722.3 early upshifts, no kick down

[babenaldt]

Hey Guys!

Recently I rebuilt the transmission in my R129 SL500 which uses the same or very similar 722.3 transmission as the w124 500e. After installing the transmission I've noticed that when driving it will upshift pretty much as soon as possible no matter the throttle position, and won't kick down when going WOT either. The transmission shifts fine manually, and kicks down fine when actuating the gear lever manually.

I have ensured that the throttle linkage/bowden cable are adjusted properly and checked the functionality of the kick down switch, neither of which have seemed to fix the issue. I do not have an issue with the shift quality, so I don't believe this is a vacuum issue.

Because of this I think that I have isolated the issue to some sort of assembly issue regarding the Bowden cable interface inside the valve body. When manually actuating the bowden cable I have about an inch or so of dead travel and then another inch or so of travel that feels like you're pulling on a spring. The piston in the attached image does not move when manually actuating the bowden cable, which I assume It must. Anyone with more experience with this can confirm that this piston actuates with the bowden cable?

I just thought I would ask for you guys thoughts on this before I embark on the multi hour/day process of removing and reinstalling the bowden cable assembly on the transmission.

 

[gsxr]

Recently I rebuilt the transmission in my R129 SL500 which uses the same or very similar 722.3 transmission as the w124 500e. After installing the transmission I've noticed that when driving it will upshift pretty much as soon as possible no matter the throttle position, and won't kick down when going WOT either. The transmission shifts fine manually, and kicks down fine when actuating the gear lever manually.

I have ensured that the throttle linkage/bowden cable are adjusted properly and checked the functionality of the kick down switch, neither of which have seemed to fix the issue. I do not have an issue with the shift quality, so I don't believe this is a vacuum issue.

Because of this I think that I have isolated the issue to some sort of assembly issue regarding the Bowden cable interface inside the valve body.

Yup, I agree!

When manually actuating the bowden cable I have about an inch or so of dead travel and then another inch or so of travel that feels like you're pulling on a spring. The piston in the attached image does not move when manually actuating the bowden cable, which I assume It must. Anyone with more experience with this can confirm that this piston actuates with the bowden cable?

YES! That should move when you pull on the Bowden cable. Sounds like the cable did not get attached to the linkage rod on the transmission end. This is fiddly even with the transmission on the workbench, and less fun when it's in the car.

I just thought I would ask for you guys thoughts on this before I embark on the multi hour/day process of removing and reinstalling the bowden cable assembly on the transmission.

Yup, you need to remove the Bowden cable from the transmission and get the linkage connected properly. It can be done on the car, but space is limited in that area. Make sure no dirt/debris falls into the hole where it could cause sealing issues with the O-ring (or get into the pan).

 

[babenaldt]

Yup, I agree!




YES! That should move when you pull on the Bowden cable. Sounds like the cable did not get attached to the linkage rod on the transmission end. This is fiddly even with the transmission on the workbench, and less fun when it's in the car.




Yup, you need to remove the Bowden cable from the transmission and get the linkage connected properly. It can be done on the car, but space is limited in that area. Make sure no dirt/debris falls into the hole where it could cause sealing issues with the O-ring (or get into the pan).

Thank you!

I remember spending about an hour or so on the bench trying to get that interfaced correctly, I guess even still I did it wrong.

Now I gotta debate whether or not I should remove the transmission for the third time to fix this or attempt to do it on my back under the car. Luckily winter has started here, and I won't be driving the car for a while regardless. If the trans does come out, there's a non-zero chance a manual will go back in to replace this freshly rebuilt 722.3...