i also have the hunt and was wondering if paul had found anything else. i am a little skeptical just because when i recoded mine to sport mode the hunting went away for 2 weeks and gradually returned. probably because it reset the adaptations in the process. has anyone ever replaced the transmission control module? im sure they are not cheap but this sure seems like a software issue to me. thanks for the help!!

 

Well, With the replacement TPI, and a genera disconnect and remake of all the connectors in the TCU/ECU box under hood. ThHe hunting in this vehicle "Changed" signifacantly and has now returned pretty much the same. Now I wonder if it is I who is being trained not the TCM?

With a 300 mile I-91 ride early sunday morning, The transmission is pretty easy to live with, but wouldn't you know it, the "hunt" still happens right at 75 mph/ 2000RPM in 5th. perhaps 50 RPM hunting, barely noticed, and only accasionally.

I've been pouring over logs on transmission events trying to correlate shift events, solenoid status, engine load, TPI, etc etc.

I have some observations, but no conclusions.

I di make a purchase of both and ECU and a TCU at a good price. "Just to try" When they arrive, I will do a swap out and log the data. Unless there is a weakness in the 5-Volt sensor signal supply, I don't feel a replacement unit will change much. I wait to see.

Also, there is an exchange in progress regarding Valve body "differences" between the DTE transmissions, and later versions. This might be good. TOZOM8 Is the positive experience leader here, but we don't really know what was the change that displaced the hunt.

So, from my experience, The TPI is not a sure thing (Unless I got a bad one ;-()

CalG

 

However, the TC still drops out on the highway.

I would imagine it has had time to learn, but don't know for sure without a few more weeks under my belt.

I have never had TC hunting on the highway unless I lifted on the gas and it dropped out.

I have a spare 98 TCU and have swapped them out....also running a 98 ECU in my car and neither of them changed anything for me.

I will continue to monitor.

I also wondered if I had a slight air leak around the TPS, I did change the gasket with it....but that should result in a long term lean code which I have never got.

 

Unless I made a mistake correlating valve shapes and locations from your Dec 28 2006 posting, the WK-V valve which sends lockup pressure to the converter clutch lost a hole in its 55.010 Valve Housing.

And you're entirely right that we don't know if the change helps prevent hunting, or if tozoM8 simply benefited from using a valve body with less wear. Somebody at ZF knows.

Tom

 

to spew a stream

What I have from a recent phone conversation with US Bosch Transmission devision is that 70% of the transmission function is determined by the Customer (read Audi/VW) software. 30% by the Bosch firmware coupled to the transmission hardware. Software could overcome many deficencies. My reading suggest "Flash upgrades" provided by other manufacturers can provide drivability enhancement. These Bosch TCU's are "flash capable" though Audi offers no assistance here, too bad. I read that BMW and M-B are no better.
Even Bosch has a difficult time to get a copy of such manufacturer's software when it comes time to performance test their end. I look for software solutions, just because.... Unfortunately, I am an optical and thin film engineer ;-( not a programmer or device designer. How do the aftermarket "chip" vendors get the inside information anyway?

Speaking with the ZF authorized service center contact, There are differences between the model years noted, but the reason or effect of the change is not understood....yet.

I am trying to "assist" with this understanding.

To do this, your useful explanations, and the photos from TOZOM8 are most helpful.

I have challenged the performance associated with the TCC circuit, ports and the accumulator, but that was not explained.

The $750 toll for the ZF Valve body service book is looking attractive just now.

But, In the back ground, my mind clings to the control system. The data logs show the transmission to obediently following orders from the TCU. The only idea that has formed in my brain thus far is that if the VB can act as a timing and event sequence control via port configuration and accumulator, then the ECM/TCM can sample and respond rapidly (desired) while not over responding (Undesired and as per your analogy of steering etc.) I must always remember that the entire transmission depends on the artful combination of supply pressure and flow, mechanical actuation, hence volumn, and controled out flow. Many delicate balances come to play, and the fluid needs to do several important task simultainiously.

All the sudden, $3k doen't sound like enough for one of these units.


