Podguy

What parts did you need and what was the overall parts cost?

Thanks

ammonman

In the transmission I replaced:
(a) B3 piston, all B3 piston seals, all B3 piston return springs and spring retaining plate/circlip (thanks for the tip Greg B.), and B3 piston teflon rings, and mainshaft seal rings
(b) all B3 frictions and steels
(c) all seals and o-rings for the primary pump and front cover
(d) B1 band, all B1 piston seals/o-rings, B1 piston cover o-ring, B1 band reaction unit o-rings and protection switch o-rings
(e) B2 piston lip seal and cover plate o-ring
(f) Filter and pan gasket, control cable o-ring
(g) updated K1 spring (fixes 2-3 shift flare)
(k) Replaced drive plate rivets with bolts

Cost for all that was $560. Had another $600 in the torque tube bearings, $200 in shock rebuild, and about $400 in rear suspension bushings, shock bumpers, rear main seal, etc.

Hope this helps.

Mike

Podguy

It would be nice to have an explanation about how all that fits together in terms of functionality.

It sounds like you will have a long running car.

Thanks

ammonman

I hope the car does run a long time. It has 186k miles on the clock already.

The primary issue I had was very weak action of Reverse. On level ground it would only back the car up when cold. Any kind of incline and there was no movement. The original task was to replace the B3 clutch pack, re-seal the primary pump, and do all the other WYAIT's for the trans (B2 piston update, K1 flare spring, etc.). Once I had it open the damage to the B3 piston due to the over-travel caused by the worn B3 clutches necessitated complete replacement of the B3 piston assembly.

The B3 piston clamps the B3 plate brake to make Reverse gear happen. The B3 plate brake is nothing more than a stack of alternating friction discs and steel discs. The friction discs have teeth around the I.D. that mesh with the planetary gear assembly and the steel discs have teeth around the O.D that mesh with the trans case. When the B3 piston is actuated via hydraulic pressure from the valve body it clamps the B3 frictions and steels together and holds part of the front planetary gear set tight. Do a search on YouTube for video of how planetary gears work. The B1 piston and B1 brake band do the same thing as the B3 piston and plate brake but to a different part of the front planetary gear set and make 1st and 2nd gear.

Mike

Bill Ball

Glad to hear it's all working so well. It's impressive how some of you guys who have never opened a Roger box will tear into it and manage to figure it out, fab tools, etc. I tore into mine only partially and was very intimidated and mostly confused by what I was seeing. If any of my misadventure helped in your case, I'm pleased for that.

ammonman

I'm not quite ready to declare victory yet. If I have a trouble free run from here to Wichita (about 4 hours through Oklahoma) and back I'll plant the flag. I did look at a lot of posts from your adventures Bill along with posts from many others as well as reading everything I could find in the Moorehouse CD's and other online Mercedes 733 trans info. The input from this board is fantastic and the willingness of folks who've BTDT along with our resident subject matter experts (paging Greg Brown, Mr. Merlin, Steve C., Wally, and many others) is part of what makes owning these fantastic specimens of automotive engineering possible for many of us.

I was always mystified by the Rogerbox until I read the material in the Moorehouse collection and put that together with my industrial maintenance experience with planetary gear reducers. Once I put the two together a lightbulb came on in my head. That said, i wouldn't try to do a full rebuild. I don't have the garage space or the uninterrupted free time to stay with the project plus getting all the necessary shims and spacers to set one up would not be cost effective.

Mike

GregBBRD

The nice thing about automatic transmissions is that they either work correctly, right out of the box, or they need to come back apart....there's not much "break-in" required.

There's a couple of strainers down in the "pressure" part of the valve body assembly (the smaller section, towards the rear) that generally "catch" a whole ton of debris when the K3 clutches go bad. It is common for these to be so "flow" restricted that one of the strainers will actually collapse from being plugged up with the debris from the clutches. Really interesting thing to see and think about how much pressure it takes to collapse a pretty darn rigid stainless steel strainer. (It's common enough that I stock new strainers.)

I'd think that you probably removed all of this stuff and cleaned the strainers. Were yours collapsed?

Other than shifting adjustments (and if you re-used the old modulator, you should be really close), not much to be done.

Sounds to me like you are there! Good job!

ammonman

Now you tell me. I did remove the valve body and lower housing that the filter attaches to as i was trying to figure out how to remove the control pressure cable actuator arm pivot pin. I carefully removed any clutch material and sludge that had accumulated but didn't remove or clean any strainers. I tried to keep my dis-assembly of those parts to a minimum so as to avoid dislodging debris and having issues with the valve body. Once I figured out how to get the pivot shaft out I realized I didn't need to touch the valve body or lower cover. Fortunately I can remove and clean the valve body and lower cover leaving the trans in place if it comes to that down the road. I did the final check of fluid level this evening. The level was right where I left it at the MIN mark when hot and in neutral. I added just a smidge to bring the level mid-way between MIN and MAX hot. There was no other signs of any leakage from any part of the transmission.

As far as the modulator goes I had just installed a new one and set the pressure with a gauge when the B3 clutch pack gave out all the way. I think the modulating pressure may be just a bit high as the gear change seems firmer than it was but this could just be a mis-calibrated butt dyno reading. i plan to check the pressure once we get back from OCIC this weekend. I also plan to ask one of the SME's to take my car for a spin this weekend and give me some feedback. Without knowing how a well sorted 928 is supposed to act it is hard to tell what needs attention unless it is completely Tango Uniform or blatantly obvious. I do know that even needing a final alignment, the new rear upper control arm and lower control arm camber bushings have made a world of difference to how the car handles. This alone eliminated a bunch of miscellaneous rattles from the suspension when going over rough patches of road or railroad tracks etc. and have given the car a much more predictable feel to the handling.

Mike

Tony

Just doing some reading..research.

Great thread! well done!

ammonman

Thanks Tony. The trans still performs like a champ. Next time I change fluid and filter I'll go back in and replace those pesky filter screens Greg was talking about.

If you need a tool to take the B1 piston cover off safely, a tool to measure the B1 piston travel, or a tool to take the B3 piston apart from the primary pump shoot me a PM with a ship to address.

Mike

ROG100

Mike,
My gearbox in the GTS started to not engage reverse so it is about to ship the Greg for a rebuild.
150K miles.
Roger

ammonman

Greg is the only person I'd send mine to for a full rebuild. You know it will come back with all the wearable items replaced, properly set up, and all the factory and MB updates plus a few "Doc Brown" tweaks learned from experience.

Mike