6.9 Transmission Upgrade

[Oversize]

The Aussie 560 uses a 2.47 final drive which is another reason why it's slower 0-100 than a Euro one.

 

[Styria]

SEL 69L (David Rollason) had a 450 differential fitted to his 6.9 that he sold some while back. He did this on the advice of a friend of his, and obviously I did have opportunities to drive his car. To be perfectly frank, I really couldn't tell all that much difference despite that fact that David DID think it made his a more satisfying, and faster car, to drive. Personally, I still think that Gleaming Beauty had the legs on his car.

It is feasible that a 6.3 box could be used behind the 6.9 engine, but even though it is a four speeder, if one would utilize first gear, you would just about rip out the diff/rear axle arrangement - a very, very costly option on 6.3s and accompanied by heaps of work. This weakness in the 6.3 drivetrain is probably one of the reasons why the 6.3 needs special, loving and tender care. Plus, the box has two looped bands one of which is prone to let go, and another expensive repair option is on its way. I don't know - I think I'll stick to what I've got for the time being. Regards Styria

 

[c107]

SEL 69L (David Rollason) had a 450 differential fitted to his 6.9 that he sold some while back. He did this on the advice of a friend of his, and obviously I did have opportunities to drive his car. To be perfectly frank, I really couldn't tell all that much difference despite that fact that David DID think it made his a more satisfying, and faster car, to drive. Personally, I still think that Gleaming Beauty had the legs on his car.

Was his car an aussie delivery? if I recall right, your GB is a high comp motor, so I could easily see a high comp motor being about the same as an aussie car with a 450 rear end???

 

[Styria]

Hi Bryce, yes it is. I have always found ever so much, or perhaps so little, of a difference between the high and low compression engines. Seat of the pants and ears demonstrate an aural difference, as well as an ability for the high compression engine to "want to go on with it". Maybe I am barking up the wrong tree, but there just seems to be that little bit of a difference. Regards Styria

 

[Oversize]

My people are telling me the Benz 5sp is far too hard with programming the controller the main hurdle. Currently looking at a GM 6L90E 6sp trans which is normally mated to the HSV LSA engine so it should be able to take the torque of the M100.

 

[Oversize]

 

[Oversize]

FYI here’s the Benz box and ratios that were considered:

 

[c107]

Have you seen these transmission controllers?

Apparently folks are using them to adapt modern Mercedes transmissions ns to the m117.

http://mbturbo.com/new-722-6-gearbox-in-you-old-car/

http://soundgermanautomotive.com/pcs/

Not specific to the m100 but could be of interest.

 

[Oversize]

Seems more questions than answers & PCS was mention by the people I’ve consulted. Apparently they supply OEM with little after sales support. Calibration, mapping & tuning are the big issues here. Unless you’re an expert or have very deep pockets it’s not the way forward.

It does make some sense if the bolt patterns are the same but the M100 is a different animal.

Things have progressed so far with modern transmissions integrating with engine ECUs to do things like reduce power on gear changes to protect various components. The NAG1 is not plug n play and may never be so cause it’s an older trans with little R&D interest. The 6L80E & 90E mapping is nearly done so full control is more likely.

Another hurdle may be the speedo drive & im hoping a later unit can be adapted.

 

[motec 6.9]

NAG1 was Chrysler version of Mercedes transmission and companies is US are making 100hp plus versions and you can buy independent controller's . As for Euro versus Australian version stock euro is 230hp at wheels Australian is just on or under 200hp

 

[motec 6.9]

Here is another stand alone control box that can control the NAG1 or 722.6 transmission https://automatictransmission.com.a...ysler-nag1-automatic-transmission-controller/

 

[Styria]

I guess it is fair to say that there have been no significant developments on these discussions. That is quite understandable when one considers the cost involved, and the skilled technicians/engineers that would need to be found to implement some of those changes and modifications. My observations are not meant to be critical or dismissive of some of the changes proposed or talked about, but I am mindful that at this stage of my life and 6.9 ownership I tend to walk in the opposite direction. Why ?

One would have to question the benefits of improved acceleration from rest and the ability to maintain a more relaxed cruising speed on the open road. Cars have moved on considerably since the 6.9 would have been considered "King of the Seventies" and, in my opinion, the fitting of a 450 differential is a retrograde modification. I have just driven, and I am working on a 6.9 with that exact same differential ratio, and in my opinion the car is now noisy (mechanically) in operation and certainly seemed to be short legged on the M2 when I drove it back to Seven Hills, where I now keep my cars. I guess the 6.9 wasn't helped by the fact that I had just delivered a 2016 VW Golf Blue Motion with the 4 cylinder turbocharged engine. On the M4 into the City (well, not quite that far), I was staggered by the willingness of that car to continue on well past the 90 km/hour speed limit, and it was doing that in absolute quietness. Sorry to say, but one or two bars above that particular 6.9.

