RPM surge ?

[MercedesTech]

On cruise, the converter stays locked !

Converter unlocking during decel (ie. foot off the pedal) or when quicly accelerating (pressing down quickly on the throttle) is normal. However if the converter keeps locking and unlocking while at a steady cruise, there is a problem.

Hmm.... Because no matter what speed, it unlocks immediately. Doesn't feel right, but maybe just me looking for something wrong.

Anyways, yes, the converter will lock and unlock under steady acceleration. The RPMS also bounce around. when it first goes into 4th. I will feel the surge. While under steady pedal, I will feel the RPMs go up, and the truck pull (talking only a second) then drop right back down and feel slugish, then shoot back up and pull, etc. Maybe I should hook up a video camera on my guages so you can see whats happening. Sure is hard driving, and trying to stare at 8+ guages !


Jack&Janet: don't worry about hijack at all. The more the better ! Really.

[kokopellimotorsports]

Subscribed.

Ty

[MercedesTech]

OK, this thing is sporadic at best. Trying to be able to give you details is hard. 3rd gear, everything is fine. 3rd gear, converter locked, rpms bounce around slightly, nothing bad. If its at 1800 rpm in 3rd, when it shifts to 4th it shoots up to 2400-2500 rpm. Then calms down. While in fourth, it will bounce between 1400 rpms, and 2300 RPMs pretty consistantly. During my drive on sunday, it jumped up to over 3k, then back down around 1900. When it jumps up, you can feel the engine pull, and you go faster. So, its not "dry revving" but fully engaged and still revving up.

I dropped timing -2, also tried -1 neither seemed to help at all.

Shudder is still there.

[88Racing]

Don't want to have to mention this, but have you tried it with the STOCK program?

Just trying to eliminate weather its the tune or the tq converter.

Lars

[Jackpine]

That's got to be awful! I hope you and Bill can get this figured out soon. It DOES sort of sound like a TC that can't get itself locked up, doesn't it?

You say there's little RPM bounce in third? Is this with the OD locked out? And, is the TC locking properly here? (Sorry, I just went back and saw that you said it seemed "almost fine" in this condition in a previous post). But, that bothers me too. "Almost fine" is not good enough in my book.

So, this really sounds like a transmission problem, doesn't it?

And now I see that Lars has jumped in with a "perfect" question. If it runs fine in stock, the problem's with the tune, not the transmission.

- Jack

[MercedesTech]

First thing I thought too, but it doesn't seem to be the tunes at all. I have run my 87 econ tune, and my 91 tow tune, along with stock tunes, nothing changes.

Yes, the little bounce was with OD locked out. Its pretty much how I drive my truck right now, jump in a turn OD off. There is a little bounce, but I didn't write those numbers down, so I will have to double check. You don't feel it like you do in 4th, thats for sure. I will get more numbers tonight, or tomorrow.

I think its something with the trans, but really not sure. Next step, is to undo the gotts mod. Not sure if I mentioned it already, but right before this starting happening, I did the gotts mod and a drop in K&N filter. I doubt this is the cause, but will take seconds to "undo" and test out.

Thanks for the help guys, keep the ideas coming !

[MercedesTech]

update:

Trans is TOAST !! Gone !

Today driving to work, it was acting up more then usualy. Slipping more then I have ever felt. While driving back from a parts run, it slipped into nuetral, RPMS SHOT through the roof, and after that, only able to run in 1st gear, with some god awful noise. Reverse kinda work, but again, go awful noise.

Only code I got before this happened were:

P2106 Thottle Actuator Control System

P0720 Output Shaft Speed Sensor Circuit.

Looks like I am in the market for a new trans. Any aftermarket, beefy suggestions ????

Thanks for all the help leading up to this guys.

Oh, and trans fluid is clean as a whistle !


- James

[Jackpine]

Not much help, were we, James? Boy, I'm sorry for this to happen to you.

Anytime I hear about transmission problems, I get all nervous. Back in the 50's and early 60's, if you killed a transmission, you were best off just getting a new vehicle. No repair seemed to make it right. I thought finally we were getting to an era of more reliable transmissions. Maybe not?

I still wish my truck had a manual shift!

- Jack

[JWBFX4]

Wow man that sucks Hope you can get your ride back on the road soon.

[88Racing]

Wow! That bites!

Sounds like something mechanical broke inside?
Pump?
If the fluid was clean the clutch bands should still be good.
You could go new and get the mfg warranty but $$$$
Or a reman with slightly less warranty.

Or tear it down and get it rebuilt with beefy parts.

Of the 3 I have had the best luck with the brand new one. You could also find a performance tranny shop and see what they have to offer?

Lars

PS Pull the pan to see what's in the bottom