After reading through this thread a couple of thoughts occured. First was to slowly rotate shaft with a dial gauge to check how much if any runout present at front, carrier bearing area and around rear. This test was done years ago with engine running and wheels turning with a piece of chalk held to see if chalk line was continious around the driveshaft at different points. Any runout at any point would indicate driveshaft was running off centre or bent of course and would cause the vibration easily. Next was the old ideal of two hose clamps installed on driveshaft to see if any improvement was made by various positioning of them. This would also compensate for out of balance flex disks but that senario is kind of unlikely as I think you replaced them and drove car before problem. Tedious but at least things to check and both pretty common tests. If the rear sleeve bearing in the transmission is not sloppy it would eliminate the actual transmission as a suspect I believe. Logic says it has to be something that has changed. Needless to say the disks are phased properly? Just though I would throw the last item in as did not see anyone mention it. These types of problems can be very frustating to have and find sometimes. The more information you quote the more it sounds like something making the driveshaft run off centre or a balance issue perhaps contributed to by something like a flex disk. In order to really find a problem in my experience you have to divide it up. Wonder if an on the car tire balancer has enough power to rotate a rear wheel and the driveshaft with the transmission in neutral up to vibration speeds? Better than the dyno test I believe if a guy could find someone that had an old one around. I would have to think a little about this prior to doing it but if ancient memory serves me they were pretty powerful and the additional load may easily be within their power range. This would absolutly eliminate or condem something and is the type of test I like but not always possible unfortunatly. Guess one could drive car into vibration speed and push clutch in and put transmission into neutral and if vibration still there you have narrowed it down as well. There is no senario that comes to mind to really indicate the transmission or even an internal fault other than the rear bearing being very sloppy possible with the transmission that I can think of. If you can solve this it will help some others perhaps as well. If the effect is so severe that it makes images in the mirror fuzzy and that is possibly a harmonic of the primary vibration it means the primary vibration frequency is very strong and should be found for other reasons other than the annoyance.

Interesting that this thread would resurface today since it is the 2nd anniversary of intalling a manual in my wagon. And no, after two years and about 40thousandsomething miles, the vibration issue has not been resolved either. But interestingly enough, the vibration is only marginally worse than it was in the beginning.

FWIW, revving the engine (both in neutral and with the clutch disengaged) to the rpm where the vibrations occur does NOT duplicate the vibration. It is definitely not the flywheel causing this vibration.

I'm confident my problem comes from a badly worn transmission which hopefully will be resolved in the not-to-distant-future when I install the five-speed I have in inventory.

cool
 

a fiver. the ultimate combo.

i am betting it is not the tranny though. if it was that bad it would surely leak out the back seal.

tom w

Sorry to hear that R Leo still has the vibration issue, but its nice to hear that the car added 40K miles already without killing the tranny.

I was thinking about why the vibration occurs only in high gears under load, and I came up with a hypothesis of sorts (btw putting it in neutral to isolate the drivetrain vs trans wont help, unfortunately. Also, I thing the driveshaft itself is fine ie no runout).

One of the things that all our conversions have in common is the fact that we all fabricated the rear trans mount out of something. Mine is a stock auto trans mount/bracket bolted to the original location with a 5/16" thick 2" wide ~9" long steel bar that functionally extends the manual tranny to the length of an automatic. Other variations and this one all include eyeballing the stock location of the tranny.

In any case, firstly there is the problem of getting the height of the transmission right and secondly is it possible that under load, the transmission moves too far over causing the driveshaft to rotate off center? In low gears the drivetrain is never at the same speed for very long, thus making the vibration imperceptible; if you load up the drivetrain in low gear you change its speed as well since the car actually accelerates.

I will have access to a euro 5 cylinder 4 speed this weekend or next and plan to swap out the mount to test this.

Any thoughts?

it is possible. but i think a little misalignment wouldnt be much problem. but using a factory mount is a very good idea.

and the original poster never stated if he removed the motor mount steel tab that is on the front of the cross member on a 240.

or maybe his car wasnt a 240 to start with. cant remember

tom w

I thought about this same thing (FWIW, my rear mount is fabricated from a 240 manual rear crossmember) and a couple of months after the swap was complete, put the car up on stands, pulled the driveshaft separated the stub end and directly bolted it, without the flexdisk, to the tranny output spider.

