Eratic/hard shifting 5R55E transmission

[4X4XFD]

Hi. A little background seems appropriate first. I bought my used 2002 FX4 in 2005. It had been a fleet vehicle and had 70K miles on it when I bought it. I took it to the local Aamco shop of whom I knew the owner soon after purchase and had them drain/fill and change the tranny filter. Honestly, I've been negligent in the tranny maintenance since then. The truck now has 151K miles.
About 2 years ago I headed off for work at a place about 30 miles away. After a couple of miles I stopped a stop sign, and proceeded on. The 1st to 2nd shift was extremely hard and I noticed the OD light started flashing on the dash. Sensing the OD wasn't working I keep my speed on the highway to about 50 mph. I got to my workplace and when lunch time came I checked the tranny fluid level. It seemed low so I limped the truck to the closest Walmart and bought a quart of fluid. The truck shifted extremely hard every time from 1st to 2nd on the way. I added fluid and it seemed to be better on the way back home.
Since that episode it's continued to have occasional 1st to 2nd and into OD hard shifts. Not all the time, and I try to accelerate slowly as that seems to help it from hard shifting.
I don't sense any slippage of the tranny. So I'm wondering if the software is doing as it should but some malfunctions, perhaps because of wear, in the valve body is causing the erratic shifts.
My research today lead me to a company named Sonnax.com. From the articles I saw it seems they have a goof understanding of the fluid dynamics involved in auto transmissions....perhaps especially the functions of the valve bodies. Has anyone heard of them or have any experience with them? Their most local distributor to me is in Tulsa OK. I'm thinking of giving them a call. Maybe....just maybe...a professionally reman valve body will resolve the issues?

 

[manley]

bump... I'm experiencing similar hard shifts from 1st to 2nd in a 97 Ranger with a 5R55E transmission.

 

[CamTheHedgehog]

While I am by no means an expert, I have taken my automotive transmission class on my way towards my auto technician degree, and have watched a number of videos on the 5R55E.

First, keep in mind that "2nd" is not really second. It is simply made by engaging the overdrive band while in 1st, adding a bit of gear ratio to effectively create second gear.

So something to check first is the adjustment of the overdrive band- it is simple to do and can be done in the truck, search on YT for a video.

Second, the valve bodies are known to be problematic on these transmissions, especially on the early ones- they would blow out the VB gasket and lose gears. The shift valve and check ball can malfunction or stick, and the servos (one for intermediate and one for overdrive) also can stick in their bores or bypass fluid, causing either loss of a gear or rough shifts. The servos are very close to the catalytic converter and over time the seals on the piston will brittle due to being cooked by the heat.


The fact that you are having both 1st to 2nd issues as well as 4th to OD issues tells me it is definitely an overdrive issue, either the band itself or the control of that band.

Sonnax is a good company, their shift kits are well known.

 

[manley]

Thank you for your explanation, Cam. It looks like there is some good information on the Sonnax website. I am leaning toward replacing the servos, but am unsure how to know which part is correct for my 5R55E. Do they all use the same part or are there variations I need to be aware of? Thanks again for your help.

 

[CamTheHedgehog]

Thank you for your explanation, Cam. It looks like there is some good information on the Sonnax website. I am leaning toward replacing the servos, but am unsure how to know which part is correct for my 5R55E. Do they all use the same part or are there variations I need to be aware of? Thanks again for your help.

No problem! Happy to help.

Yes, there are a handful of variations to the servos, to the diameter specifically. There isn't much rhyme or reason that I know of to the variation, just that generally the older variations of the 5r55e's use smaller servos. The only way to really know is to get under the truck and look at the transmission.

Under your truck, look at the passenger side of the trans. The exhaust might get in your way a bit. You should see two small metal covers- these are what cover the bore that the servo piston rides in. The covers look like this.
One is for the intermediate band, the other is for the overdrive. I.... don't remember which is which. I'll get back to you on that one.

And here is an image of the passenger side of the trans so you know what to look for.

Once you get a good angle, look for a two-letter code on the covers. The one above is code AB- one of the larger and later servo pistons. The two servos on your truck may be the same size, they may be different. All depends on how old the trans is.

Write down those two letters for each cover, that is how you will order the servos.

The other thing to do is to measure the bore with calipers- if the bore where the piston rides is worn out or damaged, replacing it won't solve your problem (at least not all the way).

Once you've found your servo codes, you are good to go!

 

[CamTheHedgehog]

Here is also a good article from Sonnax on troubleshooting these transmissions.

18 Troubleshooting Tips for 4R44E & 5R55E Transmissions | Sonnax

With the proper repair, these cores can be just like money in the bank. Set yourself up for a successful rebuild with these expert tips.

www.sonnax.com

 

[manley]

Thank you for the help! Knowing the code on the cover identifies the needed part is very helpful!