'72 450SL: 4 or 5 speed ??

[Gregy]

I own an american 450 SL '72 (badged 350SL) with a 3 speed gearbox.
Is it possible to switch to a 4 or 5 speed box?
And if so what do I need ?

Thank you
greg, Belgium

[kip Foss]

Gregy,

Are you talking about a 4 speed manual or automatic transmission? I have a 350 slc Euro model with a 4 spd. manual trans. I bought it with the idea of putting it in my 450 slc which now has a 3 spd. auto trans. If you are talking about installing a 4 or 5 spd. auto trans. I can't tell you if it will work.

[Gregy]

Auto. trans. please.

The 4-spd automatic trans in the 380SL and 560SL won't bolt up to the 4.5 engine - you'd need to swap either down to a 3.8 engine or up to a 5.6 engine to use the 4-spd. There's some info on this page (http://www.carcentric.com/MB2MBswap.htm) about what that involves, but it's only applicable to US cars, engines, etc. I have no idea what's available in Belgium - maybe somebody at http://www.garage107.com/index.php could help.

The 4-spd automatic was my original goal with Ludwig, but I ended up swapping the engine to accomplish that, then this, then that, . . . see the link below to get some sense of how far you can go afield without even trying.

5-spd automatics are even newer, so I doubt they'd work with the early engine, either, but I have no data to base that opinion on.

[Gregy]

Thank you for all the information. I would love to put a 5.6 in it. But what to find the correct parts...and the work...

But I ll submit all your print outs to my garagist...I'm wondering his reaction ;-)

ciao

[yeldogt]

Do you want to do this for better fuel use or for top speed?

You would have to use a LOT of fuel - even at euro prices to make any swap work.

I spent many happy hours in a US 72 450 -- it was a great car. I loved the looks with the short bumpers, and it was simple - manual AC / windows. In fact in many ways nicer to drive than my 560SL.

The early 4.5 motor W/O cats had almost the same specs as the 5.6 motor of the late 80's.

The lighter weight of the early cars especially at the front plus the 3 speed made them fun to drive in the hills of Pennsylvania - the 560SL is always down shifting.

Now I would think top speed driving would be something else -- but I do think it was still only a 3 speed in Europe in 1972 -- correct?

Top speed (or gas mileage while cruising in top gear) wouldn't be affected by a transmission swap because the top gear is always 1:1.

What's different is the acceleration from a stop if 1st gear is used - BIG difference then. If you don't put a 4-speed AT into 1st, though, it'll automatically start in 2nd, making acceleration about equal to the '72 450SL with 3-speed AT.

[Gregy]

My 450 '72 is an american version , badged 350 SL with a 4.5
In Europe the 350SL was a 3.5, I believe also with a 3 AT.

The thought was first to have better accelerations with a 4 speed. But secondly to consume less in 4th, as I thought that a 4 speed had also a lower ratio in 4th speed ( called overdrive), so that that RPM was lower. Because at 160km/h my RPM is about 4000.

[Gregy]

Now the question...

Can I put a 4 speed AT on my original 4.5 engine ?
Or did a 4.5 exists with a 4 AT?

PS: Thank you guys for all your replies and helping each other to enjoy and learn more about our devine car and hobby. ;-)