understanding 5r55e fluid flow - troubleshooting weak engagement in D

[hummvee2134]

Hey everyone,

First post here. The info on this forum helped me through my first rebuild of an auto trans, 5r55e in my case. Things went well but i do have an issue. Here's the story:

Previous to the rebuild, i had some light flaring in 2-3 and 3-4. I had swapped in an ebay valve body a year ago which seemed to help (possibly it was just the fluid change that helped things) and i found a lot of clutch material in the pan and in the valve body. It got worse again (a year later, now) and i knew what it needed.

I did a full rebuild but i didn't touch the valve body. New piston seals, soft parts, etc...

I tested everything on the bench after putting everything together. All pistons moved with ease under 20psi

Now that it's all back together, i've found that it will drive great for the first 30 minutes. Every shift is crisp and clean. I've never felt it so perfect. After this 30 minutes, i get a very light engagement in 1st gear in D. Manual 1st works fine. Reverse also works fine. All other gears seem good once it's rolling.

The issue only seems to happen once the transmission is warmed up. My scan tool put it at 190 degrees. The issue was not reproducible at 160 degrees.

The weak engagement in 1st threw a p0731 - first gear ratio incorrect. My scan tool showed about 2000RPM of torque converter slip which is really just transmission slip.

I just dropped the valve body hoping to find something up in there but everything seems alright. i did use some syl glyde to hold the gasket on the separator plate previous to installation in the case. It seems like that syl glide may have built up a bit and i'm wondering if that's causing a leak. Also all bolts on the VB seemed tight upon removal.

I'm going to test the drum with air once again with it in the car to rule that out again.

I'm thinking maybe there's a valve body leak that's happening only when the truck is warm.

That aside, can anyone think of a reason that D would slip but manual 1 would work? They both use SS1 (forward clutch) and manual 1 uses SS4 (Coast) for engine braking so one wouldn't think there could be any difference.

Does anyone have a diagram showing fluid flow through the valve body on a 5r553? I'm thinking maybe if i can understand the routing of fluid a little better in D, i can narrow my troubleshooting to a more specific area of the unit.

Thanks in advance, everyone.

 

[JK080]

Did you inspect the pump?

This sounds like low line pressure when hot, check your pressure regulator valve and the forward engagement valve in the valve body.

Check line pressure once back together, you don't want to see less than 65-70 for a minimum in drive, if it's low I would suspect the pump.

Its expected to have a higher line pressure for reverse and manual low, this could be why the delay is gone in low.

Make sure the torx bolt is tight in the case under the valve body a leak here can cause hydraulic leaks.

Let us know what you find

 

[CDW6212R]

Jame's suggestion to check the fluid pressures is wise, that's a best first check from what you have done. Hopefully that tells you something. Did you install a Sonnax PRV for that trans? It's one of the few upgrades available for the 5R55E.

Are you really seeing 190 degrees in the fluid? I thought with the 150* internal thermostat, it wouldn't get much higher than that. That doesn't help you with that symptom, but I'd rather not see temps anywhere near 200*.

How closely did you look at the gasket, in the areas that are common to blow out? Sonnax believes those gasket issues are due to the case in that area rubbing/wearing on the gasket, from vibration. The case is very deep in those areas, the aluminum walls of those fluid passages are thin and deep, allowing too much movement. You're issue is not likely from that, I just point it out as something all 5R55E tear downs should consider. Sonnax suggest installing set screws as an object placed between the worm tracks(passages) to keep them from moving.

 

[hummvee2134]

Thanks for your replies JK and CDW.

JK, i'll ohm out the EPC valve and inspect it. What should i look for on the forward engagement valve? bore wear or that kind of thing? I just ordered a pressure gauge so i can get those values once it's back together. I'm waiting on a fresh gasket to come in the mail anyways... hopefully just a few more days.

I also did just test the forward clutch with 20PSI. It engages nice and strong, if a pull the air away it poofs back at me so it's holding air pressure too.

CDW- I didn't touch the valve body at all actually. I had purchased this valve body off of ebay as a remanufactured unit about a year ago. When i had some flaring in 2-3 3-4 etc, i was hoping i could swap it in as a quick fix. It did help a lot, but i'm attributing a but of that to the fluid change. It did speed up reverse and forward engagement by a considerable amount too.

