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Author Topic: V730 shimmy/shake  (Read 3027 times)
brando4905
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« on: March 09, 2011, 05:43:52 AM »

Hey Folks,

When I take off from a stop I get a shimmy or shake for a hundred feet of so, then all is well and no slipping or shimmy in any other gear. Taking off real slow helps, but still feel a shimmy. Could this be bad motor mounts or something other than the trans.? Fluid is at correct level and has new filter.

Thanks,
Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
mcidave
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« Reply #1 on: March 09, 2011, 06:19:40 AM »

I do not get the shimmy/shake with my trans...But I do get a real hard buck right at the end of the granny gear going into the second gear and after that all is smooth!
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luvrbus
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« Reply #2 on: March 09, 2011, 06:22:04 AM »

If a GM has a drive shaft out of time U joints will cause that
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mcidave
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« Reply #3 on: March 09, 2011, 06:24:57 AM »

It a MCI9 1982 model but will keep that in mind when I get the tranny services comming up.
Thanks
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brando4905
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« Reply #4 on: March 09, 2011, 06:29:01 AM »

Clifford,

Thanks for the reply, how do I tell if they are out of time? Bad motor mounts not an issue in this situation?
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
bevans6
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« Reply #5 on: March 09, 2011, 07:07:43 AM »

very easy visual inspection, normally the U=joint caps are in line with each other.  the  driveshaft can vibrate a bit or cause a bit of a surge if the caps are out of line, more so the greater the angle the joints are at.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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luvrbus
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« Reply #6 on: March 09, 2011, 07:24:06 AM »

Brandon, the drive line should have arrows to time the shaft align the arrows all there is to it


good luck
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brando4905
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« Reply #7 on: March 09, 2011, 07:25:55 AM »

Thanks guys, I'll let you know what I find out.
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
gus
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« Reply #8 on: March 09, 2011, 03:04:22 PM »

Your slip joint grooves may be worn out, happened to me with the same symptoms and also a clicking at very slow speed.
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Charley Davidson
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« Reply #9 on: March 09, 2011, 03:41:05 PM »

I would make sure your U joints are good, I broke a tranny in half on my 4905 cause the front U joint gave out & the drive shaft came loose at the differential and bound up in the bulkhead at 70 mph.
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brando4905
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« Reply #10 on: March 10, 2011, 04:00:09 AM »

Gus,

Gonna check all of this out today hopefully, really hoping it's something in the drive shaft.

Charley,

That does not sound good, I've heard similar horror stories about buffalo drive shafts doing serious damage.
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
robertglines1
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« Reply #11 on: March 10, 2011, 11:38:05 AM »

If it is not drive line connected--check pulley for looseness on engine as they will sometimes correct with rpm building. or the smart mouth part of me says   Don't start off on rumble strips!  wishing it is a simple fix. Happy bussing  Bob   please post findings
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
robertglines1
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« Reply #12 on: March 10, 2011, 11:39:52 AM »

Does it do it when trans warmed up?
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #13 on: March 11, 2011, 06:22:51 AM »

Brandon, go find Bill Gerrie over at BNO, he's pretty good with the V trannies.

happy coaching!
buswarrior
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brando4905
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« Reply #14 on: March 11, 2011, 08:39:09 AM »

Thanks guys for all the suggestions. Drive shaft and u-joints seem OK, but have found a pretty good size crack in the rear bulkhead. Angry Angry

My mechanic is going to plate the damaged area with 1/4" steel on both sides. Got a feeling this is where the shimmy is coming from.

I'll give an update when we figure it out.

Thanks,
Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
wildbob24
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« Reply #15 on: March 11, 2011, 09:24:45 AM »

Brandon,

A cracked bulkhead was pretty common on the early 4106s, not very common on our models. Is it around the area that was removed for the V730 install?

Bob
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P8M4905A-1308, 8V71 w/V730
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brando4905
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« Reply #16 on: March 11, 2011, 09:31:32 AM »

Bob,

Haven't seen it in person yet, but from David's description this is the area in question.

Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
RJ
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« Reply #17 on: March 11, 2011, 09:45:44 AM »

Brandon -

The cracked bulkhead is a common problem when installing a V-730 in a coach that didn't come with one from the factory.  Reinforcing it is the proper repair.  Suggest that the steel be treated with POR-15 before installation, to reduce rust issues.  Also, a sheet of plastic or similar to reduce the risk of galvanic corrosion between the steel plates and the aluminum bulkhead is a good idea, too.

The following little detail is often overlooked when folk install a V-730 into a coach that didn't have one as OEM:

OEM has a support bracket that runs from the bulkhead to the rear bumper cradle, with a donut-like rubber bushing.  This helps spread the weight load of the transmission, so that it's not all hanging off the engine's bell housing.

I'll see if I can find a photo, but in the meantime, you might try calling Luke to see if he's got the necessary parts in his collection.  888-262-2434 will get you thru to him.

Might also suggest replacing the motor mounts on the bulkhead while you're in there.  Chances are that the additional movement due to the cracked bulkhead has accelerated their wear.

FWIW & HTH. . .

 Wink

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RJ Long
PD4106-2784 No More
S13406 Now
Fresno CA
brando4905
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« Reply #18 on: March 11, 2011, 11:23:12 AM »

RJ,

Thanks for all the good advice. A photo would be great if you can dig one up.

I think that I have the OEM support bracket, it goes from the bulkhead to bumper under the trans. and has a mini airbag on top that the trans. sits on.

Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
RJ
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« Reply #19 on: March 11, 2011, 05:57:57 PM »

Brandon -

That's exactly what I was talking about - the bracket with a mini-airbag-like bushing to support the transmission.

Send me the actual VIN on your coach.  Besides the normal delivery roster that I have which tells who originally bought the coach from GMC, I've got another, very, very rare roster that lists the Buffaloes that had V-730s OEM.  You might have one of these rare Buffs!

The plot thickens!

 Wink
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RJ Long
PD4106-2784 No More
S13406 Now
Fresno CA
brando4905
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« Reply #20 on: March 12, 2011, 04:15:40 AM »

RJ,

It's H8H-649  A155, it has a clutch pedal, so not an OEM installation. Not sure who did the swap, pretty sure it was after Anderson took it out of service.

Thanks,
Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
brando4905
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« Reply #21 on: March 18, 2011, 12:02:26 PM »

Little bit of an update,

Gus, slip joint splines do have some wear. Having a new shaft made.

So, once we get the bulkhead repaired and put in the new drive shaft, I'm hoping the shimmy at take off will be gone.

Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
gus
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« Reply #22 on: March 19, 2011, 06:53:23 PM »

Brandon,

Let us know the final outcome.
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brando4905
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« Reply #23 on: March 22, 2011, 12:19:59 PM »

New driveshaft and repaired bulkhead=no more shimmy/shake!  Grin

Thanks for all the help guys.

Gus, thanks for pointing me in the right direction.
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1980 GMC H8H-649  8V71/V730 Marion,NC

"The highway is for gamblers, better use your sense" -Dylan
wildbob24
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« Reply #24 on: March 22, 2011, 12:22:01 PM »

Brandon,

Excellent news. Glad the fix was relatively minor.

Bob
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P8M4905A-1308, 8V71 w/V730
Custom Coach Conversion
Duluth, GA
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