4-speed conversion humming/vibration solution
 

I have been working on fixing my humming after my 4-speed conversion on my 300cd. I read before that lowering the rear mount on the trans has fixed it. My question is how much did you have to lower it to fix the problem.

I have lowered about 3/4 inch so far. It has gotten better, but not completely fixed yet.

3/4" is a LOT. Personally, while I'm hopeful that getting the driveline perfectly straight will help, I don't think that it is the only cause of the vibration problem. I think that this is why we see a few euros with that balancer thing on the back of the tranny.

1/8" washer for me give or take. High torque, low rpm buzz? Are you sure the DS is straight?

[edit]

What about flex disks? Did you replace them?

i added 3 washers to mine 1/8 thick when I added 4 it started a different vibe. the buzz i have now at low rpm high load Ive decided to live with. the balancer is on SD's, but it seems like a lot of work to get one off at the pick and pull. maybe when I have a full day to remove one ill try it

What? all SDs have a balancer?

all the ones Ive seen in the pnp had them

Well then, looks like I've gone too far.

a friend of mine swapped a 5 spd into his 4 spd Euro 300D and did away with the balancer on the DS with no ill effects.

if possible could you get a picture of the rubber trans mount on your buddy's euro 300d? My wager money is that it is a special part.

Its not, its a stock heavy duty auto mount. The X member on a proper 617 has 4 bolt holes not 2 and is wide enough to allow the proper mount. But what he said only got to further prove the point that I think the humming is from poorly aligned DS.

so the 240D auto cross member is not the same as the 300D euro 4spd cross member? the 240D cross member I have fits perfectly with the heavy auto mount that came off of my 300D auto.

A 123, 240D, four speed manual has a 2 bolt cross member and there are bolt holes for the "4 bolt CM". Five speed boxes use the "4 hole CM" as well, also, the auto tranny cars (616&7). The Euro 300D stick has the 4 bolt mount as Winmutt said.

Sorry, cant get pics

agreed but...... the 240D auto has a 4 bolt crossmember that fits in the four holes in the frame. it uses the two front holes from the 300D cross member and then I moved the 300D rear hole clips to the 2 hole forward of the 300D front holes. then the rubber mount lined right up, except I had to space the crossmember down by 3/8 with washers

pics of 240D auto 4 bolt cross member on 300cd 4spd
 

here is the 4 bolt cross member from driverside

I'll buy the idea that the ds isn't aligned properly. I am going to see if my broomstick is still straight tomorrow and try to see if it isn't lined up right.

Is there a way to rig the auto x-member to work with the manual? I haven't looked at it yet, but has that worked for anybody else before I kill time playing with it?