Final Drive Ratio
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What type of an air fuel gauge did you put in??
gene
>Arch,
>
> Here is some more info on lower final drive ratios. Two years ago I
>installed the equilivant of a 3.70:1 final drive and still have 8.75 x 16=
=BD"
>tires. Cruising, the engine turns 2800 rpm at 60 mph. My torque converter
>has slightly less slippage than stock. I have headers and 3" exhaust and
>went from .072 to .074 primary jets. I just put a air/fuel mixture gauge in
>this winter, so I'll see if it's too lean or not. The tail pipe indicates a
>slight rich condition most of the time though. I use an MSD knock sensor
>and ignition timing adjuster. I can easily run at 12=B0 and sometimes 14=B0
>advance. Engine temperature hasn't changed but transmission temperatures=
are
>a bit lower. Gas mileage varies a quite a bit from fill to fill. The yearly
>average has changed very little and usually comes in at slightly above or
>below 9 mpg.
>
> With the engine running 20% faster at any given speed, the noise was=
too
>high so the fan pulley on the engine was changed from the stock of 8" in
>diameter to 6=BD ". Everything works fine including no change in engine
>temperature.
>
> There is a great change in performance and driving. The coach will
>cruise up and down hill with ease ( and stays in high gear most of the=
time)
>as will as into and out of corners. Of all the changes I've made to the
>coach, changing the final drive ratio has been the best.
>
>
> Al Hamilton
> 76 Eleganza II
> Kingston, Ont
>
> Patrick,
>
> Thanks for the Bridgestone website.
>
> Al
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
gene
>Arch,
>
> Here is some more info on lower final drive ratios. Two years ago I
>installed the equilivant of a 3.70:1 final drive and still have 8.75 x 16=
=BD"
>tires. Cruising, the engine turns 2800 rpm at 60 mph. My torque converter
>has slightly less slippage than stock. I have headers and 3" exhaust and
>went from .072 to .074 primary jets. I just put a air/fuel mixture gauge in
>this winter, so I'll see if it's too lean or not. The tail pipe indicates a
>slight rich condition most of the time though. I use an MSD knock sensor
>and ignition timing adjuster. I can easily run at 12=B0 and sometimes 14=B0
>advance. Engine temperature hasn't changed but transmission temperatures=
are
>a bit lower. Gas mileage varies a quite a bit from fill to fill. The yearly
>average has changed very little and usually comes in at slightly above or
>below 9 mpg.
>
> With the engine running 20% faster at any given speed, the noise was=
too
>high so the fan pulley on the engine was changed from the stock of 8" in
>diameter to 6=BD ". Everything works fine including no change in engine
>temperature.
>
> There is a great change in performance and driving. The coach will
>cruise up and down hill with ease ( and stays in high gear most of the=
time)
>as will as into and out of corners. Of all the changes I've made to the
>coach, changing the final drive ratio has been the best.
>
>
> Al Hamilton
> 76 Eleganza II
> Kingston, Ont
>
> Patrick,
>
> Thanks for the Bridgestone website.
>
> Al
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
Emery,
The 3.70:1 ratio came from changing both gears or sprockets at the rear
of the transmission and using the original chain and 3.07 final drive.
Al Hamilton
76 Eleganza II
Kingston, Ont
The 3.70:1 ratio came from changing both gears or sprockets at the rear
of the transmission and using the original chain and 3.07 final drive.
Al Hamilton
76 Eleganza II
Kingston, Ont
Al:
Where did you get your gears??
Paul Bartz
From: Al Hamilton
Sent: 1/15/00 10:25 AM
Emery,
The 3.70:1 ratio came from changing both gears or sprockets at the
rear
of the transmission and using the original chain and 3.07 final drive.
Al Hamilton
76 Eleganza II
Kingston, Ont
Where did you get your gears??
Paul Bartz
From: Al Hamilton
Sent: 1/15/00 10:25 AM
Emery,
The 3.70:1 ratio came from changing both gears or sprockets at the
rear
of the transmission and using the original chain and 3.07 final drive.
Al Hamilton
76 Eleganza II
Kingston, Ont
Larry
Please e-mail me off net. I have something that could be of a great value to
your team.
