vibration at 2800-3300 RPM

Brorag · Brorag's Garage

'87 cab
G50 transmission
new motor/tranny mounts didn't fix it
all gears
goes away when clutch engaged--if above 3500 RPM, vibrates when engine speed slows thru 3400 to abt 2800 RPM
present in neutral and when stopped with clutch depressed
Haven't spotted anything touching
I've run out of ideas...wot am I missing?

EdRogers · 09-03-2018, 03:33 PM

Sounds like it is somewhere between your pressure plate and your fan pulley. Probably not what you want to hear.... check the alternator and belt assembly first?

freeform911 · freeform911's Garage

Was just a tread about the same problem. Turned out a spare tire was causing a frequency.
Check to make sure your spare is tightly held down .

DRACO A5OG · DRACO A5OG's Garage

Quote:

Originally Posted by Brorag

present in neutral and when stopped with clutch depressed

It vibrates under load up and down in RPM range in gear until clutch is at 3500 RPMs, also vibrates coasting in neutral/idle and at stop/idle?

Are all cylinders firing? What is your idle speed after she is hot? Remember our Tach starts with 400 RPMs

HaroldMHedge · HaroldMHedge's Garage

This maybe the infamous G50 rattle.

Quote:

Originally Posted by imcarthur

Above from Excellence. Below from Tech article.

Ian

from G50 Rattle

HaroldMHedge · HaroldMHedge's Garage

Here's another TSB on the shifter rattle.

Quote:

Originally Posted by MBEngineering

HI -Ryan
You could try this, I posted on hear,

Engine vibration at 3000rpm - Pelican Parts Forums

and this below is for your education purpose only,

with this you should be able to make it a little quieter.

regards mike

from Is a chattering sound normal starting out in 1st gear? '88 Carrera

Brorag · Brorag's Garage

seems to be temp related
back to rebuilder--shim the tranny mounts.

Brorag · Brorag's Garage

I think I finally found that vibration. Not the shims. Back after rebuilder shimmed mounts with same issue--took prolonged drive with mechanic and was able to replicate by turning A/C on/off. Still cools, but greasy oil around compressor/clutch and under deck lid. Recent recharge to top off, though was still cooling.
With A/C on, able to replicate watching engine/compressor; belt vibrating at ~3K RPM-will snug belt, but oil is a giveaway. Current system is 134a replacement, so looking for compatible compressor/clutch--is there anything out there more better/efficient than Sanden 507 or Denso 471-0124?
update--tightened belt; no joy.