final drive thread

T

thomas g. warner

New member
Mar 24, 1998
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I would reason that if you are going to tow in florida where it is for the
most part flat, the 3.07 would be OK. If you decide on just replacing the
3.07 bearings and seals it will cost $219 from Gateway. If you decided to
go the 3.42 route buy the final drive with the gears already installed
unless you have confidence in your garage doing it and they have the proper
spreading tool and the spacers to set up the clearances right.

> With 95000 miles and bit of noise from my final drive its time to repair=
or
>replace.=20
>I would like to get the current thoughts and opinions on gear ratios,=
noise,
>longevity, price, labor involved, etc.
> My coach is 26' 1977, stock 455 and tranny, running 8.75 Bridgestones on
>steel wheels.
> As I frequently tow a 27' trimaran sailboat weighing about 4000 lb.. I=
feel
>that the 3.42 ratio may be about right.
> Nelson 77 Elle II 75=B0 and sunny in Orlando
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
If you drain the lubricant out and remove the cover, you'll probably be able
to find debris in the bottom of the carrier that will give you a clue as to
the nature of the problem. My guess is that it's probably bearing related.

Paul Bartz

From: F25CCapt [mailto:F25CCapt]
Sent: Wednesday, January 13, 1999 10:30 PM
Subject: Re: GMC: final drive thread

Thanks for the information on the bearings and seals. Without disassembly
is it possible to determine if the noise is bearing or gears? You're right
that towing in Florida is not to bad with the 3.07, however we have taken
this rig to Lake Erie last year and plan on more trips through the mountains
in the future. If I decide to go with 3.42 where would the best place to get
them, and any idea of the cost? As I plan on doing the swap myself I need
the bolt on assembly.
 
If the final drive is making noise, chances are there would be metal if you
drained the fluid or took the pan off to take a look. That noise would
have to be metal-metal contact which is sure to put some metal in the oil.
I guess you could probably even get the oil analyzed to find out exactly
which parts are failing just like many do with their engine oil.

The 3.42 is only available from Cinnabar I think. All the others have
slightly different ratios. I will again say that we don't think the 3.42
did much for us at all and hurt the gas mileage a little. I know others
really like them though, so YMMV. Whichever one you get, I would suggest
trying to get one that is already assembled because there are some special
tools needed to do the job 100% correct. That said, we did rebuild our
3.07 ourselves (just changing all the bearings after a total bearing
failure). It went for another 15,000 miles or so just fine before we
swapped it out for the 3.42. Therefore, putting it back together 100%
correct may not be all that important.

Zak

PS - I love the stories of people that are "hoping" for a failure so they
can spend $1500 :). I think I'd rather hope that the $1500 could stay in
my pocket. IMHO, $1500 could be much better spent on the engine to get
enough power to stay with the 3.07 or even go to the 2.73.

>Thanks for the information on the bearings and seals. Without disassembly is
>it possible to determine if the noise is bearing or gears? You're right that
>towing in Florida is not to bad with the 3.07, however we have taken this rig
>to Lake Erie last year and plan on more trips through the mountains in the
>future. If I decide to go with 3.42 where would the best place to get them,
>and any idea of the cost? As I plan on doing the swap myself I need the bolt
>on assembly.
>
 
> Thanks for the information on the bearings and seals. Without disassembly is
> it possible to determine if the noise is bearing or gears? You're right that
> towing in Florida is not to bad with the 3.07, however we have taken this rig
> to Lake Erie last year and plan on more trips through the mountains in the
> future. If I decide to go with 3.42 where would the best place to get them,
> and any idea of the cost? As I plan on doing the swap myself I need the bolt
> on assembly.

Cinnabar sells the 3.42 for $1195 exchange. The speedo adapter adds $75. They
will install the complete outfit for $1511.26 (incl parts, labor & tax).

Clark
78 Kingsley
Mt. Pleasant, MI
 
Speaking of Cinnabar.....
(A) do they have their own web site?
and if they do....
(B) what is the address?

Terry
'75 GMC Avion
 
Terry:

Apparently not so far. However, Wes Coughlin, the owner, can be contacted
via e-mail: gmcmh .

Paul Bartz

From: LA-HOGS [mailto:LA-HOGS]
Sent: Thursday, January 14, 1999 11:24 PM
Subject: Re: GMC: final drive thread



Speaking of Cinnabar.....
(A) do they have their own web site?
and if they do....
(B) what is the address?

Terry
 
Clark:

That's not the total story for the exchange (i. e. $1195). Unless you pick
up the gears from Cinnabar in Sandusky MI, there are freight charges
involved both ways in the deal, plus some hardware to reassemble the axle
half-shafts, seal(s), and gear lube is involved.

