| Re: [GMCnet] Final Drive Options and Recommendations [message #220371 is a reply to message #220331] |
Thu, 29 August 2013 16:56   |
powerjon
Messages: 2446
Registered: January 2004
Karma:
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Senior Member |
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I am with the rest on recommending the 3.55 gear as a minimum upgrade. The 3.07 gear is too high a ratio for the coach. I had a lower 3.55 in our 403 77 Eleganza II and it really woke up the motor, got it up on the powerband. We run a 3.66 ratio in the stretch by using a 3.21 final and a 3.50 chain in the transmission. With the 3.07 the motor never gets up on the cam and is always lugging and you re constantly downshifting even here in the Midwest. Jim K stocks the gear right here in the Midwest in Marysville, OH., so you will have it in a few days. You can't go wrong, it will change your coach for the best.
JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan
On Aug 29, 2013, at 1:12 PM, Mickey Szilagyi <mickey@apex-internet.com> wrote:
>
>
> Our 77 Kingley is in the shop and we've found that the final drive has a bad gear. Sorry, I don't know the specific name of the gear but our problem is that there is a lot of slack when the coach is first put in drive. The gears move a lot before it actually engages. I think we have a bad/cracked ring. Whether the pinion is OK is still being determined. We have a 403 and we believe the 3.07 OEM final drive. We're now trying to decide whether to fix the current unit or replace or upgrade it to a different ratio unit. We've read a bunch of info on the forum but still have a few questions.
>
> 1. On Gene's chart it shows a Toro 2.73 FD and then the Original 3.07. Does that mean the 3.07 was specifically developed for the GMC coaches or is the 3.07 a carry over from the Toros?
>
> 2. We have a 403, live in Michigan but plan to travel with the coach all over the country so the terrain will vary. We will probably stay in MI or the Great Lakes region however most of the time.
>
> 3. We may also wish to tow a small utility trailer, small boat but also a small vehicle.
>
> With the above in mind is repairing the 3.07 OK or should we change to another FD ratio?
>
> We have American Eagle aluminum wheels with Michelin 225/75R16E1 tires.
>
> We see Cinnabar has the 3.42 FD and JimK has 3.55 and 3.70 FDs.
>
> We realize we will get a variety of responses and opinions on this and that there isn't the perfect solution but we appreciate all you help as we have in the past.
>
> Thanks!
>
>
> --
> Mickey
> 1977 Kingsley, 403, Lansing, MI
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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