5R55S slipping from dead stop only?

Cromagnum

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07 GT Automatic, 125k miles trans slipping intermittently in 1st gear from dead stop only? No codes, other than intermittent slipping issue zero issues, shifts perfect through all gears and OD, no slippage or shudder. Recently drained pan and replaced filter, pan was spotless clean too, rechecked fluid level a week later to confirm was correct. Anyone else having this issue??
TIA!

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JimC

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If you are having slipping after replacing fluid then likely you didn't get a full refill. You have to get the transmission up to operating temperature in order to completely fill it and most of the time in DIY cases that isn't done.
 

86GT351

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If you are having slipping after replacing fluid then likely you didn't get a full refill. You have to get the transmission up to operating temperature in order to completely fill it and most of the time in DIY cases that isn't done.
THGis and remeber you have a mix of old and new fluid now. Dropping the pan does not change all 12 quarts
 

JC SSP

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Not saying this is your issue but it’s a very common problem with a transmission with high miles which has had fresh fluid replaced will start to slip. The old fluid had particles and fibers that help engage the gears. The new fluid has none.
 

JC SSP

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Check the fluid per the factory specs before a new/rebuilt tranny.
 

DieHarder

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Might be worthwhile to look into replacing the servo's. Often the bores become hogged out due to the hard metal input shafts on aluminum bores which then leak around the input shafts resulting in slipping/flares. There is a fix that's not expensive. I bought the kit for the day when I need it. You can also try adjusting the bands but if it's otherwise shifting fine they're probably ok.



 

Pentalab

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If you are having slipping after replacing fluid then likely you didn't get a full refill. You have to get the transmission up to operating temperature in order to completely fill it and most of the time in DIY cases that isn't done.
agreed. When cold, the ATF level will read higher on my PA ( performance automotive) after market pan and dipstick. Dipstick comes up on pass side firewall. When up to normal temp, like 170F, level on dipstick is quite a bit lower. PA does not make the pan anymore for the 5r5SS ( only 11+ cars with the 6R80). My PA pan holds an extra 4 qts.

Also added a JDM catch can on drivers side....for the 5R55S...otherwise it will puke atf through the relief. Also added a B+M auto tranny cooler, installed below the oem auto tranny cooler...and both plumbed in series. Was drained by using a combo of light pressure and suction ....on either side of the tranny cooler. That's the only way to get it all out. Replaced with 100% synthetic atf. This is on my 2010 GT auto ....with small roush M90 blower.

If the ATF level is not high enough, when cold, it will slip in 1st gear.... until ATF gets up to temp. Filled to correct level, it won't slip in 1st gear, when 1st started cold.... even below freezing.
 

Autokyrios

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If you are having slipping after replacing fluid then likely you didn't get a full refill. You have to get the transmission up to operating temperature in order to completely fill it and most of the time in DIY cases that isn't done.
Can very much second this. Getting the fluid level right in a 5R55S is a damned art. Even after all the times I've done it, I still make adjustments (adding a fill tube was one of the best things I ever did for the transmission).

To further the diagnosis, if you're slipping from light to medium throttle, but it bites on heavy throttle (and assuming the mechanicals are in good order) you're low on fluid. If it always takes time to bite, you're way low on fluid. If you had too much fluid in there, you shouldn't have issues going but other things will happen (most notably it will spit the excess oil out all over the tranny and undercarriage as punishment for your misdeeds.

There's soo many other factors, too. Good oil level + bad filter = starved transmission. Good oil level + burned/worn clutches = rough or no go. Etc., etc..

Somewhere around here is a post I did with the walkthrough for refilling the transmission, step by step.
 

Autokyrios

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Yes, I knew I was rolling the dice…
Assuming you aren't abusing the transmission (although I would agree that it requires doing) the most common cause of failures with these IMO is heat. Ford designed them for daily driving but we all know most people with a Mustang don't drive "mild," and these things cook fluid. There's no transmission temperature sensor (on the dash cluster) so most people assume it's fine. They'll happily beat the hell out of it without knowing (how would you) that the life of the oil (and other bits) is fleeing. The "sealed 100k mile" thing is horse-____ IMO. At 125k miles, that oil was so dead all the molecules were little caskets. So if the fluid hadn't been changed in all that time and if you were driving it hard, you could also be looking at some burned-up clutches. You'll need candles, a headless chicken, and some ordinary household bleach. :)
Good news is it's not as expensive as an engine.
 

Pentalab

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I can see the 5R55S temperature on my Aeroforce gauges on the A pillar Pod...plugged into the OBD port. You can also see it with an X3 or any thing else that plugs into the OBD port. I can program alarm's in the aeroforce gauges if required.

Sitting in the driveway, eng idling, tranny will eventually get up to 120 F. Before the mods were done, out on the hwy, and cruising at 50-60 mph..... it would sit at 170F.... normal.

However, with gas mashed, and blower on, it would rise from 170 F to 200F in mere seconds. When the 5R55S gets too hot, it will put itself into overdrive....even if you have the OD shut off.

Ok, so in went the various mods + 100% synthetic ATF. Zero issues after that. Now with gas mashed, blower on (5PSI) it will rise from 170F to 171F...and sometimes 172F.

That deeper pan I installed, along with mating (locking type) dipstick, works superb. The dipstick opening is big enough to easily add more ATF if required. The new PA pan has a drain plug on the bottom. However to get it ALL out, we needed to pressurize one side of the Auto tranny cooler..... while using suction on the other side of the tranny cooler.

The catch can had to be installed. Drag racers figured that one out eons ago. Without it, it will puke ATF like crazy. And anybody who drag races with the 5R55S, changes out the ATF on a regular basis...and only use 100% synthetic.
 

JC SSP

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I thought Mercon V was fully synthetic? What fluid did you put in?
 

Autokyrios

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Cool, yeah, I run those gauges, too. PITA user interface, but they work and look decent.
Keep in mind the stock temp sensor is somewhere in the transmission (sorry, can't remember where off the top of my head...it's on the side of the case but where in the flow I can't recall). Anyway, you'll have two temps to watch: temp in the oil galley, and temp at the cooler (mainly this is the temp as it's sent out from the transmission, so at its hottest). My case sensor always reads a good bit below the temp at the cooler, so my guess is it's earlier in the plumbing.
When I first got it and it was fully stock, it would get to 200 no problem, racing or just annoying the floorplate. After that, and a built transmission and TC, I run a custom cooler. Turned the stock auto cooler into a cooler for the steering pump.

In my experience, I'd only stick with the Motorcraft specified fluid. I tried running RP and other brands for a time, and had nothing but issues. I get all the "it's the same" chatter, but hasn't been my experience.
 

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