5R55n shifting problems

dean71

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hey everyone, I want to apologize in advance for this lengthy post.
I have a 2001 3.0 LS with 143000 miles. about 10,000 miles ago, it developed a slip when downshifting to pass at highway speeds. I could let off the gas and it would shift and then it would pull fine. This would happen maybe once or twice a month. I had hooked my scanner up several times and never had a pending code. I read the COPs could be a problem, and I swapped a couple out with no difference. I also cleaned the MAF and throttle body. This continued, but didn't get any worse until recently.
Driving back from town one day, it decided it didn't want to shift to 3rd under normal acceleration. it would slip and duplicate the rev limiter like what it would do in park when giving it gas. Again, letting off the gas would allow it to shift to third. Once in third, it would pull hard and shift to 4th and 5th. Before we got back to the house, the "E" was displayed. I hooked up my scanner and pulled the P0795. I decided to park the car and order a new solenoid pack and some valve body replacement springs. I disconnected the battery cable as I have read the PCM needs to relearn the adaptive shift strategy when replacing transmission parts. I pulled the pan and didn't notice any metal shavings. The fluid wasn't burnt. I replaced several springs in the valve body and noticed the 4-3 spring from Sonax was a bit longer than the stock. I couldn't find any info of anyone having a problem with this, so I used it and continued with the assembly. I installed the valve body, new solenoid pack and replaced the fluid with MerconV. Hooked the battery back up and ran the car to temp and rechecked the fluid. everything seemed fine.
The road test proved everything wasn't fine. not only wasn't it shifting into 3rd, it wasn't shifting into 4th anymore. I decided to try to let the PCM adapt for a few more short drives, but nothing improved. the only way I could get it into third, was to manually select third and I still had to wait for it to shift after letting off the gas. The loss of 4th had me stumped though. back to reading.....
I decided that maybe I had misdiagnosed the loss of 3rd and it may have been a worn servo bore on the intermediate band. that would explain loss of 3rd, but not overdrive. I never had a single slip in 4th and 5th is just overdriven 4th. I decided to pull it all back apart and replace the longer 4-3 spring with the stock. I inspected the valve body gaskets very closely and didn't find a single flaw. I also thought I may have had a bad solenoid pack and replaced that again as well. The next road test was the same result. No 3rd, 4th or 5th.
I'm a diesel mechanic by trade but I don't mess with automatic transmissions very often. I do trust that I assembled everything correctly. So, what do you think my next move should be? I'm thinking about replacing the entire valve body and separator plate with the bonded gaskets and then take it to the dealer to have the PCM re-flashed if that doesn't fix it. I heard the re-flash could take care of the problem, but normally, the transmission would at least shift. I talked to the local Ford dealer and was told they could replace the trans for 3690.00 or rebuild mine for 2500.00+++.I really don't have the time to rebuild this trans and it would be my first one. I'm already tired of throwing parts at it and want to get this thing fixed without shelling out at least 2500.00. Has anyone had this problem? I have read of people losing 4th, 5th and reverse, but not 3rd and then 4th after replacing the solenoid pack and some springs.. Help!
 

joegr

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It could be a bad PCM. Replacing just two of the coils and plugs was foolish, based on the experiences related here and elsewhere. (Marginal coils can be hard to detect, and over time they can damage the PCM, as well as cause damage to the cats.)
 

dean71

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It could be a bad PCM. Replacing just two of the coils and plugs was foolish, based on the experiences related here and elsewhere. (Marginal coils can be hard to detect, and over time they can damage the PCM, as well as cause damage to the cats.)

Sorry, let me clarify. I replaced all of the plugs. I used an HEI tester and replaced two coils which showed to be marginal. I did not have the money to replace all the coils at the time or I would have. Again, I was never able to pull any type of code when the car first started showing the symptoms. I figured I would have had a miss fire code but I didn't. The car passed California smog just 3 weeks before this happened. Thank you for the reply. Are there some threads I am missing which related the experience I am having with a failed PCM?
 

joegr

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Very few of the bad coils that I have experienced ever set any misfire codes.
There are threads here and there about continued transmission problems that were finally solved by replacing the PCM. PCM failure is rare, but it does seem to be more common on the V6 than the V8. Unfortunately, PCM replacement requires towing to the dealer or the use of a high end scan tool to be able to start the car after the replacement. In either case, you're also required to have at least two working or new keys with you.
 

