300cd stick conversion driveshaft question - PeachParts Mercedes-Benz Forum

t walgamuth · #1 04-17-2007, 11:35 AM

we are getting ready to put the four speed in the 300cd. now i looked and my automatic sitting in my garage (from a 240 i think) is longer than the stick i am planning to put into the car. the figure i have seen here is 4", i believe. my question is is the different lengths taken in the front half of the two piece driveshaft? i am thinking they always put the center bearing in the same place.

now the front driveshaft from a 240 automatic seems like it might be about the right length for the 300cd with the four speed behind.

can anyone offer specific information?

i am hoping to avoid the expense of haveing the driveshaft lengthened. and the worry of them not getting it right.

hmmmm the coupe is a shorter wheelbase too. is that 4"? so i am betting that distance is taken from the rear half of the driveshaft. and if i mix and match the front and back from different driveshafts i will probably have a vibration.

the other conversions i have done have involved being able to just take the parts off one car and switching them to another.

tom w

dalek · #2 04-17-2007, 01:11 PM

I believe that it will fit; AFAIK Mercedes was not like other makers and would make different driveshaft ends and that would require different transmissions tailshafts and differentials. About vibration, I thought the center bearing would keep one driveshaft from annoying the other one. In fact, when I do find a MT Diesel Mercedes I plan on snatching the very same parts.

t walgamuth · #3 04-17-2007, 03:49 PM

it has been my understanding that the ds are balanced as a unit thus separating one you must mark the position to keep the balance.

tom w

Old300D · #4 04-17-2007, 03:54 PM

Quote:

Originally Posted by t walgamuth

it has been my understanding that the ds are balanced as a unit thus separating one you must mark the position to keep the balance.

tom w

I'm not saying what you say is not accurate, but I've swapped front and back shafts with no vibration issues. The key is to line up the flex discs, just like aligning universal joints.

truckinik · #5 04-17-2007, 03:59 PM

Quote:

Originally Posted by t walgamuth

we are getting ready to put the four speed in the 300cd. now i looked and my automatic sitting in my garage (from a 240 i think) is longer than the stick i am planning to put into the car. the figure i have seen here is 4", i believe. my question is is the different lengths taken in the front half of the two piece driveshaft? i am thinking they always put the center bearing in the same place.

now the front driveshaft from a 240 automatic seems like it might be about the right length for the 300cd with the four speed behind.

can anyone offer specific information?

i am hoping to avoid the expense of haveing the driveshaft lengthened. and the worry of them not getting it right.

hmmmm the coupe is a shorter wheelbase too. is that 4"? so i am betting that distance is taken from the rear half of the driveshaft. and if i mix and match the front and back from different driveshafts i will probably have a vibration.

the other conversions i have done have involved being able to just take the parts off one car and switching them to another.

tom w

The coupe, and sedan are the exact same wheel base. The only differences are in the length, of the doors. The coupe, has one big long door, on each side, as opposed to two smaller ones. That, is the only difference in the overall body of the cars aside from the windshield, and rear glass, being at a slightly shallower angle. Anything mechanical, as far as driveshafts are concerned will be the same from sedan to coupe.

R Leo · #6 04-17-2007, 04:26 PM

Quote:

Originally Posted by truckinik

The coupe, and sedan are the exact same wheel base. The only differences are in the length, of the doors. The coupe, has one big long door, on each side, as opposed to two smaller ones. That, is the only difference in the overall body of the cars aside from the windshield, and rear glass, being at a slightly shallower angle. Anything mechanical, as far as driveshafts are concerned will be the same from sedan to coupe.

Not so.

The W123 wagon and sedan have a 2795mm wheel base; the coupe's wheelbase is just 2710mm or, about 3.5" shorter. The coupe's driveshaft is correspondingly shorter too.

Ref.

winmutt · #7 04-17-2007, 04:30 PM

4" that might be just short enough to use a stock 240d front hald drive shaft

R Leo · #8 04-17-2007, 04:36 PM

Quote:

Originally Posted by winmutt

4" that might be just short enough to use a stock 240d front hald drive shaft

I'm not positive but, I believe that the difference in the coupe's length is all behind the center driveshaft support.

bgkast · #9 04-18-2007, 03:51 PM

The 4" shortening comes out if the front part of the drive shaft if you are using the drive shaft from a 240D

Sounds like you should confirm that the coupe has a shorter rear drive shaft, then have a 240D driveshaft cut down 4" (or find a stock front shaft that is about 4" shorter than the 240D shaft) and have the new front and old rear balanced as an assembly.

truckinik · #10 04-18-2007, 05:08 PM

I don't get it, why not just find the correct stick shift driveshaft, for the car, and call it a day? Make some calls, check the net, they're out here, and available, just find one...and be done with it.

#11 04-18-2007, 10:24 PM

Because the 300D with a manual tranny was never sold in the USA. The ones that are here were owner imported as Grey market cars from Europe. To find a manual tranny 300D at all is extremely lucky.

In the USA, there are probably 500 normal (automatic) 300D's for every one 300D that was imported with a stick.

t walgamuth · #12 04-18-2007, 11:26 PM

i have never seen a manual tranny 300cd....

but there is one in the oven right now!

i talked with my indie today and found out that he has been mixing and matching my driveshaft halves in the other engine swaps i have done (i thought he had been swapping the entire driveshaft.) so the individual halves seem to be balanced... so far at least.

so i have at least three mb driveshafts from cars i have parted out so hopefully i will have what i need without cutting anything.

thanks for all the comments guys!

tom w

bgkast · #13 04-19-2007, 03:27 PM

Quote:

Originally Posted by t walgamuth

i talked with my indie today and found out that he has been mixing and matching my driveshaft halves in the other engine swaps i have done (i thought he had been swapping the entire driveshaft.) so the individual halves seem to be balanced... so far at least.

Probably just luck, just like how the Flywheel/crank are balanced as a unit but some Flywheels end up neutral. The two driveshaft halves are definatly balanced as an assembly at the factory and at driveshaft shops that know MBs.

This is the place I had my shaft done: http://www.driveshafts.com/pages/mercedes.html Just so happends that they are 5 min from my office.

Old300D · #14 04-19-2007, 05:11 PM

Driveshaft balance is WAY over-rated. There just isn't enough mass far enough away from the center of rotation, rotating fast enough to cause an issue. 4000 rpm is slower than most. More important is lining up the flex discs -- that will cause the vibration. I'm not saying a drive shaft can't be out of balance, but it's not the issue some think it is. Just my opinion, so don't go crazy....

t walgamuth · #15 04-19-2007, 05:27 PM

thanks guys. i agree with both of you.

we will go ahead and line up flex discs and hope for the best.

tom w