I did, and I
had almost forgotten about it until I saw your pics.

Just giving my long-term experience with the mod, for what
it's worth.....

 

[inh]

Appreciate it! Now get yourself a temp gauge installed in to the trans pan and lemme know what your temps are

 

[BrooklynBay]

Thanks for making this thread! I'm going to make it a sticky. One thing I'm wondering about is why they would add a part to keep this plunger open instead of recommending removing the plunger in the first place.

 

[inh]

You cant remove the plunger. I noticed when I removed the VB this was installed in that the little plunger was sticking out, and this spacer was keeping it away from a valve with a small hole in it, that looks like the plunger would fit in. The plunger is probably .5 mm thick, and extends over 1 CM out from that big brass piece you see me holding. No way to remove it I don't think..

You can kind of see it in the pic, its the bare steel pin stickin out a bit. I pushed it in to that point, it was out a bit further..

 

[CDW6212R]

Psst, how many posts have you got? Look now before you do post again.

It's a good thought, to check the trans temps. I should do that with my work truck to be sure also. That's a very well done diagram of the part, and I wonder if they sell it separately.

 

[duggyd123]

where can i get a new transmission thermo0stat

help me please my fluid is dumping out ever couple hundred miles and is very hot(smoke billows from under hood. if i refill the tranny it works fine but then it just dumps unexpectedly and i cant figure out why

 

[BrooklynBay]

The part comes in the Superior kit.

 

[duggyd123]

how much

where do i get the superior kit and how much is it

 

[BrooklynBay]

Check WWW.TransmissionPartsUSA.Com or WWW.BulkPart.Com.

 

[duggyd123]

so does our tranny have a thermostat???

 

[BrooklynBay]

Yes, you have an internal thermostat even though you have a 4R55E.

 

[Fredness]

Superior appears to have redesigned the Thermostat Bypass plug. The dimensions have all changed (minor), but the I.D. which is now .315" instead of the .105" listed.
I was going to have a bypass machined locally. Good thing, now I got the update.
I'll compare the kit to the Sonnax mods on the CVB valve body and do the ones that don't overlap. Now that I've measured the temps before and after a test run, I have a better idea of what's going on, and will be doing the thermostat bypass for certain - I want to turn the 5R55E in to a full-flow cooling (no internal T-Stat) so that the ATF is filtered 100% of the time and not just when "hot".

 

[ranger7ltr]

Did you discover the thermostat bypass changes by buying the kit?

I have a valvebody from Central Valve Bodies and really wanted to add the thermostat bypass before installing it.. I wrote to Superior and not surprisingly they will not sell just the thermostat bypass piece...

So it looks like I will be buying their kit just to get this piece to install before installing the valve body from Central...

Would you know when they changed the design so I be on the lookout for earlier kits with the first generation bypass plug?

 

[Fredness]

I don't believe they are "gen" specific, I believe it was a "all" change as there are no part numbers or anything else that shows differently.

The specs posted will do fine, just make sure the I.D. is .315 (.277 was the O.D. of the part it captures - IIRC). I'm sure it is just a spacer, so as long as it fits over the end of the plug and in to the spacer, you'll be good.

Sonnax appears to have addressed this same issue in one of their updates: Boost Valve and Sleeve kit 37947-01K/-03K; "Low Cooler Pressure at idle, overheat conditions". This jives with what Superior told me was the reason for the part. With this info, I am less inclined to use the "Thermo Blocker", but we'll see.

The one I had turned locally was from an Russian AK-47 Gas Piston - pix to follow...
PM me if you are interested in the kit.

 

[ranger7ltr]

So does the Sonnax increased ratio and sleeve change the cooler flow or just increase line pressure? I am interested in getting a way to change thermostatic cooler flow to constant flow through the coolers I have on my truck...

I will PM you in a bit FREDNESS...

 

[Fredness]

It increases cooler flow, especially at idle.
Apparently the issue was not enough cooler flow at idle causing the trans to overheat. Sonnax looks like they attacked that problem by increasing the line pressure at idle, so there is better flow. The Sonnax website has a document that shows ATF Cooler flow in GPM and there is flow, even with the T-Stat closed. This is similar to other set ups and it avoids air-hammer, bubbles, and other issues.

Superior solved this by running the cooler loop all the time. Not bad, just a different fis. Provided you have a cooling system set to work that way, it's good.

If you want constant flow, the Superior "Thermo-Blocker" is the ticket. The Sonnax mod would work WITH this for even better results.

 

[ranger7ltr]

I saw the charts from Sonnax and I am sure any flow through the cooler is better than no flow at all...I am assuming that since you are making the thermo blocker piece you are going to a full flow setup?

I have added a stacked plate B&M tranny cooler as well as an external filter on mine and honestly I can't see a problem with cooling the tranny fluid too much...At least not here in Texas...

Comparing the initial cold flow to full temp thermostat open flow, according to the charts, is that even with the thermostat closed you would still get about 30% flow into the cooler and even with that fluid being cooled I wonder how much longer it would take to fully open and keep it open with an additional cooler...

So how long before you run your mods in the Central Valve Body? I know I am interested to see what you find...

 

[Fredness]

Viscosity is lower as heat rises, then (eventually) is gets too hot and the process reverses.
Amsoil ATF is 38.9 Kinematic Viscosity @ 40°C (104*f) and 7.6 Kinematic Viscosity @ 100°C (212*f). For best mileage and filtration, I want the lowest viscosity and higher temps.
I think that if I keep it near 180*f, this should provide the best filtration (lower particulates) and theoretically increase MPG while reducing wear.