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  #1  
Old 11-09-2012, 05:59 PM
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I thought that transmissions for MB diesels were different than Gas engines?

I thought that transmissions for MB diesels were different than Gas engines? People always said that the gear ratios were different because the diesel had so much more torque.

Then why does the 1997 E30D have the same transmission as a 1997, 1998,1999, C230 gas vehicle? They both have the 722.600 transmission.
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  #2  
Old 11-10-2012, 05:19 AM
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I think the om 617.951 had the same trans as a gas 300.
I the trans engines horsepower is close they can share
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  #3  
Old 11-10-2012, 06:21 AM
t walgamuth's Avatar
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I cannot speak about newer trannies but in a 123 the transmission itself is the same but the mechanism which controls the shift points is different and causes the tranny to shift at a lower rpm in a diesel application because of the much lower rev limits.
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  #4  
Old 11-10-2012, 08:48 AM
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I am using a 190e 2.3 gas transmission with my om601 conversion and it drives/shifts just fine, I never let it get much over 4000-4500rpm anyways, so in practice it makes no difference.

However my car is a bit slower off the line as I have the original 3.07 diff instead of the 3.45 or 3.65 or whatever a normal 190d 2.2 would have. Makes for nice cruising at 55-75 though.
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  #5  
Old 11-10-2012, 08:58 AM
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Having a vacuum input to a diesel tranny tells us Benz borrowed a gasser design for our cars. The "throttle" modulated vac input is what allows interchangability.
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  #6  
Old 11-10-2012, 09:01 AM
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I have a copy of the 722.3/4 Operations Manual. It makes no distinction between engine type.

Quote:
Originally Posted by t walgamuth View Post
I cannot speak about newer trannies but in a 123 the transmission itself is the same but the mechanism which controls the shift points is different and causes the tranny to shift at a lower rpm in a diesel application because of the much lower rev limits.
Have a reference for that theory?
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  #7  
Old 11-10-2012, 09:33 AM
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I too am wondering about this... I replaced my 2.8L M104 with a 2.9L 602 Turbo but am still using the original tranny and diff that came with the gasser. It's not yet finished but will be soon... so I don't know if I'll have issues with the gearing. Predictions anyone?
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  #8  
Old 11-10-2012, 10:01 AM
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Quote:
Originally Posted by qwerty View Post
I have a copy of the 722.3/4 Operations Manual. It makes no distinction between engine type.



Have a reference for that theory?
It is a shame that there is so little information written in English for Mercedes automatic transmissions. Chapter 27 is missing from the English version of the FSM.

Chapter 27 does, however, exist on the German language FSM CD - these can occasionally be bought on ebay(.de).

Chapter 27 is also available (in English) on WIS - but I don't think any private person could afford to have that.

In chapter 27-001 there is a whole list of hydraulic pressures and the conditions / speeds at which they should occur.

Essentially each transmission type is very similar be it for a diesel or a petrol engine - however, differences such as differential final drive ratios and the maximum engine speeds mix things up a bit.

It seems to me that the "diesel transmissions" have different valve bodies. The valve body in the 722.303 that I took to bits recently has additional valves and bits missing compared with the general information presented in the (German) FSM in chapter 27. I've highlighted some of the differences in this thread =>

722.303 in bits photo shoot

This is also the case for the 722.1 transmissions - some references are made to the differences here =>

722.118 Automatic transmission rebuild (Monster DIY)

At the moment I'm trying to get to the bottom of all of the differences - but it is a bit of an up hill struggle. For example - I'm not 100% sure if the governors are specific to transmission type or if they are common for all types. I get the feeling with the 722.1 governor that it is tuned to type - but I think for the 722.3 it is a generic thing that is adapted for "diesel use" at the valve body...

...if I ever get to the bottom of it all I'll start a thread - I'm already some of the way through a write up "in my own words" of the chapter 27 information that I have - but life is getting in the way at bit here at the moment.

