Why a 3 speed automatic?

[bbnlv]

Does anybody know why Mercedes went from a 4 speed automatic in the 60's and early 70's to a 3 speed and then back to a 4 speed again.  I hate the fact my 6.9 only has a 3 speed automatic!

[Big_Richard]

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[bbnlv]

I would love the lower first gear!  I remember the first time I drove a 300sel 6.3.  I lit the tires up across an intersection!  I loved that car!!!  I had a 94 E500 and I hated that is took off in second unless I slammed the pedal to the floor.  The car felt lazy for having over 300hp.  WFT I thought Id ask!   

[jbrasile]

There used to be a mod kit you could install to make all 4 speed trannys start in 1st gear. You need to replace the valve body if I am not mistaken.

The 4 speed boxes in earlier cars used a viscous coupling instead of a torque converter, that made them a lot more direct but also jerky and sometimes downright rough. MB's 3 speed transmissions used in V8 cars were one of the best at the time, providing smooth and  well timed shifts that make almost perfect use of the engine's torque band. With the introduction of the 5.0 M117 engines came the modern 4 speed box with torque converter, that really transformed V8 powered models, making them super responsive and fast. The best car to do a comparison is the 450SLC 5.0 and  500SLC, the 5.0 used basically the same transmission as the regular 450SLC while the 500 had the newer 4 gear trans, engines are basically identical but while the 5.0 will do 0 to 60 in almost 9 seconds, the 500 does the same thing in 7.8 and what a difference in feel...

Tks,

Joe

[Big_Richard]

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[s class]

......I remember the first time I drove a 300sel 6.3.  I lit the tires up across an intersection!.....

A properly sorted 6.9 will do that too.  I live at 1800m altitude, and my blue 6.9 euro will spin both rear tyres basically half a block long, and in fact they only really stop spinning if I lift off the gas.  So no, I really don't want a lower gear in my 6.9.  Its a handfull enough already. 

[nathan]

merc 4 speeds are not about a burst for acceleration with 1st.  they are for towing or steep descents.  if you put these 4 speeds into first, you get about 30kmh out of them before they are screaming and you get a jerky change to second. so a complete waste of time for drag racing.
you can mod the 4 speeds or later 126s (and 124s?) had the shifter enable you to change it into 1st manually where you could hold it. alternatively if you had the earlier model, you just put it into 2nd at the lights then back into D, and it would start in first.

[Big_Richard]

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[s class]

I don't think XWX's would allow that.  I've got firestones on that car at the moment, but it could also do it with the previous Goodyear Eagles. 

[TJ 450]

That just about covers it. Even an overdrive unit/gear would be of questionable use, requiring kickdowns for brisk passing/acceleration at speed, thus making such maneuvers less instantaneous, and not so effortless.

When all is done and done, MB knew exactly what they were doing.

Tim

[motec6.9]

Hi if you want to fit a 4 speed auto to your 6.9 it will set you back at least $7000 about $3500 for the kit no gearbox plus fitting and Franz is the only person who has made the kit .Unless you can convince some engineering shop to do it for . There reply will always be just buy from the person who has the kit if it is available  http://forum.w116.org/test-drive/motec6-9-work-so-far/msg90665/#msg90665  . 

[jbrasile]

I don't have the figures in front of me, but I think the ratios on the 4 speed boxes are lower than on the 3 speed and that is why on the SLC you can feel a tremendous difference while driving.

MT I think you are right bout the 6.9 box on the 5.0, in fact I understand that transmission is actually a beefed up version of the regular 450 box, and yes, Porsche's 928 did use MB's 3 and 4 speed installed in the rear with a torque tube.

Nathan, in my 500SLC if you moved the shift lever into 2 and left it there the car would start in 1st and shift only up to 3rd, that was the only MB I have ever seen behave that way.

Tks,

Joe

[adamb]

I don't have the figures in front of me, but I think the ratios on the 4 speed boxes are lower than on the 3 speed and that is why on the SLC you can feel a tremendous difference while driving.

MT I think you are right bout the 6.9 box on the 5.0, in fact I understand that transmission is actually a beefed up version of the regular 450 box, and yes, Porsche's 928 did use MB's 3 and 4 speed installed in the rear with a torque tube.

Nathan, in my 500SLC if you moved the shift lever into 2 and left it there the car would start in 1st and shift only up to 3rd, that was the only MB I have ever seen behave that way.

Tks,

Joe

I used to own a 1981 W126 380SE which always started in first even though it was a 4 speed auto. That was standard. As far as I recall the 3818cc motors used gearboxes which started in first and the later 3838cc motors which came around 1982 used gearboxes which started in second.

[mirafioriman]

My 2 500 SELs and my current 420 SEL all start off in 2nd as standard. If you drive it as a manual and start in first it feels appreciably quicker. Thinking about it though if you floor it from a standstill in drive they start in first anyway. At normal throttle openings they start in second.

[Tony66_au]

Hey BB I see you are a Jag guy as well!

So here the thing, I've messed with a few V12 Jags and they always felt slow off the mark, Why?

Because they have taller diff ratio's, it is also partly why they are so thirsty.

I had the chance to play with a Daimler Double 6 (Same 5.3lt inj Jag V12) that had a diff from an XJ6 and the thing was a launch monster!

Why?

Lower diff ratio.

And its the same with many luxo barges, they are geared high for smooth clean take off and good highway speed.

As for Benz's?

I have owned and driven 2 with a 4 speed, a 300SEL and a 230TE and first gear was more a crawler gear than anything and you really had to punch it hard at take off to get it to engage and with the US spec engine id say they are a bit slower than usual.

So a Merc 4 speed may be the answer but you will need it shift kitted to use 1st and it will change the characteristics of the drive, id suspect BIG time.

Tony