The separator plate to case gasket was a new transtec that i put in as part of the rebuild. I used a bit of syl-glide to hold it on there while installing it... all of that syl-glide was still there upon removal. i can't help but wonder if that was at all related. The separator plate to valve body gasket was not new. It did tear just a little bit on a corner (by a bolt hole) during removal. it was definitely a year old but didn't seem to be broken or torn while installed.

Yeah it was actually 190. I didn't think that was a problem though. I've seen a few images depict that as an okay operating temp for a transmission However, those aren't specific to the 5r55e

Thanks again. I'll report back with what i find.

 

[CDW6212R]

Are the solenoids all new, if not I'd replace them this time. The EPC is very expensive, but not what they used to cost. Be sure to get the Borg Warner EPC, which was a new design in about 2007 or so. That is a critical item in any 5R55E.

If the VB is unknown but rebuilt, I'd consider doing the VB kit again, maybe even find out what they used for it. There are only a few upgrade things possible for these 5R's, and it's all in the VB. Sonnax is a good site to see what's available, most of what they have is reasonable, or very high because it's correction parts(tool required).

That 190* temp you have might be normal, no one ever reports what their temps are, but we hear a lot of the 150* T'stat built into the VB.

 

[hummvee2134]

I really wish i hadn't thrown my old VB away. My truck is an 08 so it probably did have the newer model EPC. That's probably not the case with the re-manned one that i bought.

Can you guys recommend a good source for a complete re manufactured valve body? Maybe it would make more sense to just swap it out entirely.

 

[Ngrimm]

Thanks for your replies JK and CDW.

JK, i'll ohm out the EPC valve and inspect it. What should i look for on the forward engagement valve? bore wear or that kind of thing? I just ordered a pressure gauge so i can get those values once it's back together. I'm waiting on a fresh gasket to come in the mail anyways... hopefully just a few more days.

I also did just test the forward clutch with 20PSI. It engages nice and strong, if a pull the air away it poofs back at me so it's holding air pressure too.

CDW- I didn't touch the valve body at all actually. I had purchased this valve body off of ebay as a remanufactured unit about a year ago. When i had some flaring in 2-3 3-4 etc, i was hoping i could swap it in as a quick fix. It did help a lot, but i'm attributing a but of that to the fluid change. It did speed up reverse and forward engagement by a considerable amount too.

The separator plate to case gasket was a new transtec that i put in as part of the rebuild. I used a bit of syl-glide to hold it on there while installing it... all of that syl-glide was still there upon removal. i can't help but wonder if that was at all related. The separator plate to valve body gasket was not new. It did tear just a little bit on a corner (by a bolt hole) during removal. it was definitely a year old but didn't seem to be broken or torn while installed.

Yeah it was actually 190. I didn't think that was a problem though. I've seen a few images depict that as an okay operating temp for a transmission However, those aren't specific to the 5r55e

View attachment 151764

Thanks again. I'll report back with what i find.

For what it's worth, mine doesn't go over 163 degrees with the temp outside in the 60s. Unfortunately my engagement problem begins at around 150 degrees.

 

[hummvee2134]

Hey Everyone.

I put the valve body back together last night. EPC solenoid looked good and also ohmed out. That's all the testing i did on it.

I tried to remove the forward control solenoid. I popped the clip, retainer (which fit very loosely by the way) and spring out. I worked the piston almost all of the way out, but something on it was stuck preventing it from coming out all of the way. I blew it out with air to make sure there was no debris in there and there didn't seem to be any bore wear either. The piston seemed to move freely within its operating area so i figured that was likely okay and reassembled everything.

I put the valve body back in, filled it up, fired it up and it seems to drive like it does before. I didn't get a blinking OD light or anything, but it does feel weak.

The pressure gauge came in too. The line was a little short so i had to look out of the window and down to see it. I had my girlfriend come with me and take notes of what i was saying so i apologize for the lack of granularity. It was a quick drive.

These are all from the line pressure port:

Idle: 100psi
Reverse: 175-200psi
Drive: stopped, 100psi
Second gear:150 psi
First gear about to shift to second 75psi
wide open throttle from about 30mph was about 110psi

So overall things look pretty low. I'm really wishing i had taken that pump apart now.

Thoughts?

Thanks again.

 

[Ngrimm]

I feel your pain. How does the EPC pressure look?