| Final Drive Question [message #280643] |
Wed, 24 June 2015 14:01  |
biggreen
Messages: 347
Registered: June 2011
Location: Northeast Florida
Karma: 1
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Replaced my stock unit with a Jim K. 355 a few years ago. Running the standard gear oil that was recommended in the installation instructions. I had read that it will whine a while until it breaks in. It has been about 500 miles (I know, I know) and it still whines on deceleration. Is this normal enough? Should I change the gear oil to a synthetic, as I have read on this forum? Thanks
77 Ex Palm Beach 403
R.D.
Northeast Florida
77 ex-Palm Beach 403
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| Re: Final Drive Question [message #280655 is a reply to message #280643] |
Wed, 24 June 2015 15:45  |
Gadabout
Messages: 124
Registered: March 2013
Location: Edmonton
Karma: 2
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Whine under deceleration may indicate the coast side of the gear has not yet broken in or has a bit excess backlash .
Most builders will try to optimize the drive side and this is were 95% of the 500 miles will be. Your coast whine may go away after a fluid change and some more miles. If not , talk to Jim I am sure they will look after you.
It's a good idea to change the break in fluid, drain into a clean pan and inspect for any chunks of metal in the fluid. It is normal to see small particles suspended in the fluid on the first oil change.
Personally I like Mobil 1 Synthetic , in our race cars it has shown good resistance to heat .
Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
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| Re: Final Drive Question [message #280658 is a reply to message #280655] |
Wed, 24 June 2015 16:32 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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I have about 2000 miles on my 3.70's and the whine is pretty well gone.
Then again, it never bothered me much as there are so many other noises
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: Final Drive Question [message #280739 is a reply to message #280658] |
Thu, 25 June 2015 22:13 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Keith V wrote on Wed, 24 June 2015 15:32I have about 2000 miles on my 3.70's and the whine is pretty well gone.
Then again, it never bothered me much as there are so many other noises
My GMC storage neighbor went through 3 units before he got a quiet one.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Final Drive Question [message #280766 is a reply to message #280739] |
Fri, 26 June 2015 08:54 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Jim had said they were having noise problems for a while. I think the current units are better.
Then again, I have pretty good tinnitus, so maybe I just can't hear it
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Final Drive Question [message #280787 is a reply to message #280766] |
Fri, 26 June 2015 13:06 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I have a set of 3:70 gears that I bought right after they were released.
Because I had a lot of time and not much money, plus I have set up many
differential gearsets including 10 bolt GM carriers, I thought "How hard
can it be ?" Well, it is harder than it looks. The carrier is moved left
and right by removing shims on one side of the case and adding them on the
other. The pinion, which is also the input shaft from the transmission,
comes out with the end plate, and is depth spaced with shims as well. No
crush sleeve is used, so, the depth has to be spot on before the carrier is
installed by spreading the housing. Not impossible, but time consuming. The
original gear sets lacked the precision polish that you might see on a set
of Richmond Gears, or original GM ones. I spent a lot of time setting mine
up, and got the gear tooth pattern right on with prussian blue. It should
have run quietly, but did not for the first 4 or 5 thousand miles until the
gears broke in to each other. I have seen some of the later gearsets, like
the ones now in production, and the polish on the gears is much finer, so
they should run quietly. I have about 20,000 miles on mine now. The lube
runs between 200 and 210 degrees at steady 65 to 70 mph. A bit more
climbing steep grades with long pulls. I am happy with that. Probably the
best performance upgrade that I have done to my coach. It will pull Manny's
hill with no issues.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Jun 26, 2015 at 6:54 AM, Keith V wrote:
> Jim had said they were having noise problems for a while. I think the
> current units are better.
> Then again, I have pretty good tinnitus, so maybe I just can't hear it
> --
> Keith Vasilakes
> Mounds View. MN
> 75 ex Royale GMC
> 69 Vette
> 29 Dodge
>
>
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> GMCnet mailing list
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