6.9 Transmission Upgrade

[Oversize]

Ok here's some info that I've copied from another site where I discussed a transmission upgrade:

Mark, 560SEL got the 722.323 and the 420 got a 722.324. It appears the 722.3 transmissions used behind the V8 cars were W4A-040 units, with 040 being the torque rating in mkg. The V12 cars had a 722.362 unit which was a W4A-055. 40mkg is about 392NM or 289lb/ft. 55mkg would be about 539NM or 398lb/ft of torque. Considering that the 6.9 transmission was rated at 050, I think the V12 unit would work, although you could probably get by with a 560SEL unit as the euro version of that engine was pretty damn close to what a 6.9 made. I may be incorrect on the mkg vs nm. The early transmissions in the late 60's were rated in Mkp or mkg, the later ones may in fact be rated in NM, so the ratings would actually be a bit higher....400 and 550NM.


Chris in Phoenix

That doesn't sound right because if a Euro 6.9 can produce 550Nm, it'd blow up both it's own trans, plus that of the V12. From what I've heard the Aussie 600SEL produced 300Kw and 580Nm and would also grenade it's own trans going by those figures

Mark

Well, the 6.9 transmission was a W3B-050 and the 050 is the torque rating of the transmission, either in mkg or nm. They never made a 3 speed with a higher torque rating. The 6.3 was a K4B-050, same torque rating, but a 4 speed with fluid coupling. Also remember in engineering there is usually a "cushion" built into the specs....I would imagine the rating of 500NM is a bit on the conservative side, with the actual capacity being a bit higher.

No electronics, 722.3 transmissions were all mechanical. No lockup converter either. Also, the 722.3 was used in Porsche 928.

Chris

 

[Oversize]

Could we have accidently discovered why the stator splines fail?? Or did they grossly understate the input limits?

BTW I found another site that said the 600SEL used the 722.621 trans but it's likely there's a lot of inaccurate info out there. A different site gave these ratio figures for the 600SEL:

1th gear ratio: 3,87:1

2th gear ratio: 2,25:1

3th gear ratio: 1,44:1

4th gear ratio: 1,00:1

Reverse gear ratio: 5,59:1

Gear Ratio (end): 2,65:1

RPM at 120 km/h (theoretical): 2.450 rpm

 

[Oversize]

From the same site regarding a 1986 560SEL:

1th gear ratio: 3,87:1

2th gear ratio: 2,25:1

3th gear ratio: 1,44:1

4th gear ratio: 1,00:1

Reverse gear ratio: 5,59:1

Gear Ratio (end): 2,65:1

RPM at 120 km/h (theoretical): 2.550 rpm

 

[Oversize]

Ratio's 6.3 versus 6.9:

6.3
I 1 : 3.98
II 1 : 2.46
III: 1 : 1.58
IV: 1 : 1.00

6.9
I 1 : 2.31
II 1 : 1.46
III 1 : 1.00

 

[Oversize]

Well the goal isn't complex, but the solution certainly is! I want better acceleration than the 6.3 (and many other cars on the road)! Changing the final drive (diff) alone would go a long way towards that goal, but it would also reduce the top speed. I then got thinking about the transmission.... Seems most 4 speeders have a better 1st gear ratio than the 6.9, which would get one into it's ideal rev range even quicker, instead of bogging down off the line. Tyre hook-up is an issue, but I'm not considering swapping the hydro for springs, or anything that radical. Wider, sticky tyres will help.

An overdrive trans would be ideal but I'm not even sure if the 600SEL trans has that function. Then there's the availability issue and I've heard the trans is far from perfect, but it's the only one (on paper) that appears to be able to tolerate the high torque of the M100 and not need an ECU to operate.

The figures I've posted thus far may not be accurate as I have my doubts on their source. I should know more tomorrow when I ST someone with some MB tech data books....

I'm not interested in a manual box, or a swap to a GM trans with the info I have so far.

 

[motec 6.9]

W140 Series 1 600 4 speed trans. Series 2 W140 600 5 speed trans carried onto W220 series . There are only 2 5 speed boxes difference in number of clutch packs in drums between V8 and V12 trans. So it doesn't matter if rebuilding trans top spec in S65 rated at 1000Nm torque limit. Same box in 300C called NAG1 http://en.wikipedia.org/wiki/Mercedes-Benz_5G-Tronic_transmission

 

[Oversize]

With a lower 1st gear and final drive, plus a lighter weight, it's obvious why the 6.3 is quicker.