I bolted-in an old center support bearing hoop and used a piece of pipe slipped over the stub shaft to 'extend' the driveshaft axis into the plane of the hoop so that I could determine visually if the driveline was centered in the hoop. While not a perfect tool, the stub a least gave me a pretty good reference line to use in determining if the driveline was misaligned at the back of the tranny.

Vertically it was really close but, it wasn't centered horizontally so I removed the crossmember and reworked the outboard mounting holes so that the output shaft was now centered.

After reassembling, I could not detect any difference in the amplitude or frequency of the vibration.

About 8-10 months after completing the conversion, I bought a running but wrecked 240 manual parts car and had the opportunity to drive it around some
before pulling the 4-speed tranny (there were no unusual vibrations...etc). Upon pulling the transmission, the first thing I noticed was that the outbut shaft on this tranny was 'tight' compared to the one in the wagon. The wagon's shaft almost feels as if the spud nut holding the spider is loose (it isn't)...so, the looseness must be in the splines on the output shaft but only an autopsy will determine this.

Remember, the donor vehicle was in a boneyard and, her center shaft support consisted of one seized bearing and a hoop-shaped piece of steel...there wasn't a scrap of center support rubber to be seen and it was apparent that the car had been driven that way for some time. BTW, it was in the yard because it had been rear-ended, probably while parked on a street (the LR tail light was under the rear window). I only bought it because, at the time, I thought that 4-speeds were ultra RARE.

Putting that 'new' 4-speed in the wagon became academic after acquiring the Euro 240 with the five-speed...however, it's destined to soon be the replacement tranny for the Euro....if I can EVER finish my a/c job on the SDL.

I'm a relative newbie here, and I'm still learning things every day, so 'All due respect'... but what are you doing in that RPM range in 3rd and especially 4th gear... I think you are 'lugging' yer engine, simple as that.

All of my readings here lead me to believe that you should never be below 2k rpm in the upper gears. Since I put on oversize tires, I try to keep it above 2200 rpm.

I usually run my engine up to at least 4k rpm before shifting, so when I catch 3rd and 4th, I'm well into the 2k rpm range.

Just for fun, I tried running in in 4th gear in that rpm range... and it vibrated (among other things) my rear view mirrors.

Whats your rear end ratio and tire size?

EDIT- I've got an N/A, and know next to nothing about turbos, so if I'm totally off base here, please be kind.

I don't consider drifting (holding speed w/minimal throttle, not the sideways kind) on level ground at 40 mph in 4th gear to be 'lugging' the engine. Under minimal load, a vehicle equipped with an automatic will shift into 4th gear by that speed, why should the manual be any different? Additionally, you must apply a significant amount of throttle in order to downshift the auto from 4th to 3rd (at least on my 300D you do). No vibration is experienced during that period.

i agree
 

under light throttle if the engine is pullling smoothely in top gear at 20 is fine. running to 4k on every shift is too high unless you are needing maximum or near acceleration.

imho

tom w

I am fortunate indeed that I drive on the hiway 98% of the time. I only stop for toll booths:mad: fuel:cool: and boobies;) So when I'm merging back on the hiway, I 'give her hell'.


FWIW - Using my tire/rear end info (I'm pretty sure I've got a 3.49 rear end)... I don't think yours are listed. Just for clarification are these the approximate speed ranges in 4th gear?

mph = (rpm x tire diameter) / (gear ratio x 336)

31.4 mph = 1400 * 26.3 / 3.49 * 336

42.6 mph = 1900 * 26.3 / 3.49 * 336

My wagon has the stock 3.07 and is running Michelin P205xR14s...w/excepton of the manny tranny, basically stock stuff. Turbos have taller final drives.

I have no idea if you answered this yet: Is the speedo still correct after changing the tranny?

Nope, it's off (reads fast) by almost exactly 10%...actually, I think I might have covered this in the original tranny swap thread (FWIW, any references to the wagon's speed or economy have been corrected).

A visit with the local VDO gurus informed me that there are supposedly only three different speedo head gearings for the 123 chassis and I'm guessing that a speedo head out of a n/a car might be close enough calibration-wise. The '81 300D that's out at the farm right now has a good cluster...one of these days I'll swipe the speedo out of it and give it a whirl.

i dont see how
 

changing from auto to manny could result in 10% error.

some difference would be expected but not nearly that much.

did you check it for accuracy before the swap?

tom w

Yes I did...it was startlingly accurate on both miles and speed.