3.55:1 Final Drive

[chuck blanford]

Darren

The jury's still out on the 3.55, as it's yet untested for the intended
application. I have a 403, and towing a 3,600 pound Wrangler over the
passes with the 3.07 gears was a "challenge". We actually started
disconnecting and driving the Jeep over the passes. Very inconvenient. On
the trip from north Idaho to southwest Oregon, we towed the 2,400 pound
Tracker, and it's almost non-existent back there. This was our first trip
with the Tracker in tow, and I was very pleased with the 403/3.07
performance. On the return trip with the 3.55, I felt like I had lost more
on the upper end than I had gained on the lower end. Cockpit noise was
definitely increased, and I kept looking at the shift indicator to make sure
I wasn't in 2nd. Dropping to 2nd for engine braking on the downhill grades
really gets things wound up (read "noisy"). I don't have a tach, so can't
give specifics. And don't ask about mpg; for the 1K to 2K miles per year,
fuel cost is an inconsequential component in the overall annual cost of
ownership, and I don't calculate mpg. Being "cubicle-captive", we enjoy the
limited travel opportunities, and 8 or 11 mpg is not going to be the
decision criteria.

The intended application is towing the Jeep, and we've yet to do that. I've
got to finish a transfer case tail-shaft conversion, but that's another
story. I'll let you know if there's substantial improvement once I have an
opportunity to tow the Jeep again.

Other than the labor $, this was a low risk conversion for me, as I have a
3.07 final drive attached to the new 403 engine and transmission I purchased
a couple years ago.

Chuck

> Date: Sat, 10 Jun 2000 21:41:46 -0600
> From: Darren Paget
> Subject: Re: GMC: Gary Miller e-mail address
>
> Hey Chuck. How do you like the 3:55? I am still having opinions
> on whether or
> not to go 3:55 or 3:70. Darren
>

>
> > Try this for Gary - I communicated with him in April before I headed to
> > North Bend, OR for the 3.55:1 final drive install.
> >
> > Gary Miller [gmcmotorhome]
> >
> > Sorry for the delay, or if this has already been posted - I'm
> "digesting"
> > these days.
> >
> > Chuck
> > 77 Kingsley
> > North ID
>

 

[emerystora]

>Darren
>
>The jury's still out on the 3.55, as it's yet untested for the intended
>application. I have a 403, and towing a 3,600 pound Wrangler over the
>passes with the 3.07 gears was a "challenge". We actually started
>disconnecting and driving the Jeep over the passes. Very inconvenient. On
>the trip from north Idaho to southwest Oregon, we towed the 2,400 pound
>Tracker, and it's almost non-existent back there. This was our first trip
>with the Tracker in tow, and I was very pleased with the 403/3.07
>performance. On the return trip with the 3.55, I felt like I had lost more
>on the upper end than I had gained on the lower end. Cockpit noise was
>definitely increased, and I kept looking at the shift indicator to make sure
>I wasn't in 2nd. Dropping to 2nd for engine braking on the downhill grades
>really gets things wound up (read "noisy"). I don't have a tach, so can't
>give specifics. And don't ask about mpg; for the 1K to 2K miles per year,
>fuel cost is an inconsequential component in the overall annual cost of
>ownership, and I don't calculate mpg.
>
> Chuck Blanford

I also have the 3.55 which I put in last fall. I also tow a Jeep.
it is a 1978 CJ7 (the last of the V-8s). i believe that it is even
heavier than the Wrangler. We have found the 3.55 to give much
better performance on the hills and better acceleration on the flats.
I had the same impression when I first got it. I kept waiting for
the transmission to shift into high gear and a couple of times even
manually downshifted to second to make sure that it was in high gear.
It definitely is more noisy. I put in one of Darren's insulating
blankets (1/2") and it does a good job in keeping down the noise in
the cockpit as well as the heat.

I have much better performance on the mountain roads in my area and
probably better gas mileage on hills but on my trip to Florida and
Rayne, LA. in Feb. & March on relatively level roads, my gas mileage
actually went down from what it had been with the 3.07 transmission
on previous trips over the same route.

Automobile manufacturers have, over the years, came up with higher
gear ratios (lower numberically) that are actually an "overdrive".
They have done this to improve gas mileage. As some of you know, I
had a 2.73 final drive in for a while that a transmission shop in Las
Vegas, NV (Best Auto - don't ever go there as they have totally
screwed me and stone walled me on any compensation for the $1350 they
charged me for the wrong final drive!!!). I actually got better gas
mileage on the level road with the 2.73 than I was getting with the
3.07 but my performance on hills was terrible. Too bad GM didn't
have an overdrive feature available in the 425 GMC motorhome
transmission.

If any of you are planning to go with a lower gear ratio, do it for
the other benefits -- don't do it with the idea that you'll get
better mileage.

As an elderly motorhome salesman (probably about my age now) once
told me when I was looking for my first motorhome back about 1970 and
inquired about the gas mileage: "Son, if you've got to worry about
the gas mileage you shouldn't buy a motorhome -- you can't afford it."

Emery Stora
77 Kingsley
Santa Fe, NM

 

[ronald b. kazi]

Chuck-

What year is your Tracker? I am about to get a 2000.

Ron and Julie

> Darren
>
> The jury's still out on the 3.55, as it's yet untested for the intended
> application. I have a 403, and towing a 3,600 pound Wrangler over the
> passes with the 3.07 gears was a "challenge". We actually started
> disconnecting and driving the Jeep over the passes. Very inconvenient. On
> the trip from north Idaho to southwest Oregon, we towed the 2,400 pound
> Tracker, and it's almost non-existent back there. This was our first trip
> with the Tracker in tow, and I was very pleased with the 403/3.07
> performance. On the return trip with the 3.55, I felt like I had lost more
> on the upper end than I had gained on the lower end. Cockpit noise was
> definitely increased, and I kept looking at the shift indicator to make sure
> I wasn't in 2nd. Dropping to 2nd for engine braking on the downhill grades
> really gets things wound up (read "noisy"). I don't have a tach, so can't
> give specifics. And don't ask about mpg; for the 1K to 2K miles per year,
> fuel cost is an inconsequential component in the overall annual cost of
> ownership, and I don't calculate mpg. Being "cubicle-captive", we enjoy the
> limited travel opportunities, and 8 or 11 mpg is not going to be the
> decision criteria.
>
> The intended application is towing the Jeep, and we've yet to do that. I've
> got to finish a transfer case tail-shaft conversion, but that's another
> story. I'll let you know if there's substantial improvement once I have an
> opportunity to tow the Jeep again.
>
> Other than the labor $, this was a low risk conversion for me, as I have a
> 3.07 final drive attached to the new 403 engine and transmission I purchased
> a couple years ago.
>
> Chuck
>
> > Date: Sat, 10 Jun 2000 21:41:46 -0600
> > From: Darren Paget
> > Subject: Re: GMC: Gary Miller e-mail address
> >
> > Hey Chuck. How do you like the 3:55? I am still having opinions
> > on whether or
> > not to go 3:55 or 3:70. Darren
> >

> >
> > > Try this for Gary - I communicated with him in April before I headed to
> > > North Bend, OR for the 3.55:1 final drive install.
> > >
> > > Gary Miller [gmcmotorhome]
> > >
> > > Sorry for the delay, or if this has already been posted - I'm
> > "digesting"
> > > these days.
> > >
> > > Chuck
> > > 77 Kingsley
> > > North ID
> >