722.3 Transmission problem won't upshift to 4 - PeachParts Mercedes-Benz Forum

jshadows · #1 12-22-2006, 07:55 PM

Hi

A while back I posted a problem regarding no reverse gear. I finally got around to pulling the transmission off and trying to fix the problem. Found the problem (broken springs on pressure plate) and repaired that plus replaced the b3 friction discs.

Put it back together bolted it back up and tested it out.

Reverse works great, engagement in R and D is perfect.

My problem now is I can't shift into 4th gear. It goes from 1-2 real smooth and 2-3 real smooth but I can wind it up to 4000 rpm and still won't shift and when I let off it just engine brakes.

The car is my 350SDL and the transmission is a 722.361.

Can anyone think of an obvious culprit considering the fresh rebuild? No other clutch packs were touched, I didn't pull the planetary gears or K2 though all pistons, governor, aux. pump were pulled an reinstalled. Valve bodies were removed too.

I'm desperate here and am at a loss for where to look

Any help would be enormously appreciated.

Cheers

Bob

Gilly · #2 12-23-2006, 09:52 AM

Looking over the info that I have, it seems pretty simple to get that shift and nothing in the bulletins I have that point to this specific problem, so looking at it from a "back to basics" standpoint I'd check the fluid level and TV cable adjustment, other than that possibly something is keeping command valve 3-4 from moving or some weird governor problem. The only thing that needs to happen on this shift is apply K2 and I think the release of band B2.
Gilly

jshadows · #3 12-23-2006, 10:10 AM

Ok..need to revise my post.

Sticking seems to be at 2-3 shift, once I can get to 3 getting to 4 is not a problem.

That leads me to think something wrong in the K1 pack, B1 piston or valve body problem.

Sure would like it to be the valve body at this point since the other 2 require pulling the transmission....again.

Gilly · #4 12-23-2006, 10:25 AM

Unless a true tranny goo-roo has an opinion, yeah I'd switch to the 2-3 command valve sticking. As far as a trans component itself I'd agree on K1, which you're "deep in the bowels of the ship" to correct that.
Gilly

jshadows · #5 12-23-2006, 11:25 AM

Yeah...worse thing is I was inside the bowels and didn't bother to change the K1 discs, contrary to MB Doc's recommendation. You live and you learn. Fortunately I can pull the K1 out without removing any aft components and could actually leave the valve body in tact. could always swap out for a rebuilt valve body too, but geez this transmission only has 138K miles on it.

My brother who was driving it before I pulled the unit said the 2-3 shift was taking a bit of extra effort. Of course he thought it was normal and didn't mention it until I had the transmission back on.

Anyway, it will shift and it is drivable so I'll have to leave it at that since Mom is expecting me in OH for no later than tomorrow. Of course I won't take the 350.

I'm still interested in any other experts opinion in the meantime.

dpetryk · #6 12-24-2006, 07:47 AM

As I recall there are some large O rings at the bottom of the clutch drums that need to be replaced. Unfortunately, it requires removing some rivets, replacing the O ring then tapping the rivet hole and installing some flat head screws to replace the rivets. This is the only way to replace these O rings. Did you do that? You should have done all the seals and O rings while you were in there

jshadows · #7 12-24-2006, 12:22 PM

Quote:

Originally Posted by dpetryk

As I recall there are some large O rings at the bottom of the clutch drums that need to be replaced. Unfortunately, it requires removing some rivets, replacing the O ring then tapping the rivet hole and installing some flat head screws to replace the rivets. This is the only way to replace these O rings. Did you do that? You should have done all the seals and O rings while you were in there

Yeah, no doubt about it. I was lazy and mainly interested in fixing the reverse problem unaware of the 2-3 problem which is now exacerbated by the change in clearances.

The service manual for the later 722.3xx variants does have a seal replacement after pulling the internal springs on the K1 and K2 packs, but I did not do that. The car is drivable as adjusted at the moment, just not perfect. I'll pull the transmission again when I get a chance.

You live and you learn.