Wayne Newland F9300 75 Palm Beach Columbia, Md
> I have, I guess, the equivalent of a 3.90 final drive ratio, due to the fact
> that I have the 3.42 + the 3.50 sprockets. This is my first report of that
> installation, cause, gosh, I haven't gone anywhere. Last week drove to Des
> Moines from Springfield, about 6.5 hours each way, hilly and flat. To true
> out at 60 mph, my tach reads 2900 rpm. No milage figures untill friday when I
> fill her up from the last trip and before my departure Saturday for Terre
> Haute (remember I go to womens b-ball games in the winter with my coach). I
> still don't know if I did the right thing having Danny Dunn install the 3.50
> when he built my tranny. I used the advice of a Flatlander club member who
> had the same installation and also the article in GMCMM about this
> combination. I am sure I can pull a small house up a hill on skids which
> provides a great sense of security after the fiasco of being stuck on a hill
> in the Black Hills. The noise level increase at cruise is not noticable. The
> fact that I go down the road at 3 grand..........jury is out. I never drove
> the old girl faster than 62 anyway. She hardly ever shifts down. I will keep
> you all posted. Larry in MO, 75 PB
Please e-mail me off net. I have something that could be of a great value to
your team.
Wayne Newland F9300 75 Palm Beach Columbia, Md
> I have, I guess, the equivalent of a 3.90 final drive ratio, due to the fact
> that I have the 3.42 + the 3.50 sprockets. This is my first report of that
> installation, cause, gosh, I haven't gone anywhere. Last week drove to Des
> Moines from Springfield, about 6.5 hours each way, hilly and flat. To true
> out at 60 mph, my tach reads 2900 rpm. No milage figures untill friday when I
> fill her up from the last trip and before my departure Saturday for Terre
> Haute (remember I go to womens b-ball games in the winter with my coach). I
> still don't know if I did the right thing having Danny Dunn install the 3.50
> when he built my tranny. I used the advice of a Flatlander club member who
> had the same installation and also the article in GMCMM about this
> combination. I am sure I can pull a small house up a hill on skids which
> provides a great sense of security after the fiasco of being stuck on a hill
> in the Black Hills. The noise level increase at cruise is not noticable. The
> fact that I go down the road at 3 grand..........jury is out. I never drove
> the old girl faster than 62 anyway. She hardly ever shifts down. I will keep
> you all posted. Larry in MO, 75 PB
Paul,
The two gears and modified cover were done here in Ontario. Only a
limited number, about 15 sets, have been made and none in the last two
years. Some are being made this winter, I think. The seller wants the old
gears and cover as cores, as well. If you want any more details email me
separately and I'll put you in touch with him.
Al Hamilton
76 Eleganza II
Kingston, Ont
The two gears and modified cover were done here in Ontario. Only a
limited number, about 15 sets, have been made and none in the last two
years. Some are being made this winter, I think. The seller wants the old
gears and cover as cores, as well. If you want any more details email me
separately and I'll put you in touch with him.
Al Hamilton
76 Eleganza II
Kingston, Ont
I guess I missed something here. In a past post, Al Hamilton said:
"The 3.70:1 ratio came from changing both gears or sprockets at the rear
of the transmission and using the original chain and 3.07 final drive."
Are these like Caspro's 3.55 gears, or something different? Also, where
would I get them and how much?
Dave (& Dege), '76 Royale, Santa Barbara, CA
"The 3.70:1 ratio came from changing both gears or sprockets at the rear
of the transmission and using the original chain and 3.07 final drive."
Are these like Caspro's 3.55 gears, or something different? Also, where
would I get them and how much?
Dave (& Dege), '76 Royale, Santa Barbara, CA
Arch several times I have seen 4.11 gears mentioned when talking about the
gearing for the GMC motorhome, including your response here. I don't really
see what the relevance is. I dont believe you can compare the final drive of
the GMC against an olds 442 with the same engine. The tires are different
size, tranny gearing is different. Am I missing something?
