Thinking about doing this, unless it is to difficult - PeachParts Mercedes-Benz Forum

junqueyardjim · #1 09-08-2011, 08:40 PM

Guys, here is my problem. I put that late model 240D four speed behind my 617 Turbo. Runs great, but too much noise - it is driving me crazy, well unhappy at least. That is probably one reason they did not export the 300D with the four speed to the US. To much/many complaints about engine noise and reverberation. It is OK when the engine gets over 2200/2300 rpm. Then the impulses flow so smooth it is a delight. But between 35 and 42 mph, with the throttle open and pulling hard in 4th gear she is so noisy. It is quite loud in 3rd also from about 25 to 33mph. Above those speeds it is very pleasant. Now in the past this transmission suffered some damage along with the floor of the car. Something hit the bottom of the car ripping an 8 inch gash in the floor, breaking the shift mount which is attached to the floor and I suspect in the same incident broke one of the ears off the tranny that is designed the hold and insulate the exhaust from the car. One ear is completely missing. I do have the exhaust pipe mounted rigidly to the one ear, but it takes two ears. Here is a drawing of the transmission.

http://mb.ilcats.ru/part/class/1/ccode/F/cat/03G/type/716/subtype/210/group/26/subgr//vers//imgno/1

On "view" #5 you get a good look at the part with the two circular ears on the bottom. It is also part #5, and it looks like one ear is bigger then the other, but they are the same. Mine has the bigger ear broken off. That plate is really the back of the transmission, although there is an additional rear cover which has the mount for the reverse gear shift mechanism running through it and also contains the speedometer drive. It doesn't look like a real challenge to remove and replace the back cover. I want, rather need to replace that intermediate piece #5, along with new gasket on either side. So here is the question. Do you think it is feasible to change that plate, (make sure you look at view #4 also, it is the big piece in the center with no number and is rather crude drawing) with the transmission in the car? It is really the back plate of the transmission and it is probably built to accept either the end cover as shown or perhaps a transfer case or auxiliary. View #6 shows the reverse gear lever attached to the rear cover and extending through the back plate - the lever is #123 I think. If I do the job or send it out, do you see any other pieces I should replace? Please give me your best thinking on this. I don't like to get into stuff I can't finish, although time is not an issue. I like to order all parts at one time if possible. If Bajaman was around, I would be pulling it apart already.

lutzTD · #2 09-08-2011, 09:29 PM

just for reference, my noise disappeared when I traded in my last 4spd. It was recently rebuilt. I got a marked improvement before the rebuilt transmission when I installed a larger rear diff from a 126, the shaft mounts slightly lower due to the larger ring gear. I still feel the worn transmission was the main cause on mine. with the rebuilt trans and the 2.47 geared 126 diff it was an absolute pleasure to drive.

as an interim fix and reduce a lot of the noise with little trouble, I added qty2 1/8 thich washers between the 240D auto crossmemeber and the frame rail to lower the transmission. I also noticed the auto has a thicker tunnel insulator so look for places where the 4 spd might be hitting that.

cant help on the rebuild, I generally replace these rather than rebuild as they are pretty common and $75 at the PnP

junqueyardjim · #3 09-09-2011, 09:54 AM

Well thanks lutzTD. I appreaciate the info, might be able to use it, but I am not having a transmission or rear end noise. It is engine noise I need to reduce, but thanks anyway.

JB3 · #4 09-09-2011, 10:21 AM

The ears are part of the intermediate plate of the transmission case. You could remove the rear cover easy enough, but the ears are part of the next piece in, and it would be a little more complex to do with it on the car.

You will have to remove a bunch of snap rings ect from what I can remember to free the plate from the output shaft and counter shaft, and the Reverse Idler Gear shaft is actually mounted to/press fit in that intermediate plate facing inward, so you also have to do some work on the shifting mechanism and some finagling to remove the plate.

It would be much easier to do with the whole transmission out of the vehicle I think. Really the big PITA issue is that once all the bolts come off, the plate wont come off easily since lots of stuff is supported by it.

Im not sure, but the reverse idler gear shaft may be additionally supported by a bolt through the side of the case further forward. If you pull out this bolt, the shaft, and idler gear may pull out of the forward part of the case with the intermediate plate much easier, but you are basically taking the whole gearbox apart.

I had this same problem, and did the same thing you did, I had a piece of aluminum welded to the intermediate plate to make up the second broken ear, then bought new rubber insulating exhaust grommets that are supposed to fit in the ear.

Do you have the exhaust directly hard mounted to the remaining ear? If you do, then it would probably get much quieter if you re do it with a rubber mount.

junqueyardjim · #5 09-09-2011, 11:41 AM

Well thanks, dropnosky, I was thinking of PM'ing you because I thought you probably had the answer. Your thinking is pretty much in line with mine. Looks like it should be done on the bench, and then you might as well just weld a new ear on. I do have the exhaust tied to the one ear, with the rubber bushes, ect, but a certain engine speeds it really drones and rattles the windows and just sets up a nasty vib the reverberates through the sheet metal. It is bad from about 1800 to 2500 rpm if it is pulling hard, I can get away from it by downshifting, but I would rather not. I can see that the reverse gear lever going through that plate might be a real problem, let alone the two shafts with bearings and snap rings. I think I will try hard to buy another transmission. In the mean time I will just see if I can fix up some system to reduce that exhaust/engine power pulse vib. Let me know if you think of something.

whunter · #6 09-09-2011, 11:48 AM

Did you drain the transmission, and re-fill it with Dexron/Mercon III automatic transmission fluid?

