1975 300d and 1977 240d 4 speed swap?

[Deweksan]

Hey guys, i had a question about manual transmissions. I currently have a 1975 Mercedes 300d with a 4 speed automatic trans that will not drive over 15mph. I want to do a 4 speed manual swap or 5speed if possible, I found a 1977 240d with a 4 speed manual trans at the junk yard and was wondering if that will fit into my 1975 with little to no mods? Or if any one has any sources where there are 4 speed manuals that can fit my application id be happy if you shared them . I have searched for far and wide, but no go. Thanks-!

[cooljjay]

It requires a lot of work, and a lot of part searching....ideally, I would just fix your auto....What are the symptoms of the transmission? Have you done any work on the transmission yet?

[Deweksan]

Originally Posted by cooljjay

It requires a lot of work, and a lot of part searching....ideally, I would just fix your auto....What are the symptoms of the transmission? Have you done any work on the transmission yet?

Hmm ok... the auto tranny has just had its oil changed. When I press the gas down in drive, it revs high and transmission barely catches and it begins to pick up speed. At one point I think I heard metal grinding. When it gets up to 2nd gear it will increase in speed very steadily at a high rev, then when it wants to hit 3rd gear it slips into a neutral cruise. I prefer to just get rid of this transmission so I wont have to deal with another issue popping up and waste money.

Ive been searching for a 4 speed. I found a 1977 w123 at a junk yard with a 4 speed but I didn't pull it, because I didn't know if a w123 tranny would fit direct into my 1975 w115. Thanks for responding, sorry for my late response been busy!

[ScooterABC]

Others will know better than I, but I strongly suspect that a later automatic is a bolt-in conversion, where as a conversion to manual transmission is a lot of work.

[junqueyardjim]

Well I think any automatic out of a W123 will work in your car if it is a working transmission. But going with that 4 speed stick is really a wonderful way to go, though it is a bit more work then just sticking in another automatic. But you must have all the parts to do the job right. Ideally you should have the donor car right there with you as you do the swap. But make a list of what you need and follow through on it. You will need everything off the donor car that makes it a 4 speed. Five speeds are so rare as to not be worth talking about. But you need from the donor car the transmission, clutch and bell housing. You will need the clutch and brake pedal assembly. You will need the clutch hydraulic parts and lines which is pretty simple. You will need the flywheel off the donor. If it is a 240D donor, it will be the light weight flywheel and it is useable on the 300D. If you are really lucky and the donor is a 300D, then you will get the heavy flywheel which is ideal. You will need the transmission crossmember from a 240D automatic. You should also use the differential from the donor, and then also the speedomometer if you want the speedometer to be correct. Then the front section of the driveline will probably need about 4 inches added to it. You should use new flywheel bolts when you re-install the flywheel, They are expensive. And while you have it apart you should have the clutch disc, pressure plate and flywheel examined, and replace and resurface as necessary. It is a lot of work and I would NOT do it on a rusty junker. But if the body is nice, it really makes a nice car, though they are just a little bit noisier inside. Mine is noisey when cold, but very comfortable as to sound level when warm. So what you should do is really check the donor car and see if everything you need is there. It is also possible that the drive shaft front section from the donor might be the correct length. Well now I see you plan to put it into a W115 which is a little different but not much. You won't be able to make a direct swap on the dash/speedometer but it will work. Is your 75 300D worth the work/effort.

[Deweksan]

Originally Posted by junqueyardjim

Well I think any automatic out of a W123 will work in your car if it is a working transmission. But going with that 4 speed stick is really a wonderful way to go, though it is a bit more work then just sticking in another automatic. But you must have all the parts to do the job right. Ideally you should have the donor car right there with you as you do the swap. But make a list of what you need and follow through on it. You will need everything off the donor car that makes it a 4 speed. Five speeds are so rare as to not be worth talking about. But you need from the donor car the transmission, clutch and bell housing. You will need the clutch and brake pedal assembly. You will need the clutch hydraulic parts and lines which is pretty simple. You will need the flywheel off the donor. If it is a 240D donor, it will be the light weight flywheel and it is useable on the 300D. If you are really lucky and the donor is a 300D, then you will get the heavy flywheel which is ideal. You will need the transmission crossmember from a 240D automatic. You should also use the differential from the donor, and then also the speedomometer if you want the speedometer to be correct. Then the front section of the driveline will probably need about 4 inches added to it. You should use new flywheel bolts when you re-install the flywheel, They are expensive. And while you have it apart you should have the clutch disc, pressure plate and flywheel examined, and replace and resurface as necessary. It is a lot of work and I would NOT do it on a rusty junker. But if the body is nice, it really makes a nice car, though they are just a little bit noisier inside. Mine is noisey when cold, but very comfortable as to sound level when warm. So what you should do is really check the donor car and see if everything you need is there. It is also possible that the drive shaft front section from the donor might be the correct length. Well now I see you plan to put it into a W115 which is a little different but not much. You won't be able to make a direct swap on the dash/speedometer but it will work. Is your 75 300D worth the work/effort.

I think its worth the effort so far since I plan on keeping. Later down the road a v8 or different diesel engine swap as well as biodiesel conversion is in my mind, but Im talking several years down. This may be a car I want to keep and pass on to my future daughter or son.....Anyway thanks for the replies I really appreciate it!

I have another question(s), during this transmission swap will I be running into ECU or some sort of computer problem? Or does the transmission run off a different module? Will I need to mess with any computer component or is it just a simple swap? Thanks again!

[Rocket99]

Originally Posted by Deweksan

Hey guys, i had a question about manual transmissions. I currently have a 1975 Mercedes 300d with a 4 speed automatic trans that will not drive over 15mph. I want to do a 4 speed manual swap or 5speed if possible, I found a 1977 240d with a 4 speed manual trans at the junk yard and was wondering if that will fit into my 1975 with little to no mods? Or if any one has any sources where there are 4 speed manuals that can fit my application id be happy if you shared them . I have searched for far and wide, but no go. Thanks-!

it bolts right into any W123. I got every thing necessary at pick n pull for less than $300 on a sale day.

YOu will have to have the driveline cut shorter by about 3.5 in. A good driveline shop can do that.

Its an easy conversion. mercedes makes it so the stuff bolts right in.

The 240D flywheel works just fine.

[ScooterABC]

I thought you also needed the flywheel from the manual transmission donor car... no?

[sassparilla_kid]

Things needed, pedal set, manual car flywheel, shifter & linkages, pressure plate/church disc, manual trans, and probably a different trans crossmember and driveshaft length might need changing

[unkl300d]

1976 240D with 4 speed manual trans at local pik n pull now...... FYI

The conversion has been done. Search the archives.