LS4me

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I never had a single slip in 4th and 5th is just overdriven 4th.

Not true for the 5R55N. From the head transmission calibrator for the LS........

The transmission in the LS is really two transmissions in one housing. There is a two speed in front and a three speed in back.

First gear has both the front and rear transmissions in low gear.

Second gear shifts the front transmission to high and leaves the rear transmission in low.

Third shifts the front transmission back to low and the rear to second.

Fourth leaves the front in low and the rear shifts to high. Both front and rear are now in 1:1 ratio.

Fifth shifts the front to high again and leaves the rear in high.

From the above you can see that changing the overdrive ratio (the front transmission) affects second and fifth gears. Changing the rear three speed ratios will change all the ratios except fourth and fifth.
 

Broseph

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Somone correct me if I'm wrong, but doesn't the overdrive servo have something to do with second, fourth and fifth gears? This would definitly fit under this scenerio if it's correct.
 

dean71

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The confusing part of this whole thing is there was 4th and 5th before the new solenod pack was installed and valve body removed and replaced. Although I'm not ruling out a problem with the PCM, I'm still leaning more towards a problem with the valve body and or valve body gasket as the problem. If the overdrive servo bore was losing pressure, I would think I would have noticed it before. I appreciate all the input. I'm just trying to isolate the problem and not have the dealer only tell me the trans needs replaced.
 

Broseph

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The confusing part of this whole thing is there was 4th and 5th before the new solenod pack was installed and valve body removed and replaced. Although I'm not ruling out a problem with the PCM, I'm still leaning more towards a problem with the valve body and or valve body gasket as the problem. If the overdrive servo bore was losing pressure, I would think I would have noticed it before. I appreciate all the input. I'm just trying to isolate the problem and not have the dealer only tell me the trans needs replaced.

From what I gather the issue is four possibilities: valve body, soleniod pack, overdrive servo, PCM.

The solenoid seems unlikely for the symptoms described. PCM, as Joegr and everyone else will tell you, is highly unlikely. Don't discount these as being the culprit though.

So you're looking at valvebody or overdrive as your most likely candidates. If either one of these needs replaced you're well under what the dealer will stick you with, and neither one of those are extremely difficult jobs.

Ask any member, and they will tell you how strong this transmission is. Outside of a few glitchy areas that are well documented now, the gearing part of this transmission is very hard to break.

As always, let us know what you find. Too many times people have problems and never say what fixed it to give others a heads up.
 

dean71

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From what I gather the issue is four possibilities: valve body, soleniod pack, overdrive servo, PCM.

The solenoid seems unlikely for the symptoms described. PCM, as Joegr and everyone else will tell you, is highly unlikely. Don't discount these as being the culprit though.

So you're looking at valvebody or overdrive as your most likely candidates. If either one of these needs replaced you're well under what the dealer will stick you with, and neither one of those are extremely difficult jobs.

Ask any member, and they will tell you how strong this transmission is. Outside of a few glitchy areas that are well documented now, the gearing part of this transmission is very hard to break.

As always, let us know what you find. Too many times people have problems and never say what fixed it to give others a heads up.

I do really appreciate the responses and help. This forum helped me trouble shoot and repair the cooling system a couple of years ago. Unfortunately, my wife and I decided we should trade the LS in. We took a hit being the trans was a mess, but we were able to get into a 2010 328i bmw with 55,000 miles. We both loved the LS, but with as many miles it had on it, we feel we would have ended up spending more than the cars worth if I did end up having to replace the transmission. I too wish some members would post resolutions to their issues. There are far too many dead end posts. I agree the valve body was most likely the culprit is this case. I traded in at the local ford dealer. I will find out if they plan to repair it before they wholesale the car. If they do, I will post my findings so others can benefit from this thread. Thank you again
 

dean71

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Get ready to open up your wallet....... BringMyWallet! Sold by a Ford dealer? Why did BMW wholesale the car?????