.

junqueyardjim · #7 09-09-2011, 01:30 PM

Thanks Hunter, but I drained and refilled it with Mobil 1 10/30 engine oil.

TheDon · #8 09-09-2011, 01:35 PM

Quote:

Originally Posted by junqueyardjim

Thanks Hunter, but I drained and refilled it with Mobil 1 10/30 engine oil.

I'd drain that and put in some pennzoil synchromesh.

lutzTD · #9 09-09-2011, 01:36 PM

Quote:

Originally Posted by junqueyardjim

Well thanks lutzTD. I appreaciate the info, might be able to use it, but I am not having a transmission or rear end noise. It is engine noise I need to reduce, but thanks anyway.

since they are bolted together it is hard to distinguish the difference. I had the same drone and it came with the manual as I did not have that drone in the auto with the same engine. my above comments are what made it better for me. I assume this annoyance is a big part of why MB didnt make a 300 turbo 4spd, with the bigger ring, the lowered transmount and a rebuilt transmission I did not have the drone you describe.

t walgamuth · #10 09-09-2011, 02:01 PM

If you had the missing piece or could make a template for it I know a man who could probably weld it back on for you who lives and has a shop in Anderson IN. He is very reasonable on price too.

He'd do it with the tranny in the car too.

Did you upgrade your diff to a 307?

whunter · #11 09-09-2011, 03:56 PM

Quote:

Originally Posted by junqueyardjim

Thanks Hunter, but I drained and refilled it with Mobil 1 10/30 engine oil.

That is the wrong oil, and will cause excess noise.

Flush and re-fill it with Dexron/Mercon III automatic transmission fluid.

.

junqueyardjim · #12 09-09-2011, 05:30 PM

OK Hunter, but I am not having a transmission noise. At low rpm's I get engine vibes razzing on the exhaust system. Don't think Dextron would help that, do you? There has been some chatter on the forum as to what fluid to use to replace the old ATF stuff from early 80's and I thought the concensus was Mobil 1. I think they are about the same viscosity, (I think). Anyway, I will reread the Posts on the transmission lubricant and it doesn't take much, just is hard to get in there.

On Tom W's remark, I don't know if it could be welded in there in place. I would think the gaskets might burn up. That plate is aluminum and about 1/2 thick. It wouldn't take much heat and those gaskets would be toast. But of course I don't have the piece either, and finding one that might be close and could be modified is pretty far out thinking. Could have one made from scratch of course, I think a circular one could be fafricated. I also think some of the vibe is caused by the use of the light weight 240D flywheel, so some of it will never go away. I runs so good and sounds so good too, on and off the throttle - I just don't like the buzz in a Benz

t walgamuth · #13 09-09-2011, 09:58 PM

You should take it over to Mikes shop and let him look at it. He is a whizard with a welder. He reconstructed my aluminum wheel hub on my formula ford and it was broken into six pieces. He also reconstructed a cast iron ear on the back of my formula ford engine block without taking the engine out of the frame.

whunter · #14 09-09-2011, 11:44 PM

Quote:

Originally Posted by junqueyardjim

OK Hunter, but I am not having a transmission noise. At low rpm's I get engine vibes razzing on the exhaust system. Don't think Dexron would help that, do you? There has been some chatter on the forum as to what fluid to use to replace the old ATF stuff from early 80's and I thought the consensus was Mobil 1. I think they are about the same viscosity, (I think). Anyway, I will reread the Posts on the transmission lubricant and it doesn't take much, just is hard to get in there.

The ear needs to be replaced, or you can fabricate a wrap around bracket to replace it.

FYI:
The exhaust bracket is mounted through rubber isolates RE: attached pictures.

charmalu · #15 09-10-2011, 11:31 AM

My 85 300D has been sitting since Oct, but does have the 4-spd swap.

As I remember, in 1st and 2nd gear it is smooth all through the RPM ranges. but in 3rd is where I get the vibrations. over 3000 rpm`s it smooths out. and as long as I stay above 3000 in 4th, all is good.

I tried the washers of different thickness between the trans X plate, between the rubber mount and X plate, even tried to lower the center support bearing. at first it seemed the change helped, then after a little driving, I was back to the same problem. so I was up and down with washers trying to find the sweet spot. now Iam back to stock.

I am using the 2:88 Diff. and have ATF in the transmission.
All mounts are good clear back to the replaced Sub Frame/trailing arms bushings and Diff mount. new center support bearing and U-Joint.

Does seem strange, the 300D NA that has a 4 spd has no vibrations, but does use the 3:46 Diff. so adding the turbo and a higher Diff is the difference?
there is the 80+ HP increased to the 123HP .952 engine.

Charlie