Mark

Be careful with changing rear axle ratios. I had a customer here with a Euro 6.9 that was bored out to a 7.3, custom pistons, etc... Anyway, it also had a 3.07:1 rear axle ratio in it and the thing was not fun to drive at highway speed. I ended up putting a stock rear diff back in it and it made all the difference in the world. With the lower ratio, acceleration was not noticeably faster off the line, and the engine was revving so fast at 60+ mph that it ruined the whole 6.9 experience, not to mention the engine was not in it's "sweet spot". These engines have so much torque that the tall rear axle ratio does not matter, and one of the joys of driving a well sorted out 6.9 is that they have such "long legs" on the highway.

Chris

 

[Oversize]

Regarding the 6.3 diff:

2.82:1 or 2.85:1, depending on the exact generation.

 

[motec 6.9]

Hi Mark did you see reply about 5 speed box.

 

[Oversize]

Description of Operation, Auto Trans 722.3 (W4A040) dated 11/85. I wonder if the trans type is stamped, or cast anywhere on the housing? The 40 does indicate Max input torque in Nm, as mentioned earlier in this thread by ctmaher.

The ratios are:
1st 3.68
2nd 2.41
3rd 1.44
4th 1
Reverse 5.14

I had to inspect the car to get the final drive (differential) ratio which is 2.47. This ratio is stamped on the RHR of the diff housing machined face, just below the tag that indicates LSD and the rear cover plate with cooling fins. It also has the number 636313 stamped in the same place and I'm not sure what that means.

So if you could somehow fabricate an adapter to connect this trans and you didn't blow it to pieces with the torque of the 6.9, I wonder what max speed you could achieve on the salt flats??

And if you didn't grenade it on a launch, I wonder how the acceleration would compare to that of a standard 6.9....

Mark

 

[motec 6.9]

Sorry Mark but under no circumstance do I have any interest in the old 4 speed trans . It is the 5 speed or nothing with Mb trans or fitting Gear vendors to current box. 4 speed has no overdrive top gear so I have no interest in knowing about them they are a dead end with no positive points.

 

[motec 6.9]

This gear box or I will not bother. http://en.wikipedia.org/wiki/Mercedes-Benz_5G-Tronic_transmission

 

[Oversize]

Here's a transmission comparison chart I prepared earlier in Excel but I can't work out how to post the file so here's just a copy/paste:

1 2 3 4 5 6 7 R Torque Rating Diff Ratio

6.3 3.98 2.46 1.58 1.00 na na na 500Nm 2.85
6.9 2.31 1.46 1.00 na na na na 500Nm 2.65
560SEL 3.68 2.41 1.44 1.00 na na na 5.14 400Nm 2.47
600SEL 3.87 2.25 1.44 1.00 na na na 5.59 550Nm 2.65
Torqueflite A618/47RH 2.45 1.45 1.00 0.69 na na na 2.21 610Nm
Torqueflite 48RE 2.45 1.45 1.00 0.69 na na na 2.21 610+Nm
Turbo Hydra-Matic 3L80HD 2.48 1.48 1.00 na na na na 2.07
Turbo Hydra-Matic 4L85E 3.059 1.625 1.000 0.696 na na na 2.294
Powerglide 1.76 1.00 na na na na na
FMX 2.40 1.47 1.00 na na na na 2.00
Veyron 3.18 2.26 1.68 1.29 1.06 0.88 0.80 3.64
VE SSV (6L80E) 4.03 2.36 1.53 1.15 0.85 0.67 na 720Nm 2.92

 

[motec 6.9]

Not trying to be mean Mark but it must be overdrive to bother with the effort required. And as I said control is no longer a problem due to Chrysler use after market came on board.

 

[Oversize]

I just had to post all that to include all the detail I could. There's no way I'd go back to a 6.3 box for a 6.9...

The only problem with GV is weight and fitting it into the tunnel. That's why a all-in-one box is a better option if one can be found that will work without major headaches and cost

 

[motec 6.9]

This is the only Mb box of any interest
5G-Tronic (W5A580/Large NAG)[3]1st 3.588 2nd 2.186 3rd 1.405 4th 1.000 5th 0.831 -3.167 -1.93
However, all V12-powered cars such as the S600 and S65 AMG still retain the 5G-Tronic, which has a torque capacity of 796 lb-ft

 

[motec 6.9]

I have done quick measurements to 5 speed it will fit as external width and height similar to 3 speed just length requiring new tail shaft. Torque Fabrication have agreed to fit just need to find funds.

 

[Oversize]

Going by the ratios a 6.3 would rev even higher than a 6.9 at 100kmh. What's your 6.9 doing (RPM) at 100kmh Motec?

 

[motec 6.9]

Just over 2400RPM. And yes that's why 6.3 has lower top speed of 137MPH.

 

[Oversize]

Personally I like the idea of this one:

Torqueflite 48RE 2.45 1.45 1.00 0.69 na na na 2.21 610+Nm

Just add a GV for an 8 speed trans!!