The bmw is certified and in perfect condition with flawless service records. I have had 3 BMWs in my life and haven't had any more trouble out of them than any other make I've owned. One of my BMWs had over 315,000 miles. The dealer said they were most likely going to sell the LS we traded in wholesale. As far as my wallet...I have spent more on my LS in the last three years than the last two BMWs combined. :-\
 

lking

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It could be a bad PCM. Replacing just two of the coils and plugs was foolish, based on the experiences related here and elsewhere. (Marginal coils can be hard to detect, and over time they can damage the PCM, as well as cause damage to the cats.)

so you were saying here that even tho there is no sign that a coil pack is not working properly it can still damage the pcm and cats?

I had one bad coilpack a while ago i changed it and all six spark plugs cars been idling fine ever since...maybe the other five coilpacks which show no signs of damage caused my PCM to go bad? also my cat does smell bad from time to time
 

joegr

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so you were saying here that even tho there is no sign that a coil pack is not working properly it can still damage the pcm and cats?

I had one bad coilpack a while ago i changed it and all six spark plugs cars been idling fine ever since...maybe the other five coilpacks which show no signs of damage caused my PCM to go bad? also my cat does smell bad from time to time

Not everyone is good at detecting the infrequent and slight misfire from marginal coils. However, if your PCM were damaged by a coil, I would expect that you would then be able to detect the misfire caused by the bad PCM. I think the PCM failures are rare, but I have heard of more V6 LS PCMs failing than V8 LSes. However, I don't know of any particular reason as to why this would be true.
 

jjcool00

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What makes you think the PCM has gone bad? The failing cat is a definite possibility as I can attest to it personally happening to me. It caused terrible performance related issues (delay when hitting the gas pedal, loss of power, etc.) As soon as I put in new cats, it was a world of difference.
 

lking

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What makes you think the PCM has gone bad? The failing cat is a definite possibility as I can attest to it personally happening to me. It caused terrible performance related issues (delay when hitting the gas pedal, loss of power, etc.) As soon as I put in new cats, it was a world of difference.

is that question for me? the person that started this thread bought a BMW and has moved on long ago...

i think my pcm is the problem because i have changed my solenoid pack TWICE and i still have harsh shifts

the thing is all the symptoms i have and have had are failing solenoid pack symptoms usually when a PCM is bad or something else there are other symptoms

symptoms i have are

kicks into R and D from P or any other gear harsh shifts when in drive mostly gear 1 2 3
 

jjcool00

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Yes that was for you... the clogged cat caused serious hesitation issues when I had it, but not harsh shifts.
 

lking

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I've never had hesitation issues except for when the rear wheels lose traction in snow
 

lking

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It could be a bad PCM. Replacing just two of the coils and plugs was foolish, based on the experiences related here and elsewhere. (Marginal coils can be hard to detect, and over time they can damage the PCM, as well as cause damage to the cats.)

how does a bad coil pack damage a PCM?
 

joegr

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how does a bad coil pack damage a PCM?

High voltage/high current spikes from the primary of the bad coil can kill the transistors in the PCM that drive the coils.
 

DaveLS

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symptoms i have are

kicks into R and D from P or any other gear harsh shifts when in drive mostly gear 1 2 3
I have really similar problems with my transmission (I have a 04 LS v6). How can I fix my PCM?? I rather start by seeing if my PCM is the problem and if it's not, replace the solenoid pack and do a fluid flush
 

lking

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I have really similar problems with my transmission (I have a 04 LS v6). How can I fix my PCM?? I rather start by seeing if my PCM is the problem and if it's not, replace the solenoid pack and do a fluid flush

could be either one or both who knows the only way to determine is by replacing

damaged solenoid does not throw any codes neither does a PCM although sometimes damaged PCM is obvious if not you'll only know by replacing it and these parts are not cheap

you should change the solenoid pack first since that is the more likely to be damaged do a complete fluid flush while your at it the 04 LS left the factory with "bad" fluid which is why your solenoid pack might be damaged no sense in replacing the solenoid pack if your not going to change the fluid 100%
 

lking

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High voltage/high current spikes from the primary of the bad coil can kill the transistors in the PCM that drive the coils.


so can a damaged solenoid pack damage the PCM? damaged solenoid pack kill the transistors in the PCM that drive the solenoid?
 

joegr

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so can a damaged solenoid pack damage the PCM? damaged solenoid pack kill the transistors in the PCM that drive the solenoid?

Not as I have heard of. I suppose it can't be ruled out. Most often, the failures with the solenoid assembly are mechanical, which couldn't cause any harm to the PCM.
 

lking

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