I believe for the money and aggravation involved doing it alone, a trip to
have Cinnabar do the change is well worth it. IIRC, it works out to
approximately $100 difference, which is for their labor.

Paul

From: searlecj [mailto:searlecj]
Sent: Thursday, January 14, 1999 9:49 PM
Subject: Re: GMC: final drive thread

Thanks for the information on the bearings and seals. Without disassembly
is it possible to determine if the noise is bearing or gears? You're right
that towing in Florida is not to bad with the 3.07, however we have taken
this rig to Lake Erie last year and plan on more trips through the mountains
in the future. If I decide to go with 3.42 where would the best place to get
them, and any idea of the cost? As I plan on doing the swap myself I need
the bolt on assembly.

Cinnabar sells the 3.42 for $1195 exchange. The speedo adapter adds $75.
They will install the complete outfit for $1511.26 (incl parts, labor &
tax).

Clark
78 Kingsley
Mt. Pleasant, MI
 
Buskirks sells the 3.55 final for about 1490.00 installed with speedo
gear and installation. About 1200 for just the final drive and speedo
gear alone.

>
>
>
> Speaking of Cinnabar.....
> (A) do they have their own web site?
> and if they do....
> (B) what is the address?
>
> Terry
> '75 GMC Avion
 
>
>
> Speaking of Cinnabar.....
> (A) do they have their own web site?
> and if they do....
> (B) what is the address?
>
> Terry
> '75 GMC Avion

Believe the address is gmcmh
 
If you are in Orlando than either have Jim bounds, Alex Sirum or Golbys do=
it.

>Paul, thanks for the suggestion on having cinnabar do the final drive swap.=
If
>the weather in Sandusky was better and it was about a thousand miles closer=
to
>Orlando I'd have them do it.
>Nelson 77 Eleganza 75=B0 and sunny in Orlando
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
Do I detect that you think there is something wrong with the weather =
here in
Michigan????? Kalamazoo was sunny and 41 deg F today. Sled dog races =
are
going on this weekend.

Paul Bartz

- -----Original Message-----
From: F25CCapt
To: gmcmotorhome
Sent: 1/15/99 9:21 PM
Subject: Re: GMC: RE: final drive thread

Paul, thanks for the suggestion on having cinnabar do the final drive
swap. If
the weather in Sandusky was better and it was about a thousand miles
closer to
Orlando I'd have them do it.
Nelson 77 Eleganza 75=B0 and sunny in Orlando
 
I have only been reading about the 3.42 vs 3.07 for the last couple of days
here in this publication, and I haven't seen one mention of the difference
in fuel consumption. It shouldn't take a genius or rocket scientist long to
figure there is going to be a change. My question is how much of a
change???? I couldn't be convinced to change mine over to the 3.42:1 and
there also is a 3.57:1, I believe available. I have a rig that was changed
from the 403 Turbo to a 455 by the original owner. I also drive in the
mountains quite a bit and tow either a Toyota pickup or 19 foot boat. It has
more power than one needs, of course it has headers, a 3.5" exhaust system
and recently added a transmission cooler that sits in the wheel well and has
its own thermostatically operated fan to lower heat transfer to the engine.
My mileage runs on the average about 10+ miles per gallon pulling boat or
truck, and about 12+ without the tows.
My traveling sidekicks get about the same with their SOB's, but they don't
tow anything. They lose 5 to 10 miles per hour climbing hills with the
autopilot engaged and so do I, but that is the fault of the autopilot not
doing a good job.
That enough food for thought.

srchrls
78 Birchaven
 
Nice pictures... looks like quite a project. Keep us informed
Al Chernoff
77 Eleganza II

>
> >http://members.aol.com/gmcgrlk/index.htm t=_self]Home Page[/url]
>
> Scott
>
> I have to commend you on your newest www page. Your really comin along!
>
> I was able to access it with Netscape 4.5 and it all looks real good. I
> really appreciate gettin to look at places like you depict without having
> to tear into my own coach. It's really helpful!
>
> bdub
> '76 Palm Beach
> In The Heart o Texas
> www.web-access.net/~bmassey/
> icq # 202333
 
Do these larger exhaust sizes really fit well? We have a 3" (stock is
2.5") and it just fits through the original exhaust silicon rings. Any
larger would definitely require removing those mounts and some other mods I
would think. I can't see bigger than 3" being much of an improvement.
Does anyone here have experience with larger than 3"? We will probably be
redoing our exhaust in stainless soon, so we are interested in any new info
on this topic. By the way, does anyone here have any experience with the
stainless exhaust advertised in the GMCMI newsletter classifieds? We were
considering getting that system (with the 3" upgrade), but if we can't find
anybody that has experience with it, we will probably just fabricate our own.

