Diesel RVs: Re: [diesel_mercedes] 4 bolt tranny throttle linkage and shift issues 722.118

The 4-bolt pan trannys don't have the B2 servo piston problem. They have plenty of their own set of problems....

There should be a pivot point on the top of the cam cover, and the L-shaped arm that pivots there assures that the movement at the transmission is not linear with the movement of the throttle rod. In fact, the transmission shift rod moves very little. This is from the W116 service manual:

http://handbook.w116.org/Engine/617/30-300.pdf

Shifting as you've described is largely caused by mis-adjusted kickdown linkage, and/or defective vacuum modulator, if equipped. It could also be due to dried out and leaky servo seals, especially if there is a delay in shifting into reverse, which is the first to go.

I would certainly look into using the TH400, or, even better, 700R4. Best would be the Aisan from a 4.0 Cherokee or TJ, if you don't mind shifting it yourself (the transmission control module needs inputs from the engine that these old diesels don't provide). The gearing in the Aisin is much better suited to the OM617A torque curves than the GM transmissions. There are several little backyard machine shops selling kits to mate any of these transmissions behind the Mercedes diesels. In the long run, spending $1000 - $1200 on a kit would cost not much more than getting a divorced transfer case set up, and save a LOT of trouble.

Mark (now in Centennial, CO)

From: "Aleph93 aleph93@ca.rr.com [diesel_mercedes]" <diesel_mercedes@yahoogroups.com>
To: "diesel mercedes" <diesel_mercedes@yahoogroups.com>
Sent: Tuesday, July 21, 2015 10:58:29 AM
Subject: Re: [diesel_mercedes] 4 bolt tranny throttle linkage and shift issues 722.118

Bogy,

Question, did you drive the parts car before mounting the engine/tranny in the jeep?
If so, it it act the same at that time?

Has the fluid and filter been changed recently?

Heres' the article regarding the B2 piston:
http://articles.mbz.org/transmission/b2/why/

Broken springs in the tranny, can cause the tranny to shift poorly. Mine had a few broken springs, and had shifting problems at 2-3, so I had the local MB tranny guy put in a shift kit for the tranny. Helped a lot. Also adjusting the vacuum modulator etc.

Rob
'85 300D (722.416 CA '85)
Garden Grove, CA
=

On 7/20/15 10:49 PM, Bogy Wan Kenobi polespearbogy@yahoo.com [diesel_mercedes] wrote:

Guys:

Last sumer I got an 81 CJ7 for a great price. It got better when I sold the bits I didn't want. It came with a th400 and t20 transfer case. I got it because I wanted a jeep and especially wanted to put the engine/tranny from my parts car in one. A couple of months ago I got it legal and have been driving it. It is the 722.118 four bolt with the long arm for throttle position sensing/shift point modification. The tranny came form a different car than the engine did and I do not have any good details about how to connect the "modulator" arm to the throttle so I made a linkage of my own and it moves the rod "linearly" with the throttle.

Question 1: is this right or should the modulator arm only move at the end of the throttle travel.

It has never shifted right - flaring between 2 AND 3, AND THEN SHIFTING ABOUT 25 - 30 mph DEPENDING ON TEMP. (Excuse the caps, I'm not retyping all that.) As of a few weeks ago it would not shift out of second gear when cold unless I got it up to the mandatory shift point as indicated on the speedo. But once it warms up it shifts in an acceptable manner. Once warm it stays in second a bit too long for my taste and still can flare if I don't dance on the throttle just right. But I can live with it.

Question 2: Because the shift starts working right when warm I suspect some gum or varnish in the valve body (or maybe the band servos - who knows) and when it warms up the stuff softens up and allows acceptable shifting again. I was thinking about using a bit of MMO or something to dissolve the sludge (if indeed that is what it is) and wanted you guys' take on all this.

I may just end up putting the TH400/T20 on because I have it and can make an adapter plate to mount it all onto the engine. And then I would have 4 wheel drive without having to figure out how to install a divorced t-case. I'm just looking at options right now. But any thoughts would be outrageously appreciated.

FWIW, I have mounted a 123 instrument cluster on the dash and the odo doesn't work. But using my phones GPS over a full tank of gas I get just under 20 MPG. (3.54 diffs and 33 inch tires add up to 15% faster than the spedo indicates.) Oh yeah The engine is old and tired. A couple of HARD Italian tune ups has helped it to idle smoothly within 30 seconds after start up instead of 30 minutes. And I can't get it to start unless the injection timing is retarded to about 15 degrees BTDC. (spent all day today proving that.) But it's mine, it didn't cost me much and I enjoy the hell out of bonking around town in it. It was a lot of fun to build. And it is still a lot of fun to work on. There's a thousand little things to do.

Still I gotta do something about the tranny shift thing.

TIA.

Bogy.

"Hardware eventually fails.
Software eventually works"
- Michael Hartung