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JayRex - 5EAT Rebuild


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I bit the bullet and opened up the pan. Smoking gun staring right in my face.

Putting it back together in a bit. I'm hopeful this is 100% of my problems. I'm removing the resistor 'hack' too. I was reading up on the manual. Actual trans fluid temp is very important to the TCU... go figure. :redface:



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Okay, things are looking better, but not out of the woods yet.


PRND indicator lights work as they should.

Sport mode works - P1817 code is gone.

Trans temp code is gone - P0712

Accessport is showing Gear Position changing, but I'm not convinced all of my clutch packs are engaging as they should. Might just be because a code was thrown and its in limp mode?


New codes YAY!

P0734 - 4th Gear Incorrect Ratio

Searching shows this could be related to low trans fluid, and I JUST filled it and went for a drive.


P1799 - Interlock

Not a lot of info out there on this.


Fishbone posted about this years ago, but I don't think it really applies because I never had the code before, so a TCU reflash is probably not necessary.



Going to reset and see what happens.

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Did another reset. Short drive. More definitive results.


Will not shift out of 3rd. 4th and 5th are just 3rd gear, but they seem to slip. 3rd gear and lower does not slip. The car will down shift to 2nd and then to 1st.


no codes, but im sure if I drove it more, the code would show.


I guess I should start troubleshooting with a valvebody replacement. This is turning into quite a mess. =(

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The trans might have a little too much fluid actually, need to double check it and adjust.


I don't think its a fail safe issue, just because its acting up without any codes being thrown. I think I have an actual mechanical problem.


I am interested in your VB, I could always resell it if its not the issue.

I can send a prepaid shipping label. Lets chat details over PM.


Found a post with the exact same problem. They get very technical in this thread, interesting reading. Makes me think my Input clutch is not activating, not recieving pressure.


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New codes. I don't know if more codes are a good thing or bad at this point. :p






Showed up within 1 min of starting the car, was just moving up my car ramps to take some trans fluid out. Came on before I started moving up the ramp.

Edited by jayrex
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I guess I can say YES to step 2.

This is really starting to look like an electrical problem. Those last set of codes are most of the clutch solenoids not firing.


EDIT: You are probably wondering why I am looking at code P0736, when I have code P0734.

The FSM points you to P0736 for any of the similar codes.

Codes P0731, P0732, P0733, P0734, P0735 all use the same diagnostic troubleshooting listed under the P0736.

Edited by jayrex
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Reset codes again. About a 10 minute drive with no codes thrown, but the problems are all the same...


Bought whitrzac's VB, I'll see how that goes.

Edited by jayrex
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I just found out you can use the FreeSSM tool to monitor realtime TCU values. Shows max/min, and current value. I drove around until I pulled a code (just the P1799 - Interlock this time). Still cannot go past 3rd.


I'm not 100% sure what I'm looking for, but it looks like all of my solenoids are working. There were no 0's for any of the max values. I'll try to post the screenshots from FreeSSM, those are stuck on the laptop for now.

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You can use romraider logger too.

Good to know! I was thinking a log would be more useful than just max/min.

Graphical? Or would I need to graph it independently?

I need to figure this out before pulling the trans again - pending the VB swap not fixing the issue. Will be working on that this weekend.

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interesting. I didn't realize RR added functionality to connect to TCU for logging ability. I'll have to check that out if I can resurrect my VAG-COM cable and laptop logger. I've been wanting to watch ATF temperature.
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Took a quick look at RomRaider last night. Looks like a more powerful tool than FreeSSM. I think I always ignored it because I was afraid I'd regret spending the money on an AP. lol.


New VB is here - thanks whitrzac! I'll be tinkering with that soon. Going to try and get some before and after logs using RomRaider. Even if the VB swap doesn't solve my problem, at least I can get some data comparing Modified VB vs Stock VB.


Really hoping this solves the problem, otherwise I have some serious work ahead of me... and more $$$ to spend. =/

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Attached a TCU log. I'm not sure if anyone has experience with these. Not really sure what I should be looking for. You can see with the gear changes, that the rpm does not change, just keeps climbing, which is what it feels like in the car. Feels like a CVT trans :lol:


FYI - still my modified VB, not the new to me - used stock one.


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I had a look. Don't like what's happening between 1-2K engine RPM.

Is this where you notice funky behavior now?


The first plot below is 5EAT turbine speeds vs time

The second plot is the same vs engine RPM


I think you should concentrate the solenoid and line pressure checks in this area of logged engine RPM.


For example, check out the odd looking P/L solenoid pressure in that range.

I don't think this has anything to do with pre-TC lockup slip or torque amplification.

I'd think the plot should follow a similar trend from low RPM up to torque converter lockup (2.5, 3K RPM?)


I also don't see any log entries for 3rd gear! Its as if the ECU/TCU couldn't calc/estimate any 3rd gear instances.


The last two plots zoom in on the data captured between 1-2K engine RPM.


The P/L solenoid readings are clearly all over the place (unlike <1K and >2K engine RPM) and the AT turbine speeds per gear look odd.

