Final Drive - which to pick?

[john wright]

You can get the 3.55 all set up from Buskirks. I have had a 3.55 final
since Oct. of last year and have 6000 miles with no noise or problems.
Made a big difference in the mountains and hills and when towing.

J.R. Wright
GMC GreatLaker
77 Eleganza II
Michigan

>
> I am ready to order a lower ratio final drive. The questions is which one to
> put in. Cinnabar has a 3.42, Applied Air Filters and Gearmaster (Marvin
> Peck) are advertising in Motorhome Marketplace drives that are 3.55 and 3.67.
>
> I lean toward the 3.42 only because I think that its 11.4% increase should be
> more than adequate based on my use of the 3.07 the last 18 years. Also, I
> feel it very likely that Cinnabar will be around for a long time.
>
> I don't know anything about Applied Air Filters and their gears.
>
> I have had no experience with Gearmaster but it would be a much lower gear
> ratio. About a 20% increase.
>
> Using the info that some posted about RPM at 60 mph being approx. 2300 rpm,
> this would give the following for the ratios 3.07, 3.42 and 3.67: 2300,
> 2562 and 2750. At 70 mph the rpms would go to 2683, 2989 and 3208.
>
> Since I do much of my driving toward the 70 mph on highways I think that the
> 3.67 might be a bit too much.
>
> Does anyone have a plot of the power/torque curves? I believe someone said
> that it is about 2800 rpm where they both peak.
>
> I don't want to analyze this to death but I have to live with my choice.
>
> BTW while searching the net I came across a large transmission/differential
> distributor that carries several of the major lines. They specialize in
> rebuilding and supplying gears for differentials. I called and talked to
> someone there who said he was familiar with the 3.42 setup and said that
> these higher ratios were not GM parts but were privately developed by others.
> He said the 3.42 was only available from someone in Michigan [ Cinnabar,
> obviously]. He also said that there apparently was someone in Texas that had
> an even higher gear [ must be Marvin Peck].
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[bartz paul]

Emery:

Time hasn't permitted me mentioning this yet, but earlier this week, because
Scott said he had a local shop looking into finding out what ring and pinion
gear sets might be available from other than the traditional sources (i. e.
Cinnabar, etc.), I decided to look in JEG's catalog and found they have a
section on Richmond gears. So I called them and asked what they had for
mid-70s Toronado's. They told me that they did not have any catalog
application listing anything for Toro's. I then got Richmond's number,
864-843-9231. They answer as Ohio and Richmond Gear and are located in
South Carolina. I talked there to Dean.

I found him apparently very knowledgeable on ring and pinion gears. My
question to him was similar to what I asked JEG's. He said they had none.
He said that the reason other gear sets won't work is the stubbiness of the
Toro pinion gear.

Dean was knowledgeable of the 3.42 gear set and said that they produce them
for Cinnabar who bought/paid for the molds.. In fact he said Cinnabar has
an order in to them for an additional 200 sets.

As to a torque curve, I have one in the house, but have apparently misplaced
it for the time being. I've been looking for it for a month for other
reasons. Chuck Stoddard sent it to me a number of years back. The top of
the torque curve is ~ 2800 rpm. Once I locate it I can make a copy of it,
although it isn't good quality to start with.

Looking at your numbers below, with 3.42 ratio, at 60 mph, my tach indicates
~2450 rpm.

Didn't the 3.55 ratio result from the noise problems Marvin Peck had with
the 3.46 ratio and was an attempt to get that monkey off his back??

Paul Bartz

From: EMERYSTORA [mailto:EMERYSTORA]
Sent: Friday, September 03, 1999 4:14 PM

I am ready to order a lower ratio final drive. The questions is which one
to
put in. Cinnabar has a 3.42, Applied Air Filters and Gearmaster (Marvin
Peck) are advertising in Motorhome Marketplace drives that are 3.55 and
3.67.

I lean toward the 3.42 only because I think that its 11.4% increase should
be
more than adequate based on my use of the 3.07 the last 18 years. Also, I
feel it very likely that Cinnabar will be around for a long time.

I don't know anything about Applied Air Filters and their gears.

I have had no experience with Gearmaster but it would be a much lower gear
ratio. About a 20% increase.

Using the info that some posted about RPM at 60 mph being approx. 2300 rpm,
this would give the following for the ratios 3.07, 3.42 and 3.67: 2300,
2562 and 2750. At 70 mph the rpms would go to 2683, 2989 and 3208.

Since I do much of my driving toward the 70 mph on highways I think that the

3.67 might be a bit too much.

Does anyone have a plot of the power/torque curves? I believe someone said
that it is about 2800 rpm where they both peak.

I don't want to analyze this to death but I have to live with my choice.

BTW while searching the net I came across a large transmission/differential
distributor that carries several of the major lines. They specialize in
rebuilding and supplying gears for differentials. I called and talked to
someone there who said he was familiar with the 3.42 setup and said that
these higher ratios were not GM parts but were privately developed by
others.
He said the 3.42 was only available from someone in Michigan [ Cinnabar,
obviously]. He also said that there apparently was someone in Texas that
had
an even higher gear [ must be Marvin Peck].

 

[john wright]

Emery,
It was $1150 for the set up drive with exchange, $65 for the speedo
gearbox and 3 hours labor @$52 an hour.

J.R.Wright

>

>
> since Oct. of last year and have 6000 miles with no noise or problems.
> Made a big difference in the mountains and hills and when towing.
>
> J.R. Wright >>
>
> JR - what did you pay for the product and also for the installation.
> Separately, if you have the breakdown.
>
> Thanks
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[john wright]

Emery,
As an old DOW guy your more than welcome!

John

>

>
> It was $1150 for the set up drive with exchange, $65 for the speedo
> gearbox and 3 hours labor @$52 an hour.
>
> J.R.Wright >>
>
> John -- Thanks for your help. I ordered a 3.55 unit from Applied Air filters
> (it seems that they also sell to Buskirk). Their ad in GMCMM showed a line
> that indicated they had special pricing for dealers. I called them and told
> them it was for my own motorhome but I had a NM reseller's tax number and a
> Fed ID business number. I also told them I might have some others who want
> one. They sold me the unit for $1,050 plus freight. This included the
> speedometer gearbox. The unit has new bearings and new seals and came with
> both the cover and transmission gaskets. They charged me $50 outbound
> freight and UPS charged me $57 to send the core back.
>
> Since I'm now a dealer, if anyone you know wants one at my cost have them
> contact me.
>
> I installed the new unit on Wed. and took it for a 20 mile test drive up as
> many hills as I could find in the direction I drove. Definitely more peppy.
> I noticed right away the higher rpm in the sound of the engine. At highway
> speeds I kept thinking that I had it in second gear. I guess I'll get used
> to that. I haven't tried it with a toad yet but I expect that it'll make
> quite a difference in my hill climbing ability. It certainly did on my test
> drive.
>
> Again, thanks for your input that helped me to make my decision.
>
> Emery