I got this car used ~ 130,000 miles on it then n the guy spent ten minutes under the hood looking for the tranny dipstick when I asked him to check the fluid. It was a test to get an honest idea from him if he had ever had the tranny fluid n filter changed cause it’s a closed system. I put about 20,000 more miles on it and never ever one time did the tranny slip. I run it hard. It’s Nascar every time I get behind the wheel kind of running it hard! On personal recommendation I took it to a car care center n had the tranny fluid n filter changed. They seemed knowledgeable and competent n I know the difference. I noticed that day (10 days ago) that I had a new hesitation when I put it in drive n I called them the next day n as I was thinking the guy told me new tranny fluid in an old transmission plus it’s winter here. Slip shows they added only 4 quarts of new fluid so not a complete flush done which is good. I drove it about 3 hours round trip five days ago n no real issues just the hesitation when first put in drive. Today the next time I’ve driven it n I’ve had hesitation in both reverse and drive and it slipped a little going up a hill n the car was warmed up drove it a couple miles before the hill even. This transmission has never ever slipped. My first thing is to have it checked to see the tranny has enough fluid in it but my question is given it’s a 2006 model with 157,000 on it would it help or hurt to have just a little extra tranny fluid in it? If it had worn bands this bad to be slipping I would have caught it before ten days ago. This didn’t happen until after the tranny fluid n filter were changed. If it has enough tranny fluid in it, what’s my second step to look at n the third etc?!! I’m a Chevy girl but I love this damn car n I don’t want to ruin the transmission. Tx, Jenny

 

Incirrect fluid level after a drain / refill is the number 1 reason why the 5r55s trans slips. The level can only properly be checked with the car idling in park after it's been shifted manually into all gears, level in the air so you can get under it, and the fluid warmed up.

If you check it when cold or off, the level will be incorrect.

There is Zero benefit in having too much fluid in the tranny.

 

Servo bores are likely worn and are allowing fluid by causing the slipping. They need to be relined with brass inserts. Common problem with this transmission. Look at post # 2 here: https://mustangforums.com/forum/2005...-mustangs.html

 

There are other options these days vs the expensive bore repair.

https:/www.fordservoboretransmissionfixsolution.com/

 

You are right, in fact I did this to my PA streetfighter when I broke a band and the Intermediate servo stem. When I removed the trans and disassembled it, I saw that PA had already installed the brass inserts. I had already received the fix from AJ. With new bands and servos I did install the new o-rings. I contacted AJ and they advised that the new servos with their o-rings and the brass inserts would even be better. I followed Hiram Guterrez videos ( ) in disassembly and repairs along with some suggested enhancements and it's ran like a champ ever since. First time ever working on transmission at 81 yrs. Gutterez videos were perfect instruction.

 

Yep, those Guiterez videos were great for the 5r55s and the CD4 in my old 2006 Ford Escape that I had too!