Ken,
I would guess for 97% of the rear ends this is the case. The 1971-'72 Ford 3/4 ton
truck (I had a '71 new, still have a '72) the "slop" in the rear is almost an inch. When I
bought my '71 I questioned the salesman about the noisy "clunk" when the truck was shifted
from reverse to drive. To satisfy my concern, we started about 8 or 10 trucks with the
same engine/trans (360 V8/C-6 Auto) and all did the same thing. Gets a lot quieter when
the running gear is warm, but still, a heck of a lot of play. I have 135K on the '72 and
the rear end is still quiet, but still clunks when changing forward to reverse. The '71
was a standard rear end, the '72 is limited slip.
Depends on the manufacture of the gears I guess.
Russ
----- Original Message -----
From: "Kenneth Molloy" <ken@molloys.
To: <Diesel-RVs@yahoogro
Sent: Friday, February 08, 2008 1:49 AM
Subject: [Diesel-RVs] Re: Vibration when coasting.
: --- In Diesel-RVs@yahoogro
: <mredsel890@
: >
: > Ken,
: > When you say there should be no play in the pinion shaft. You
: should explain in a
: > forward and reverse manner. There is some "twist" play, but none in
: up and down, or
: > forward and back.
: > Russ
:
: You're absolutely right, Russ. There out to be just a little
: movement when you twist the pinion, but just a fraction of an inch --
: a few thousandths. If you marked the pinion housing and the yoke,
: then rotated the yoke, there ought not to be but about 1/16 of an inch
:
: Ken
:
:
: > ----- Original Message -----
: > From: "Kenneth Molloy" <ken@...>
: > To: <Diesel-RVs@yahoogro
: > Sent: Friday, February 08, 2008 12:26 AM
: > Subject: [Diesel-RVs] Re: Vibration when coasting.
: >
: >
: > : --- In Diesel-RVs@yahoogro
: > : >
: > : > Hi Phil and Mike,
: > : >
: > : > I really hate to be negative on mechanical issues as they can
: really
: > : > surprise you sometimes. It seems to me any competent shop would
: > : have already suggested replacing the U-joints when they saw zerks
: > : missing and a dry condition. Especially when they diagnosed bad
: > : pinion bearings. I too would change the u-joints and test before
: > : pulling the rear apart. You are talking lots of labor $ verses
: > : minimal labor $ to be sure.
: > : >
: > :
: > : This whole scenario reminds me of an incident which made it on
: one of
: > : the television programs a few years ago. A couple in a motorhome
: > : would be cruising down the freeway in Arizona when a pickup would
: > : pull up alongside and wave them down, telling them there was smoke
: > : coming from the rear end. The MH was then advised to take a
: nearby
: > : exit and take it to a shop where the mechanic rolled under the
: rear
: > : end and removed the differential cover, then came out with a
: greasy
: > : rag full of metal shavings he said came out of the rear end.
: > :
: > : The shop was able to locate a good used differential assembly for
: > : about $500, and when it came, they would install it. Several
: RVers
: > : had fallen into this same trap, and the television shop finally
: set
: > : up a motorhome with a TV camera directly above the rear axle, and
: > : then drove down that same stretch of the freeway. They caught
: > : the "mechanic" taking a greasy rag full of shavings under the MH
: and
: > : then opening it up and showing it to the RVer. Then the "used
: > : differential" turned out to be the original one after it was all
: > : cleaned up.
: > :
: > : The Arizona state police arrested everybody who was involved and
: when
: > : the differential was properly reinstalled, there were no problems.
: > : They had been victims of a scam.
: > :
: > : When I was a mechanic, I did a lot of rear axle work -- possibly
: > : because I was the only mechanic in the shop who owned a dial
: > : indicator. There should be NO END PLAY in the tail pinion! NONE!
: > : Depending on the rear axle manufacturer and model, the preload on
: the
: > : pinion bearings is usually set by torqueing the nut on the yoke
: to a
: > : certain value, which crushes a bushing on the shaft. That "crush
: > : bushing" has to be replaced every time the yoke nut is removed.
: > :
: > : If there were zerk fitting missing from the U-joints, that alone
: is
: > : good reason for replacing the U-joint. If you just screw in a new
: > : zerk fitting and grease the U-joint, you would be forcing every
: grain
: > : of sand right into the needle bearings!
: > :
: > : U-joint kits aren't very expensive, and the labor to remove the
: drive
: > : shaft, replace the U-joints, and reinstall the drive shaft
: shouldn't
: > : exceed 3 to 3-1/2 hours.
: > :
: > : More than 50 years experience as an automobile, airplane and RV
: > : mechanic have taught me that when you have a problem like this,
: look
: > : at the last thing which was done before the problem started. In
: this
: > : case, the driveline was removed for towing. Apparently there was
: no
: > : vibration before the driveline was removed, but now there is
: > : vibration! Bingo! Eureka! Problem solved!
: > :
: > : I still believe the problem will end up being that the two yokes
: on
: > : the ends of the driveshaft are not aligned in the same plane.
: That
: > : will very definitely cause a vibration.
: > :
: > : Ken Molloy
: > : '94 Allegro Bay 37' MH
: > :
: > :
: > :
: > : ------------
: > : Off-topic posts will be removed.
: > : Please sign with your name (real or online name) and include the
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: > :
: > : To unsubscribe from this group, send an email to
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: > :
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: > :
: > :
: > :
: > :
: >
:
:
:
:
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