I'm constantly impressed by the expertise on this board, so let's see who can come up with the right answer first. We'll eventually have a winner as I intend to track this one down, no matter how long it takes.

PROBLEM:

Between 2000-2500 RPM in first gear only I get a moderate shudder from the rear of the car under heavy acceleration, almost like it is winding up. I don't get it in 2nd at all, or even in 1st at the same RPM's or speed if I'm not under heavy load. It sometimes feels like the vibration is coming from the left side of the car, but I can't swear to it.

Car is an '82 300TD with new rear subframe bushings, control arm bushings, diff mounting rubber, shocks, rear springs, CV axles (rebuilt Advanced Auto chepo's), new tires, professionally balanced, with a 4-speed manual swap, new carrier bearing, new front and rear flex disks. I have NOT replaced the u-joint, as it felt tight when the driveshaft was out. I had the diff out of the car at one point and drained and replaced the gear oil. Nothing looked loose or broken.

I'd be skeptical of driveshaft vibration as the culprit (see RPM comment above), but for what its worth, I did not have it balanced with the manual swap as I located a euro front driveshaft half that slotted right in with no modification, thank you very much. Doesn't vibrate at similar speed/rpm if it isn't under load.

So, brain trust, what should I check first? The el-cheapo CV axle? Diff pinion? U-joint? Alien interference?

Thanks!

Does this auto have a vibration damper on the drive shaft? Is the shaft two piece and if so were the halves matched and correctly lined up? Was the flywheel balanced with the crank or is this a factor? How old is the pressure plate?

Relative to changing all these suspension components and changing the transmission when did the vibration first begin? Is it out of order for someone who knows nothing about a 123 to be asking questions? Did the aliens probe you?

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84 300SD
85 380SE
83 528e
95 318ic

That shudder I bet is your center support bearing.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

The solution to a similar vibration that I had was orientation of the carrier bearing on the driveshaft. The original u-joint had a slight wear detent and would cause a vibration under load.

The solution, short of u-joint replacement, was to feel for the "direction" of the detent and install the driveshaft so that the "up-and-down" motion of the rear portion didn't go "against the wear".

Hopefully, you get the drift of what I'm trying to say.

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Sam

84 300SD 350K+ miles ( Blue Belle )

I think some not to massive vibration is normal in a 617 with the stick conversion. The five cylinder configuration gives a hoppy vibration and when accelerating you'll get a bit of quiver...perfectly normal imho. I've done 5 or 6 manual conversions over the decades.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I have two 5sp, 617 conversions and one does it, one doesn't. I have tried EVERYTHING! First motor mounts and tranny support, then new center support, re-balance driveshaft, new flex disc, new half shafts, and even new differential. Finally, I just swapped out the Getrag 717.400 and still at about 1800 rpm's I get the vibration and really loud sound. Tomorrow I am going to swap out all four wheels and tires, after that I'm lost.
The other one does not have the problem.

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In all gears, or just in first?

What are the rear axle ratios on these cars?

All gears under light load, always at around 1800 rpm's. Original diffs swapped for 2.88's

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I had a similar issue when I swapped the om617 into my 4speed 240D.

Slight vibration at a specific RPM. The 240D doesn't have a tach so I can't tell you if it was 1800, but it happened around maybe 45mph in 3rd, and 60ish in 4th. Happened under light load as you describe.

I had the drive shaft professionally balanced and the carrier bearing/rubber mount replaced. Problems solved.

I had replaced everything rubber beneath the car. Swapped out diff's and transmissions before having the drive shaft balanced. As it didn't seem to be drive shaft vibration which I would have expected to be more violent or increase with rotational speed.

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Old Blue - 83 240D 6 speed manual trans, OM648
Green Machine - 2001 Europa G500
87 300SDL Bought on Peachparts. Low-ish miles..?

Family Truckster - 2012 VW Touareg TDI

Patchouli Wagon - 2004 E500 - SOLD
333k mile 97 BMW 750il V12. - SOLD
The Californian - 85 300TD - SOLD
Daily Super Sedan - 03 Audi S8 -SOLD

Yeah, I don't want to overstate the behavior. I took it out this morning and tested it. The vibration/shudder only happens if I come close to dumping the clutch at 2500 or 3000 RPM and flooring it. Releasing the clutch more gently into lower RPM's and letting the engine torque do the work results in no vibration. Still, I'm curious as to what the heck is vibrating ...

I'm going to try this and report back.

HAAAAAAPY to take that Getrag off your hands. Let me know if you want to sell it!

More advice the merrier.

Ok, These cars are sensitive to rear position. The rear end gets a lot of twist. If your wheel bearings are failing, heavy acceleration would load up the drivers side and cause it to drone.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!