The only reference to different gear ratios that I can find is for the 722.3 transmissions - specifically the 722.323 and 722.350 transmissions which are pre-August 1988 transmissions fitted to big V8s (petrol of course)
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  #9  
Old 11-10-2012, 11:12 AM
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On background, I'm running an OM617 with a 722.4x in my 107 chassis. It's been a really fine swap, but recently the transmission has developed shifting problems and will need to be swapped out. I've picked up a spare 617 and the matching 722.3x transmission and am gearing up to pull the engine/trans and swap in the 722.3. However I've also got a 722.3 from the original V8.

In light of the info on this thread I wonder if it would be helpful to swap in the gasser tranny and just see what the results are like? I don't have the exact model numbers at my fingertips but could get them later today.

Would it be worth the chance? Any thoughts or interest in this potential data point?
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  #10  
Old 11-10-2012, 12:10 PM
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Quote:
Originally Posted by mach4 View Post
...
In light of the info on this thread I wonder if it would be helpful to swap in the gasser tranny and just see what the results are like? I don't have the exact model numbers at my fingertips but could get them later today.

Would it be worth the chance? Any thoughts or interest in this potential data point?
I for one would love to have some real world data and impressions on this sort of thing.

Given the final drive gearing and wheel size etc we can quite easily work out at what speed a particular pressure should occur. It would be interesting to find out if it can be reproduced under different circumstances - in other words can the modulating pressure that is influenced by vacuum be tuned to get the engine and transmission to behave as though there is a different engine and transmission configuration?
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1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #11  
Old 11-10-2012, 12:41 PM
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I just checked the transmission numbers
300D - 722.315
380SL - 722.312

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  #12  
Old 11-10-2012, 01:30 PM
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Quote:
Originally Posted by mach4 View Post
I just checked the transmission numbers
300D - 722.315
380SL - 722.312

Here's what I know - found from EverythingBenz - Mercedes-Benz Forum and Web Search Using Google

The 380SL had the 722.312 but it also shared the 722.304 with the 380SLC - both cars and combinations seem to have had a 1:2.47 diff

The 300D (turbo diesel 123.133) had either the 722.315 or the 722.416 with either a 1:3.07 or a 1:2.88 diff (probably only in 1985)

The 300SD (126.120) had the 722.303 or the 722.416 again with either a 1:3.07 or a 1:2.88 diff

I guess I should post up the shift data next then...
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1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #13  
Old 11-10-2012, 02:28 PM
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It would be interesting to do a side-by-side comparison of the gas and diesel governors of similar 722.3 transmissions. I imagine that a close look at the flyweights would show some differences. In the VW world, these flyweights are modified in order to change the shift characteristics when converting to a higher revving engine.
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  #14  
Old 11-10-2012, 07:54 PM
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I used the diesel torque converter on my setup because the gas one is larger and would not fit inside the huge flywheel on an om601....
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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 76k - mine - (OC-80,500)
'17 Metris(VITO!) - 7k - wifes (OC-10k)
'01 E320 Wagon - 159k - mine (OC-160,000)
'89 420SEL 166k - mine (OC-167,000)
'01 E320 - 168k - dad's (OC-171,500)
'07 E350 Wagon - 131k - dad's (OC-132,500)
'01 SL500 - 49k - dad's (OC-52,000)
'09 E350 4matic Sedan - 128k - Brothers (OC-128,000)
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  #15  
Old 11-10-2012, 08:53 PM
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Quote:
Originally Posted by pawoSD View Post
I used the diesel torque converter on my setup because the gas one is larger and would not fit inside the huge flywheel on an om601....
Would not fit how? My engine 602 and tranny(from an m104) have been mated up already, not yet run. I'll try and rotate the engine by hand in a while, you got me concerned.
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86 230E (-->300D)
87 300D (-->300TD)
68 250S w/ a 615 and manual tranny (RIP)
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95 S280 "The KRAKEN" (Turbo 2.9 602 transplant)
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