Zak

>I know alot of people have been using 4" exhaust pipes--is there some
reason for
>using the 3.5 in.?
>Scott Adohen
>
 
I haven't heard of anyone using a 4" exhaust, you can't get it down thru
the frame rails unless you cut the frame cross members and I wouldn't
recommend that, and you sure don't want it hanging down underneath the
frame. The 3" exhaust is the largest that will fit right down the frame
rail holes without any problems. Any thing larger than a 3" system and
Hi-flow type mufflers is money not spent well. I myself have a 403 with
2.5" flowmaster into the stock 2.5" exhaust tail pipe. When I got rid
of the stock 2" mufflers the larger piping and higher flow mufflers (220
cfm each compared with 110 cfm stock) my fuel mileage went up from 8.9
to 10.8 mpg. (I run 67-68 mph on most X-ways with the cab air on).
Would probably be even better if I ran more towards 62 to 64 mph. The
403 is approx. 20% smaller in displacement than the 455 and the 3" is
marginal change. The 455 really likes the 3" tail pipe and larger
mufflers. Header are an options that you need to decide if you really
need them. I keep after my maintenance on the motor and do not have
exhaust manifold leaking problems. I use a Fel Pro #1439 gasket along
with the high temp copper silicone. I also use grade 8 cap screws type
bolts with liberal amount of high temp nickel never seize. I use a
torque to tighten the bolts (25 ft/# and do a quick check of them every
4 to 5 thousand miles. I just installed a 3.55 final drive this fall
and do not have enough data to determine how much if any the fuel
mileage will drop. The new gearing gets the motor up into its power
band and doesn't lug anymore (should burn the fuel better). Used to
slow down 10 to 15 mph on some hills with the 3.07 gear, but with this
3.55 the mph did not drop off at all. The cruise kept it right at 64
mph. Better quit, getting too wordy.

J.R.Wright
GMC Greatlaker
77 Eleganza II
Michigan

>
> Do these larger exhaust sizes really fit well? We have a 3" (stock is
> 2.5") and it just fits through the original exhaust silicon rings. Any
> larger would definitely require removing those mounts and some other mods I
> would think. I can't see bigger than 3" being much of an improvement.
> Does anyone here have experience with larger than 3"? We will probably be
> redoing our exhaust in stainless soon, so we are interested in any new info
> on this topic. By the way, does anyone here have any experience with the
> stainless exhaust advertised in the GMCMI newsletter classifieds? We were
> considering getting that system (with the 3" upgrade), but if we can't find
> anybody that has experience with it, we will probably just fabricate our own.
>
> Zak
>

>
> >I know alot of people have been using 4" exhaust pipes--is there some
> reason for
> >using the 3.5 in.?
> >Scott Adohen
> >
 
>http://members.aol.com/gmcgrlk/index.htm t=_self]Home Page[/url]

Scott

I have to commend you on your newest www page. Your really comin along!

I was able to access it with Netscape 4.5 and it all looks real good. I
really appreciate gettin to look at places like you depict without having
to tear into my own coach. It's really helpful!

bdub
'76 Palm Beach
In The Heart o Texas
www.web-access.net/~bmassey/
icq # 202333
 
I changed to the 3.42:1 ring and pinion gear in Aug 1996 in my 78 Royale
with a 403. I notice no difference in mileage.

As to the autopilot (cruise control) not doing its job I don't agree. As I
said in response to e-mail a week or so ago, I've proven that the 403 with
the 3:42 to 1 gearing and 3" exhaust can outperform a stock 455 with
original ring and pinion gears on hills.

Paul Bartz

From: srchrls [mailto:srchrls]
Sent: Monday, January 18, 1999 12:02 AM
Subject: GMC: Final drive thread

I have only been reading about the 3.42 vs 3.07 for the last couple of days
here in this publication, and I haven't seen one mention of the difference
in fuel consumption. It shouldn't take a genius or rocket scientist long to
figure there is going to be a change. My question is how much of a
change???? I couldn't be convinced to change mine over to the 3.42:1 and
there also is a 3.57:1, I believe available. I have a rig that was changed
from the 403 Turbo to a 455 by the original owner. I also drive in the
mountains quite a bit and tow either a Toyota pickup or 19 foot boat. It has
more power than one needs, of course it has headers, a 3.5" exhaust system
and recently added a transmission cooler that sits in the wheel well and has
its own thermostatically operated fan to lower heat transfer to the engine.

My mileage runs on the average about 10+ miles per gallon pulling boat or
truck, and about 12+ without the tows.

My traveling sidekicks get about the same with their SOB's, but they don't
tow anything. They lose 5 to 10 miles per hour climbing hills with the
autopilot engaged and so do I, but that is the fault of the autopilot not
doing a good job.
 
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