What activates/controls/holds OverDrive?

[EL SHO]

First of all I'd like to wish to you all a Happy New year, full of health and many more SHOs and projects to begin and complete! :sun:

Now.. since I've had my SHO for almost two years I want to really understand how the Overdrive system works in my ATX.

For the time that I've had this car, the O/D will engage but it will not last even 30 seconds and it will disengage automatically until you come to a full stop, accelerate and will do the same stuff over again.

All other gears are fine.

In Nov 2010 I had the trans rebuilt, supposedly all the clutches, bands and TC where replaced along with the valvebody solenoids.
I've also replaced along the way the TPS and NSS, but not the VSS. Sometimes I get the O/D OFF light and the trans will shift rough, but once I reset the code (628) everything goes back to smooth operation.

What is that holds O/D engaged?

I'd like to go in deeper this year (God's will first) and try to solve this O/D mistery once and for all. I've probably asked this before, but maybe not used the correct questions neither I had the knowledge that I now have with my SHO.

 

[SHOtimer]

Did this OD problem start after the rebuild or was it present before and after?

The OD is controlled by the PCM, through electronic solenoids in the transmission, and you of course have the lockout button option on the shift lever.

Doug

 

[rubydist]

628 says excessive slip in the torque converter lockup clutch.

was the torque converter changed when the trans was rebuilt? if not, it should have been. if so, you should check to see if it is still under warranty.

in either case, to solve your problem you need to replace or rebuild the torque converter.

 

[hawkeye18]

There are two different things, both of which can be confused with O/D...

O/D simply refers to 4th gear. What I think you're referring to is the torque converter lockup. That is, as alluded to above, controlled by the Lock-Up Solenoid (LUS) and actually done by the lock-up clutch, which is inside the torque converter. Basically it locks the two halves of the torque converter so you're not losing power in the fluid coupling.

I think you need a new torque converter, personally. Unfortunately, that involves removing the trans.

 

[EL SHO]

This problem was present before and after the trans was rebuilt. I got it rebuilt because of this and other issues that the trans had, but this O/D thing is still present.

I no longer live close to where the I took the car to get the trans rebuilt, but I was told that the Torque Converter was also replaced along with the solenoids in the valve body.

Hawkeye,

You hit the nail, that's what I'm talking about. My car shifts through all 4 gears, the torque converter lockup comes in at around 40MPH and is the one that disengages soon after.
So then it all points out to be the TC. I had the idea that there could be some sort of internal leakeage that wouldn't apply sufficient pressure for the TC to remain engaged.

Does the valvebody has something to do with the TC ?

 

[hawkeye18]

The Lock-Up Solenoid (LUS) - or in the case of all '92+ vehicles, the Modulated LUS (MLUS), is indeed in the valve body - and not only that, all the valving and pistons for the converter clutch are in the valve body. If you want, I can scan and upload the relevant pages from the ATSG guide - but it'll be tomorrow at the earliest.

 

[EL SHO]

The Lock-Up Solenoid (LUS) - or in the case of all '92+ vehicles, the Modulated LUS (MLUS), is indeed in the valve body - and not only that, all the valving and pistons for the converter clutch are in the valve body. If you want, I can scan and upload the relevant pages from the ATSG guide - but it'll be tomorrow at the earliest.

No hurry man, but yea... I would really appreciate those pages, thanks a lot!

 

[hawkeye18]

 

[EL SHO]

Whoa.. that's really good info there!

Thanks hawkeye, this will sure help me down the road on fixing this OD / TC issue.

All I need now is to save some cash... this "getting married" thing is draining me cashflow!

 

[rubydist]

you think you're broke now - wait till she can sign checks from your account!!