Transmission Shuddering

[gamefanatic]

Having troubles with the transmission. I have been watching it for a while now, and until recently I couldn't put my finger on what I was experiencing. Now it's more evident that the issues are coming from the transmission and not an un-monitored miss-fire, which I still believe is occuring.
When traveling in 3rd or 4th gear under light to medium throttle the transmission shudders. Watching the TCSlip on my Torque app I can see this is happening only during an unlock condition.
I have tried to increase the TP (Transmission Pressure) for shifts in my TweeCer, but haven't been able to find values that may relate to the TP after the shift.
At any rate I believe this to mean that the Torque Converter is going out at 140K of hard life driving. Not upset about it at all, just looking to get it to last a bit longer before doing a full replacement. Any ideas?

 

[gamefanatic]

One other thing to note. In the locked up scenario the shuddering goes away, so if there were some tweecer values that would help to hold the lock up under higher loads, that may help too. I just don't know if I have them available to me. Might need to reach out to TweeCer guru's for help there.

 

[99sho-time]

I remember doing it uphill even on slight uphill before mine went out. I don't know enough to pinpoint what it could be but i'd say it's the torque converter slipping on the shaft

 

[gamefanatic]

In this case the shuddering is felt when going in to lockup. So this is likely the TC clutches starting to slip. However, I can't rule out the TCC solenoid failing. I just haven't taken the time to validate the transpressures during the lockup scenario. I need to do that to ensure what I am doing in the tweecer is making any effect.
I have done the basic driveway tests on the pressures, and everything is about right. TC stall about 2300rpm. So another reason I need to check up on the TCC solenoid.

 

[GEN 3 SHO FAN]

Before going into the trans... Do you still have your factory gas pump ?

I know that I spoke about that at soem others places but they aren't trustable above 130k (replaced at 133k on SHO and 155k on SLO) and you are at 140k.

What you felt seems very close to what I experienced with mine (at low/medium throttle on highway) and it was the gas pump not giving enough fuel to motor (they lose power over time rather than stop working). The computer try to monitor this but this gave very bad behavior to the trans. TC will lock and unlock, no kickdown when asked, just unlock and return to same gear as before. The prob will be worst over time at the point you will have not enought power to pass a car on highway speed. With my new pump in place, trans acting flawlessly again.

This bug isn't always visible at idle, you have to take the gas pressure under load when driving. (Thanks again for the trick Mr Nimz.)

I suspect that many SHOs (and probably SLOs) gone to scrapyard because owners and probably their mechanics thought the trans was going away...

Keep us informed.

 

[gamefanatic]

Yeah, I had been diagnosing some fuel pressure issues last year and replaced the stock pump with a TRE-342 255lph pump and replaced the stock regulator getting my running pressures back up to specs.

The way I am able to tell the issue is with the transmission is by monitoring the TCSlip. I haven't gotten a PID that actually reports the TC is locked or something that could monitor the volts of the TCC solednoid as of yet, which would be better options. So, while its not an exact science, I can pretty much tell when the slip numbers get into the low hundreds, that the TC is locking up and conversly when the TCSlip goes into high numbers that its unlocked. Its when its transitioning to the lockup is also when I start to get the shudder.

I was able to rig the tansmission TC un/lockup to not lock up until higher shift points, but once locked it wants to come out due to load factors. Thats the part I haven't figured out how to control.

With my trans cooler, I rarely hit 200°F even in the heat of the summer, so it would work just as well for me to keep the TC from locking. Though, I'd prefer to force it into lockup and not come out. This would avoid heating up the trans fluid and maintain fuel economy on the highway.

Once the weather starts heating up the A/C is also going to wreak havock when it kicks on and off.... ** hum. I have another torque converter from a 2004 AX4N. Not sure if there would be any compatibility issues, but its seems like it should work.

 

[stephen newberg]

For what it might be worth, I am at well over 200k now and still no transmission issues at all.

pax, smn

 

[GEN 3 SHO FAN]

Gamefanatic is right about A/C however. When the A/C clutch goes on, the TC unlock each time for a second. Over time, it's not really good for the trans. My A/C is long time dead (maybe it preserved the trans then).

I'm not very good with trans but I put a Lucas trans fix bottle in mine and that helping resolving some little troubles into mine (hard shifts) after a couple of days.

Had you try to run the car without A/C just to see the behavior of the trans ? (unplug the fuse or the pressure switch near the compressor)

 

[gamefanatic]

Well, with the current weather conditions A/C isn't a nessesity. For now I turn it on for defogging, and once for cooling. It was that one time that I realized how much trouble it will cause in the comming weeks...

 

[99sho-time]

I noticed that even when i put my heat on the clutch kicks on and off I dont know why. Not when I have just the upper vents on, but if I switch it to heat to where my feet and upper vents at same time it does it it also kicks the cluth on and off when I defrost my windshield.

 

[stephen newberg]

That will happen any time the climate control system is engaged, regardless of positions except for in 'vent'. That is the only position that disengages the system completely.

pax, smn

 

[gamefanatic]

Actually vent and floor only. The rest will engauge engauge the A/C purely for dehumidification, IE) defogging.

 

[stephen newberg]

Floor too? Are you sure? I thought it was vent only, but might be wrong. In floor does the system not allow heating also? If so, it goes through the entire climate system so as to remove moisture from the air, so you would still be getting the clutch to engage and drop out regularly.

pax, smn

 

[gamefanatic]

I'm positive there is no clutch engagement on either of my SHO's.

However, the the floor / dash option does engage the A/C in order to defog the windshield.

 

[stephen newberg]

Interesting. I will have to try it on mine. I know that the floor/dash one does. I will have to check on mine for the 'floor only'.

pax, smn

 

[gamefanatic]

I'd be interested to know if it was different.

 

[gamefanatic]

I did obtain a new tool from Amazon and downloaded the FORScan tool which does allow monitoring of most all the things I have been wanting access too!

Its not real time, but can get near half second updates, which is good enough for what I need at the moment.

OHP Ford ELMconfig USB device

 

[stephen newberg]

I'd be interested to know if it was different.

Yes, now you have me wondering too. I suppose I could be remembering it wrong. The problem, of course, is I have no easy way to check. The AC died years ago now, and as this is Canada, I have not really had any good reason to pony up the dollars to get it fixed, so I am working on memory alone.

pax, smn

 

[98SF19]

I began a new thread with an A/C focus . . .
https://shoforum.com/index.php?threads/reviving-the-quest-for-a-c.137308/

 

[gamefanatic]

Well I haven't been able to find a scalar or function that would control the hysteresis of the unlock as of yet, but I was able to basically stop the lockups from occurring. Basically what I did was change low speed lockups to a higher speed. This effectively stops the transmission from attempting to lockup. Below show the changes I made. The yellow highlights represent the differences from the stock settings.

3rd Lock


3rd UnLock


4th Lock


4th UnLock



Now lockup in 4th wont start until about 83mph. Just as a note I did change the mph of the 7th column in the 4th lockup to 85mph..
As one would expect my MPG has been hit a bit. Though I haven't run it through more than a tank of gas, but I'd say I have lost about one mpg.