Problem with brand new 4R70W. - TCCoA Forums
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post #1 of 6 (permalink) Old 08-21-2006, 12:14 PM Thread Starter
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Problem with brand new 4R70W.

Transmission is in a 95 Supercoupe. it has an Art Carr converter and the transmission was built and installed by Darrin.

On the drive home from Indiana the owner noticed that it shifted funky and converter lockup was goofy. It's been almost a year since the tranny was built and installed but the car has extremely few miles on it. Basically the guy drove it home to Chicago from Indiana and parked it. The customer can't really specify what the problems were anymore because it was almost a year ago, but he called Darrin and at the time he said the funky shifting was due to it needing the proper transmission tune.

Problems were dismissed and the car came to Ohio for engine work. I drove the car from Chicago to Ohio and noticed along the way the converter lock up was irratic and the car seemed to surge under WOT. Didn't worry about it too much because I figured it just needed a good chip and it would be fine.

When I got it here to Ohio we put it on the dyno to get a baseline pull before engine work began. On the dyno the converter was locking and unlocking irratically producing a very distorted graph. The motor was also running like crap so again, we didn't worry about it.

Now with a good motor in the car and a LOT of tuning and experimenting with various settings (from stock to SCT standard files to my own files, to other files by known tuners) and the thing is getting worse. In order to dyno tune the car we had to command the converter open because it won't stay locked up under load.

In fact, it will randomly unlock under cruise as well. I've datalogged the motor running along at 2000rpm and the converter will unlock for maybe .5 sec causing a little rpm spike and then it goes back to normal. Sometimes it will flare after a shift, sometimes it will do a little "shuffle" between gears where it locks /unlocks /locks again.

After the final tuning session for the motor, now it has started shuddering as you come to a complete stop, and will often shuddter as you begin to accelerate again from being stopped. Something is really wrong, but I dont' know enough about these trannies to even start guessing. The fluid is full just as Darrin filled it when he installed it.

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post #2 of 6 (permalink) Old 08-21-2006, 10:14 PM
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I know which car this is because I have only done one of these. I can tell you that it drove fine when it left my place as far as I knew and this is absolutely the first I have ever heard about it. The shift schedule did need to be adjusted due to the modified valve body lowering the shift points and I told him that at the time and offered to do it for him then. He said he had some deal worked out with you on that and said you could do it when you tuned it. I noticed no problems like the ones that you are speaking of here.
But I need to ask why would I ever let a car leave with a problem like that? It makes no sense at all. That would be just plain stupid on my behalf and anyone that has ever had anything installed by me personally knows that I would never, ever let anything like that happen. I have the customer drive the car when I am done and I ask them repeatedly if there is anything they don't like or that needs to change or be corrected. I am not done until I get their ok. When we drove his car the first time after the install we noticed a clunk and that was due to loose flange bolts on the driveshaft. I missed that but straightened it up and we drove it again. I didn't notice anything like this then and as I said, this is the first I have heard of it.
More importantly, how come nobody EVER bothered to talk to me about this instead of me finding out about it in a post about a transmission problem that honestly doesn't sound like a transmission problem from the info provided?
My concern is that if you are seeing an unlock on the datalog then then you are only reading what it is being commanded to do. The computer cannot read backwards because it doesn't have a feedback loop to read lock and unlock. Thus, if you are seeing an honest unlock condition then it is being told to unlock by the software and the tune needs to be corrected to eliminate it.
If you are dealing with that unlock flare going into overdrive there is absolutely nothing you can do to correct this on a modified transmission. They all do it.
Other than that it really sounds like the tune needs to get the proper base N/V set and then get the lock/unlock schedules set right.
If you are not seeing an unlock condition then the converter clutch is likely slipping.
What cooler does he have? I don't remember. The shudder sounds like a converter issue, but I have also seen this when a guy that didn't know what he was doing attempted to tune the transmission on a dyno and burnt it up. I know that you know better than to ever do that though.

But for future reference, I do have a phone and that would have been the best place to start. I could have given so much more immediate help with one simple phone call. It always just makes ones day to read about a problem that you had no idea about and that may not at all be realted to you in the forums. I know that everyone that deals with service in any way just loves when that happens.


Edit: After rereading what you wrote it sounds like you are seeing converter slippage due to an inadequate single disk converter and a burnt up converter clutch. That completely explains the WOT surge and dyno spikes. An overheated and burnt up clutch will also cause the shudder you are seeing elsewhere.
I hate to think that a converter got burnt up in that transmission. It could toast it as well.
That single disk converter with a paper clutch should never be locked up at WOT. Alan knows a lot more about this than I do. He can tell you all about it.

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Last edited by Darrin; 08-21-2006 at 11:10 PM.
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post #3 of 6 (permalink) Old 08-21-2006, 10:18 PM
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post #4 of 6 (permalink) Old 08-21-2006, 11:08 PM Thread Starter
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Sorry Darrin, don't have your # or email. If you could pm it to me that would be nice. This is not a ***** post it's a genuine attempt to find the solution to a problem.

The cooler is whatever you installed. It seems a decent size to me but I'm no automatic transmission expert. This thing acts pretty much the same hot or cold so I don't think it's a tranny cooler problem.

The reason you haven't heard anything about it yet is because the car hasn't been driven yet. Seriously, the guy drove it home and parked it. I drove it to Ohio and parked it again. I just got it back on the road this week.
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post #5 of 6 (permalink) Old 08-21-2006, 11:33 PM
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I mentioned the cooler to Darrin because I have seen many issues where a plugged cooler can cause serious converter issues because the flow is dependant on cooler flow.
I know for a fact that the Art Carr converters are Precision industy single plate units. Darrin does not recall putting an Art Carr converter in that car. Did he put it in or was it installed after the transmission left his house? He and I usually talk about these issues and I would have informed him that was in fact a "pi" singleplate and it states directly on their site Http:// under stallion you will find this note
Directly from
***Note the multi-disc converters are a MUST for applications that are locking-up the torque converter under WOT.
I personally would like to see this issue resolved as I consider both of you to be friends of mine. We are both out of town this week,but I will contact you when I get back. It appears the only way we would ever be able to really fix this would be to get the car to myself or Darrin for proper diagnosis. Diagnosing a transmission on the phone or internet is nearly impossible.

I have to wonder why the customer would not try to resolve a warranty issue himself if thats what he thinks it is. We know Jim has Darrin's phone number.

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post #6 of 6 (permalink) Old 08-22-2006, 09:14 AM Thread Starter
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Just re-read Darrin's post. I think the converter probably is toast.
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