IF the TCM is programmed to provide economy, but that programming is in conflict with changing values or sensor signals, wouldn't an adjustment to the control algorithm be a logical alternative? I'm thinking just defeat the Economy mode and move everything up a notch.



That said.
At 100K miles
With the TC gathering debris over the miles,
the clutch packs nearing the end of their service life (depending on driving history, urban vs highway)
The possibility of a simple seal failing and the idea that even the spring in the line pressure control regulator could be going soft. All add up to support a complete transmission rebuild.

That being said!. I wadger to easily get an additional two years and 50K miles out of this unit. It will just **** me off every time it cycles through the hunt.

 

I'm sure we will all be waiting for your "TPS report" ; - p

 

Depending on what's wrong, even the best possible software might not be able to get the converter clutch back under control.

We don't yet know what's wrong. When Paul's car suddenly started hunting one day, it probably wasn't the software which had changed overnight. Sure, one can imagine better TCM software might work around the problem (or might not be able to, depending on the underlying cause), but until something happened one day, the stock software was good enough.

By all means, cling to a systems approach. The system involved in a hunting cycle might involve sensors, the TCM and ECM, electrically controlled hydraulic valves, hydraulically controlled hydraulic valves, the converter clutch, the mass of the car, varying engine output at different rpm, etc.

I think everybody who has looked into it accepts that the TCM commands the slip changes during hunting. Such TCM behavior proves only that the TCM's not programmed to break the cycle by, say, leaving the clutch unlocked. It suggests that whatever lets the hunting develop was not originally envisioned as possible by ZF (or maybe Bosch, if the problem lies outside the transmission). If they had thought it was possible, they'd have engineered around it.

At this stage I think it's going to be easier to identify and replace the degraded parts than to disassemble the TCM software, rewrite the TCC bits, validate the changes, etc.

Tom

 

No TPS cover sheet!

<img src="http://partyends.com/other%20pictures/office_space_pic%5B3%5D.jpg">

 

sounds fair to me, i guess what i meant was a problem with the tcm software such as when a module goes bad it often behaves erraticly. you are right when you say the software didnt change overnight but it sure seems connected to the tcm. it very well could be trying to compensate for a degraded part it just seems odd that whenever we readapt or recode them (i am assuming paul did also when he replaced his tps) the hunting dissapears for sometime...

 

Tom

I share your views. The hardware can be readily exchanged. The interest now is to know just which element is the straw that breaks the camels back.
Without the understanding and the equipment to modify an EPROM (Or worse a PROM) The Control might remain an unatainable goal. I am curious to know the possibilities, but have not yet come across the knowledge and interest in one person.


Unfortunately there are confliction reports of success and failure with exchange of the same component. Such unrobustness that any one element can push the system into chaos? or not!

I would like to think that the TCC is the weakness. That some change in the friction material due to wear or use, renders the slip uncontrolable with "normal" fluid flow and pressure. Perhaps leakage past the center shaft seal results in less apply force than designed for. Not knowing the limits of the fluid adaptation for such variations, there is a dead end. But fault points to some other system of control when a TC has been exchanged without improvement.

I would like to think that the flow rates or leak rates within the Valve Body may change with age. An obstructed passage or screen somewhere? A softened or collapsed spring in a valve or the accumulator? A "new" VB may answer, but certainly it is not the entire VB. Or is it? Many drops make an Ocean. Again, exchanges have been made both good and bad.

I would like to think that the shifting sequence is distrubed?
The changing response from one of many sensors or actuators?
The wearing of clutch packs, or one of the engagement circuits taking too long to complete a transition, and so triggers the control to abort the present action in favor of a recovery. This would be rectified with a normal "Transmission rebuild" as new metal and friction elements restored the lost distance of the aged elements. Less distance requires less time. hmm..... Pressure and flow adaptation should overcome this. Are we out of range?

I fully equiped transmission shop with a dynometer and test set up could be pressed to put one of these "defective" transmissions to task. Analyzed performance will showing the the problem. The truth would come out rapidly.

We try as laymen with the tools available to us.
We Co-operate and confer


Time and money
A friend is needed. ;-)



CalG