>In a message dated 01/16/2000 10:43:50 AM Central Standard Time,
>>
>> I have, I guess, the equivalent of a 3.90 final drive ratio, due to the
>fact
>> that I have the 3.42 + the 3.50 sprockets. This is my first report of that
>>
>Larry
>
>Please tell us what tires and wheels you have so some of these
>engineering types can tell us what you are riding on. I just cant
>believe that you are that far off since many camper trucks run 4.11
>gears. I guess you realize that by running at a higher RPM you should
>not need the high volume oil pump (never have understood putting in
>high volume oil pumps and restrictors). Bet you could also get by with
>a Cinnabar (stamped steel) water pump since you are cranking more RPMs.
>Man now this is getting exciting. I sure hope your fill-up will have good
>things to say to us. Yes, I know you need lots of miles to get a good reading
>but I am just looking for a clue. Just need to know how far I can let the
>vacuum advance run out. Also have to find us a portable dyno. We are
>getting down to the nubbins here.
>
>Take Care
>Arch
>
>
gearing for the GMC motorhome, including your response here. I don't really
see what the relevance is. I dont believe you can compare the final drive of
the GMC against an olds 442 with the same engine. The tires are different
size, tranny gearing is different. Am I missing something?
>In a message dated 01/16/2000 10:43:50 AM Central Standard Time,
>>
>> I have, I guess, the equivalent of a 3.90 final drive ratio, due to the
>fact
>> that I have the 3.42 + the 3.50 sprockets. This is my first report of that
>>
>Larry
>
>Please tell us what tires and wheels you have so some of these
>engineering types can tell us what you are riding on. I just cant
>believe that you are that far off since many camper trucks run 4.11
>gears. I guess you realize that by running at a higher RPM you should
>not need the high volume oil pump (never have understood putting in
>high volume oil pumps and restrictors). Bet you could also get by with
>a Cinnabar (stamped steel) water pump since you are cranking more RPMs.
>Man now this is getting exciting. I sure hope your fill-up will have good
>things to say to us. Yes, I know you need lots of miles to get a good reading
>but I am just looking for a clue. Just need to know how far I can let the
>vacuum advance run out. Also have to find us a portable dyno. We are
>getting down to the nubbins here.
>
>Take Care
>Arch
>
>
I think you are right Em about faster engine wear at higher RPMS and that is
one of the things I have been really bothered about. I want reliability
more than performance. I believe the wear on the 455 (since it is a long
stoke engine) increases logarithmically instead of directly proportiuonal to
the engine RPMs.
If I remember the mechanical engineers always talked about piston feet per
mile as one indicator of engine wear.
>
>
>if we let the ladies run a little higher RPM maybe we would not need
>high volume water and oil pumps. >>
>
>Arch & Tom (and others) -- I have a question. I installed a 3.55 to 1
>final drive this fall but had not yet been on a long trip. We'll be leaving
>for Fla. the middle of Feb. It seems great the little bit I have used it.
>
>My question: Wouldn't we expect a GMC engine to wear faster if it is run for
>long periods at 3000 or higher RPM versus running for the same hours at say
>2500 RPM?
>
>It really seems that this would be the case. Anyone have comments?
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
>
>
one of the things I have been really bothered about. I want reliability
more than performance. I believe the wear on the 455 (since it is a long
stoke engine) increases logarithmically instead of directly proportiuonal to
the engine RPMs.
If I remember the mechanical engineers always talked about piston feet per
mile as one indicator of engine wear.
>
>
>if we let the ladies run a little higher RPM maybe we would not need
>high volume water and oil pumps. >>
>
>Arch & Tom (and others) -- I have a question. I installed a 3.55 to 1
>final drive this fall but had not yet been on a long trip. We'll be leaving
>for Fla. the middle of Feb. It seems great the little bit I have used it.
>
>My question: Wouldn't we expect a GMC engine to wear faster if it is run for
>long periods at 3000 or higher RPM versus running for the same hours at say
>2500 RPM?
>
>It really seems that this would be the case. Anyone have comments?
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
>
>
mmm..
that's very interesting. It makes sense to me and makes
me wonder about the wisdom of changing the ratio of my
drive train. I have nothing to complain about regarding
the performance of my GMC except for gas mileage.
