W126 4-speed auto to W116?

[Andrew280SEL]

Don't know exactly how much this qualifies as as performance upgrade or modification, but if it can be done it certainly ain't a factory job so I guess it will be a modification


Anyway, I'm just wondering if you knowledgeable guys can help me here at all.

My question is, is it at all possible to mate a W126 4-speed automatic transmission to, say, a W116 350SE?

And if so, would it be worth it vs. the inevitable cost?

I guess the reasons are obvious. Having been in a W126 380SE (which has the same M116 motor as you all would probably know, but has a displacement increase) I realised, except for the W126 being lighter of course and the 3.8ltr having a bit more torque, that the low down acceleration and step off was considerably better with that lower first gear being utilized. Also, I assume all the V8 W126's have the same transmission, but I could be wrong.

It wouldn't be something I'd be doing right away obviously, I've got too much to else to spend money and time on, but something to think about later down the track and I'd just be interested to know.

Cheers

 

[116Benz]

Depends if they changed any of the bolt patterns during change from iron to alloy, worst case sceanrio you'd have to get an adapter plate made up to fit everything. if your getting a 126 box, might pay to check the diff's as well.

 

[Andrew280SEL]

It also occured to me that due to the most likely size difference between models, I would have to look at a different tail shaft size...perhaps. I'll have to check that too.

 

[Michel]

It would be great if one could have an extra gear ..... especially in when you need that extra ooomph off the mark

But then again... I use th 690SEL for that

 

[Andrew280SEL]

It would be great if one could have an extra gear ..... especially in when you need that extra ooomph off the mark

But then again... I use th 690SEL for that

Yes, well I reckon if the 690SEL had an extra low first gear your neck wouldn't be intact Michel

But I reckon the 350 could really benefit from one. My 280SEL is actually quicker off the mark because of it's 4-speed.

 

[WGB]

Most Mercedes 4 speed autos up to about 1992 always started in second unless provoked by rapid full throttle or manual selection of Low.

My 1994 124 E280 was my first new Benz that started in first each and every time (The 124 E320 of the same year didn't). After my previous 1987 126 300SE which routinely started in second I initially really enjoyed the extra oomph at the lights until winter came and the car would spin it's wheels all over the place as there was no traction control. My next car had a five speed auto that started in first but had traction control.

I believe there is a kit to make a 126 box always start in first which would make it worthwhile.

Bill

 

[Andrew280SEL]

Yeah, I'd even be happy to just have it stock where it's 'hidden'. I don't mind shifting the transmission into L when I want it to- heck I'm used to doing it in the 280SEL, it's like driving it like a manual...but not.

Anyhow, it would appear the bolt patterns are indeed different going on this quote from OzBenz.net:
http://ozbenz.net/viewtopic.php?f=10&t=2847&view=previous

The 4 speed auto (722.3) will only bolt up to the alloy block versions of the M116 and M117 engines (3.8. 4.2, 5.0 & 5.6). The transmission bolt pattern differed from the earlier 3 speed auto (722.0) which was used with the iron block M116 and M117 engines (3.5 & 4.5).

However, like 116Benz suggested, so long as it can be done for a sane price an adapter plate might be the go.

I'm seriously considering it now, I really think it would be a good match for the 350.
Of course, I still haven't checked out availability or general prices for used W126 transmissions...but they couldn't be too hard to get hold of...surely

 

[Styria]

Hi Andrew, I have been thinking what's been written in this thread. Obviously, until one had the two boxes side by side, mating the 126 box to the 350 would be guessing at best. However, there are four speed boxes in the 116 range, and I cannot see any reason why that type of box would not fit. True, it normally starts off in second, but first gear is readily available by throttle opening or selecting it manually. If you want me to do more homework on this subject matter, please let me know. Regards, Styria BTW, a four speed box from a 108/109 should fit comfortably. I have all the hardware and box for that.

 

[Andrew280SEL]

Really?

Thanks Styria, well, that could certainly work...

The 108/109 idea sounds good too. The only thing is, that transmission wouldn't have the torque converter, would it? Having never driven any Benz older than the W116, I have no idea what they feel like in comparison, but I was led to believe the pre-torque converter boxes were no where near as smooth. Or is the difference not that great?

Thanks

 

[Styria]

Hi Andrew, you know, I've got to put my thinking cap on and also do some checking on your behalf. Right now, if memory serves me right, it was only the 6.3 and the M189 engined 300's that had a fluid coupling. 280's and 3.5's had a torque converter - but I need to do some homework and could stand to be corrected. It may take a couple of days. Regards, Styria

 

[Andrew280SEL]

Hey Styria,

Thanks for that, much appreciated. I'm not worried how long it takes, unless it was a straight swap it's not something I'll be doing right away anyway

 

[WGB]

I thought all the earlier cars had a fluid flywheel and no torque converter - 280's 350's and US 280SEL-450's

Bill

 

[Andrew280SEL]

Hi Bill, so did I but I wasn't 100% sure.

