GMC 3.42 final drive and Monteagle Mountain

[philip l. stewart]

Bill---

You asked whether my 455 is running OK since crossing Monteagle Mt. (TN)
on I-24 causes speed on by 76 coach to drop off when hitting the grade
at 60 mph.

Good question and I thought the engine was running fine until you
mentioned that your 23 footer cruises right over the top without a loss
of speed.

This may be like the other question I can't answer which is why I don't
record those 10 mpg averages that others report on their coaches (9.5 is
the best I ever recoreded and I only average 7.5).

This just points out the value of this GMCnet. It's a great place to
get a frame of reference for how things stack up in view of the
experiences of many owners of the GMC. Hopefully, the information
shared will help folks make an informed decsion on where improvements
are really possible and pactible with these 20 + year old machines.

Thanks for your comment.

Phil Stewart

 

[william d. minor]

Phil,

I lose a couple of mph, but the truckers called me a 'Hot-Rod Motorhome'
when I passed them. My mpg average is between 10 and 10.5, with a best
of 13.3 (when not exceeding 50 while escorting a friend's wounded SOB),
and a worst of 6 while fighting a 40 mph headwind and using
re-formulated gas. My brother has a '76 Palm Beach, and he averages
about 8 mpg, but he runs 70+ almost all the time. I have a vibration
(maybe a bent shaft) and I don't like to go that fast most of the
time. I generally cruise at about 60 -62 mph as the coach seems to be
smoothest there As long as the speed stays above 55, I have no problems
staying on cruise up any hill I found so far. I am running a K&N air
filter as well as a 4" cold air hose to the air cleaner, but I still
have standard mufflers and 2 1/2" exhaust pipe. When I first got the
coach, I lost a lot of speed on long hills, but not since the air intake
improvements as well as a complete tuneup.

Hope this helps,

Bill