I don't know how to interpret these, but either 1st gear is fine, 2nd is odd, 3rd missing, 4th fine and 5th fine.

Or 1st is fine, 2nd odd, 3rd missing, 4th fine, 5th fine. I think any transmission shop or one of our 4/5EAT gurus on here might know better.


Seems to me some (2nd/3rd gear?) clutch packs might be going, your TC is slipping and not locking up or both.


BTW, no ATF Temp logged? See if you can add that to the log. Would be good to see.


Also, since your pre-2008 Scoobie can't do SSM-over-CAN I'm assuming you're limited to K-line.

But check if you can check off 'fast polling' (faster K-line requests).

With so few params being logged from the TCU, your polling rate should be better.

Right now we only have ~170-180msec sampling rate. Would be better to get that down below 100msec, or even closer to 60msec if possible.




Edited by Perscitus
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Did you fill the torque converter with ATF prior to install? Assuming you did:


This is binary.

Replace valve body. Pass/fail.

If fail, it's internal to the transmission. You have a good grip on the FSM troubleshooting, which is key. Hopefully pulling it apart reveals a smoking gun. If you find one clutch pack burned up, definitely replace any related seals.

[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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Perscitus, thank you very much for taking the time to graph and check my logs. I appreciate the time spent on that.


Trans was warmed up prior to log, about 150 - 170 deg F, but I will log Temp next time. I will also look into getting better resolution. I am using the KKL cable.

I'd also like to be more methodical with the gear shifts. I actually took two logs, one with normal D, and the second in manual mode. The weird thing is, I only found one log saved. So I don't know if it was added onto the first, or over written. Not sure how RR Logger handles the files. I just clicked 'stop logging' and then a few seconds later clicked 'start logging'. My guess is that they were chained together. I'll figure that out and get a good

1 - 2 - 3 - 4 - 5 - 4 - 3 - 2 - 1 in manual mode.


One other weird thing I just remembered. I think it only activates the manual downshift I requested after I hit the gas a little.


ClimberD, thanks for the input. I actually didn't fill the TC prior - honestly didn't know it was necessary. After extensive googling, it looks like its a 'best practice' type of thing, not necessarily a show stopper. Many people say it fills right up after the pump starts moving.


The first step is definitely changing out that VB. That will certainly get me closer to the cause. I am spending a little time logging before that because I want some good data to reference back to, after I make the swap.


Condition 1- If the OEM VB solves my problems, then I'll have data to hopefully zero in on the issue, and fix the Modified VB. Elevating it from 'paper weight' status :lol:


Condition 2- If the issue remains, maybe I can compare some logs to further reaffirm the problem location in the mechanical bits of the trans. I really don't want to open up the trans again, just to go looking around for a problem. That seems like too much uncertainty for that amount of work.


I think I need to get more familiar with this table to understand where the problem specifically is.



Even when it does seem to be working a little, its not shifting well... very sloppy and 'slam shifty'. Once its settled in gear it does hold very firm, where my previous frictions would let loose under load. Where I am having problems now, I've never had slipping issues, so I don't think its the few lightly worn frictions I left in there.


Anyway, I'll get a few more logs and swap the VB in the next day or two.

Thanks for you help, this would be much harder without any input from others.

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I was looking at the Gear Train Table a little more.


Regardless of the logs... it feels like it shifts up to 3rd, then 4th is the same as 3rd, and then 5th feels like neutral.


See if my logic makes sense.


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Super mad and happy at the same time... that's a weird feeling.


Pulled out my modified VB. I'm thinking this valve needed to be held it by a little more than air... Retainer must have fallen out during re-assembly of the 'slabs'. I can't believe I missed that. I guess I need to work on my 'attention to detail'.



To get it up and running sooner, I put in the unmodded VB. I can test that one, and test the rest of the trans without the complication of the modded VB, and I need some parts that are missing anyway. I don't know where those pieces ended up... quite the mystery. ClimberD is hooking me up with some parts from his spare pile. - Thanks dude!


I have not fired it up yet. Writing this while I get the trans fluid in. Trying not to get too excited, but am really hopeful this will clear up my issues. I will update with the results soon.


Check out my new TRANS-fusion setup. :cool:


Big pan to catch the never ending rain of trans fluid.




2 Gallon bucket with paint strainer screen.




Dirty bits screened out.




TRANS-fusion time! This thing works great - little 1/4" NPT ball valve with brass nipple to some clear 3/8" tubing which fits right down the dipstick tube. Not one stray drip, and you get it done in one shot. (Home Depot plumbing isle)


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  • 1 year later...

Brief followup on this trans build.

I had been using the stock VB for about a year and a half, and it started slipping very bad again, even at about 25% throttle. (19lbs on E85)

I finally repaired the modified VB and installed it without changing the failing frictions. The difference was nothing short of amazing. The VB mod is just incredible, but 6 months later and the slipping is back. My frictions were on borrowed time anyway. I bet I wouldn't have burned up them up if I had the modified VB working from the start. Trans still drives okay, but I just can't punch it on the highway. Waiting for some warmer weather here in New York before I open 'er up again.

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