As I see it, the total attraction of the 6.9 is the torque - from 1500rpm in second gear, and the scenery becomes a blur. Take it up to 2.5 to 3.0, and that is where these cars shine. To own a 6.9 (unchanged) is one side of the equation, the more modern cars occupy the other side. Personally, I would leave the 6.9 as it is standard apart from, perhaps the fitting of a 2.47 differential providing acceleration from rest almost equal to standard, with a more relaxed and economical cruising speed. Regards Styria

 

[c107]

I guess it is fair to say that there have been no significant developments on these discussions. That is quite understandable when one considers the cost involved, and the skilled technicians/engineers that would need to be found to implement some of those changes and modifications. My observations are not meant to be critical or dismissive of some of the changes proposed or talked about, but I am mindful that at this stage of my life and 6.9 ownership I tend to walk in the opposite direction. Why ?

One would have to question the benefits of improved acceleration from rest and the ability to maintain a more relaxed cruising speed on the open road. Cars have moved on considerably since the 6.9 would have been considered "King of the Seventies" and, in my opinion, the fitting of a 450 differential is a retrograde modification. I have just driven, and I am working on a 6.9 with that exact same differential ratio, and in my opinion the car is now noisy (mechanically) in operation and certainly seemed to be short legged on the M2 when I drove it back to Seven Hills, where I now keep my cars. I guess the 6.9 wasn't helped by the fact that I had just delivered a 2016 VW Golf Blue Motion with the 4 cylinder turbocharged engine. On the M4 into the City (well, not quite that far), I was staggered by the willingness of that car to continue on well past the 90 km/hour speed limit, and it was doing that in absolute quietness. Sorry to say, but one or two bars above that particular 6.9.

As I see it, the total attraction of the 6.9 is the torque - from 1500rpm in second gear, and the scenery becomes a blur. Take it up to 2.5 to 3.0, and that is where these cars shine. To own a 6.9 (unchanged) is one side of the equation, the more modern cars occupy the other side. Personally, I would leave the 6.9 as it is standard apart from, perhaps the fitting of a 2.47 differential providing acceleration from rest almost equal to standard, with a more relaxed and economical cruising speed. Regards Styria

I think the other change is that 6.9s are now worth more than they used to be, and unmodified cars are worth a lot more than modified. So you could end up spending $10k for this change and then loose $5k of the value of your car.

A 2.47 diff would be hard to find in LSD, as you would need to find an import 380SEC.

 

[Styria]

I agree with you on your observation in the second paragraph. I have a 2.47(rebuilt) differential on hand which, of course, does not have the LSD feature. Two ways to tackle this:

Firstly, just fit it in its present configuration and be "extra careful" on a wet road - and I could do this....., or

Secondly, hand both my original and the replacement diff. to Specialists and let them combine the best features from both units.

Regarding your point of originality, I guess it would be an issue for some prospective buyers. On that score however, I would be confident in asserting that my Gleaming Beauty would appeal to even the most discerning buyer if it wasn't original having regards to its overall, well maintained condition. Regards Styria

 

[Oversize]

This is certainly a significant modification & not something you can achieve overnight. And probably not something you’d want to do if you’re worried about resale....

However it would be interesting to see how the M100 would perform coupled to a modern trans. It is bordering on a complete driveline swap, which would likely completely change the character of the car, to something far more modern. Which kind of defeats the purpose of having an old classic. You have to ask yourself why not just buy a new(er) AMG?

This is a lower priority for me now, put behind my manifold project. However it’s still something I will pursue in the future on a car that was destined for the wreckers.

 

[c107]

Firstly, just fit it in its present configuration and be "extra careful" on a wet road - and I could do this....., or

Personally I wouldn't want to lose the LSD with all that torque. Even a 450 can be a be a bit of a handful with an open diff.

 

[sean sherry]

Interesting observation on how to decrease the value of a Car by modifying it.
Even restoring one can be a money pit...... friend who rebuilds/restores wooden Bodies of Post War Riley's, is realistic when asked, what is the Riley was worth after spending $100,000 on a total restoration, ....... about $25,000