I just looked at Wikipedia though, and it would seem your right:

When the V8 engined cars were introduced in 1970, the default transmission choice was the four speed automatic box, connected via a hydraulic clutch with no torque convertor. Buyers could still opt for a four speed manual box, however, and benefitted from a price reduction if they did so. The 4.5 litre version offered from 1971 but only in the USA, was fitted with a three speed automatic box with a torque convertor. This engine/transmission combination would become more generally available when incorporated in the successor model.

http://en.wikipedia.org/wiki/Mercedes-Benz_W108

 

[Andrew280SEL]

Okay, so I've been having a bit of a think about it.

It would appear the torque converter transmission was only really available (at first) in the form of the three speed auto, and then of course then the 4 speeds fitted to the W116 280's.

So realistically, any of the earlier V8 4 speeds would have fluid couplings.

So here's the thing I'm still going over in my head: I've read, that when the three speed with torque converter was introduced, "initial step-off was improved" and "shifting was smoother" etc etc.

But I remember on W116.org, 'Bahnstormer109' was saying how his 109 (with the same 3.5 motor) had the three speed auto equipped to it after the original 4 speed went to gearbox heaven (or at least needed a rebuild...).
He said he hated having the 3 speed in that car compared to the 4 speed...reckoned it was less responsive and more sluggish.

So I'm a little confused and not sure what to think. Is it just that the 3 speed gives better movement off the line and smoother shifts, but the 4 speed would give realistically better acceleration?

Not that it's a big deal. I mean, it couldn't be too hard to get a W116 280SE 4-speed auto transmission and I imagine there is a way to connect one up. I don't think the M116 motor would be too much for it either, so long as I don't go insane with 1st gear launches

What does anyone think?

 

[Mercules]

If you are going to go to the trouble of fitting a 4 speed gearbox, why not just get say.... a 4.0 litre Ford engine with a 4 speed electronic gearbox... I hear they are readily available and easy to install

 

[Andrew280SEL]

If you are going to go to the trouble of fitting a 4 speed gearbox, why not just get say.... a 4.0 litre Ford engine with a 4 speed electronic gearbox... I hear they are readily available and easy to install

Well Cam, I do have a bit of a purist side to me.


Sure I'm modding the 350SE to a degree, but it's nothing radical. And I reckon a retro fit of the Ford engine would be harder

Though I'm sure you know that already.

The V8 in the car ain't dead yet and I like it, it has a unique deep turbine like sound and I reckon it (or the W116 engines in general...) has heaps of potential. But anyway, at the moment I'm just looking into getting an extra ratio basically to get that down low 'oomph' off the mark.

Mind you though, shifting into 1st at 60Km/h is quite fun - flatten the throttle and get SLAMMED against the seat
(and until the valve seals are done, nasty puffs of smoke )

 

[Mercules]

Yeah, I was taking the piss to tell the truth I will probably be looking for a 350SE myself for a project car

 

[Des]

Andrew, why not simply do a 350SE + for speed manual?

they are rare but they do pop up sometimes, or maybe 280S's and 280SE's with the manual box would also be suitable?

 

[Andrew280SEL]

Andrew, why not simply do a 350SE + for speed manual?

they are rare but they do pop up sometimes, or maybe 280S's and 280SE's with the manual box would also be suitable?

Yeah, I have actually thought about that and certainly like the idea...

It would sure be fun having manual behind this thing


The only thing I'd be concerned about would be what possible extra work would be involved...with the auto I thought that once it was attached to the engine, that would be it, pretty much. Set up the the oil dipstick tube, screw in gearstick etc.

But it's still worth a look I guess.

Yeah, I was taking the piss to tell the truth I will probably be looking for a 350SE myself for a project car

Yeah I thought you probably were

I was quite tired when I responded and post all kinds of things on forums when I'm really tired...

You're looking for a 350SE project car huh....do I sense Team W116 Car #3...

 

[WGB]

All the contemporary road testers were divided when the fluid flywheel 4 speed was replaced by the 3 speed with torque-converter.

The fluid flywheel 4 speed was more lively but apparently gear-changes were too rough for the US competition.

Hence the three speed with a torque-converter (Which theoretically allows first gear to be the equivalent of first and second in a fluid flywheel set-up) was considered adequate.

The problem is that a 3 speed works well with a big motor - just put in a 6.9 attached to it's usual 3 speed and you'll find it has adequate torque to not worry much about thjree or four speeds.

Then again my ML 500 has a 7 speed auto and it works just fine.

Bill