Maybe if could add overdrive then the higher ratio would
make more sense.
Richard Waters '76 PB, Troy, MI
> I think you are right Em about faster engine wear at higher RPMS and that is
> one of the things I have been really bothered about. I want reliability
> more than performance. I believe the wear on the 455 (since it is a long
> stoke engine) increases logarithmically instead of directly proportiuonal to
> the engine RPMs.
>
> If I remember the mechanical engineers always talked about piston feet per
> mile as one indicator of engine wear.
>
that's very interesting. It makes sense to me and makes
me wonder about the wisdom of changing the ratio of my
drive train. I have nothing to complain about regarding
the performance of my GMC except for gas mileage.
Maybe if could add overdrive then the higher ratio would
make more sense.
Richard Waters '76 PB, Troy, MI
> I think you are right Em about faster engine wear at higher RPMS and that is
> one of the things I have been really bothered about. I want reliability
> more than performance. I believe the wear on the 455 (since it is a long
> stoke engine) increases logarithmically instead of directly proportiuonal to
> the engine RPMs.
>
> If I remember the mechanical engineers always talked about piston feet per
> mile as one indicator of engine wear.
>
Wern't we previously told that the engine block had such a high nickel
content that wear was not a problem???
Paul Bartz
From: Tom Warner
Sent: 1/17/00 12:56 PM
I think you are right Em about faster engine wear at higher RPMS and
that is
one of the things I have been really bothered about. I want reliability
more than performance. I believe the wear on the 455 (since it is a
long
stoke engine) increases logarithmically instead of directly
proportiuonal to
the engine RPMs.
If I remember the mechanical engineers always talked about piston feet
per
mile as one indicator of engine wear.
>
>
>if we let the ladies run a little higher RPM maybe we would not need
>high volume water and oil pumps. >>
>
>Arch & Tom (and others) -- I have a question. I installed a 3.55 to
1
>final drive this fall but had not yet been on a long trip. We'll be
leaving
>for Fla. the middle of Feb. It seems great the little bit I have used
it.
>
>My question: Wouldn't we expect a GMC engine to wear faster if it is
run for
>long periods at 3000 or higher RPM versus running for the same hours at
say
>2500 RPM?
>
>It really seems that this would be the case. Anyone have comments?
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
>
>
content that wear was not a problem???
Paul Bartz
From: Tom Warner
Sent: 1/17/00 12:56 PM
I think you are right Em about faster engine wear at higher RPMS and
that is
one of the things I have been really bothered about. I want reliability
more than performance. I believe the wear on the 455 (since it is a
long
stoke engine) increases logarithmically instead of directly
proportiuonal to
the engine RPMs.
If I remember the mechanical engineers always talked about piston feet
per
mile as one indicator of engine wear.
>
>
>if we let the ladies run a little higher RPM maybe we would not need
>high volume water and oil pumps. >>
>
>Arch & Tom (and others) -- I have a question. I installed a 3.55 to
1
>final drive this fall but had not yet been on a long trip. We'll be
leaving
>for Fla. the middle of Feb. It seems great the little bit I have used
it.
>
>My question: Wouldn't we expect a GMC engine to wear faster if it is
run for
>long periods at 3000 or higher RPM versus running for the same hours at
say
>2500 RPM?
>
>It really seems that this would be the case. Anyone have comments?
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
>
>
Rick I believe cylinder wear is log proportional to the number of feet per
minute the piston is moving against the cylinder wall. We don't really have
a problem with main and rod bearing wear since those are easily replacable.
The cylinder bores are another story however.I think in most cases coach
owners get their 455 cylinder bores rebored to a larger size when they do
not need to. With many builders it is just routine. Not a good idea
however. The 455 bores are so hard that they seldom are out of round and
can be simply reringed or forged standard pistons replaced .
Want to really reduce cylinder bore wear add a supercharger.
>
>> Wouldn't we expect a GMC engine to wear faster if it is run for
>> long periods at 3000 or higher RPM versus running for the same hours at
>say
>> 2500 RPM?
>>
>
>Emery,
> In worst case it might wear 20% faster (3000-2500=500/2500=0.20). In
>reality, if you can run at a smaller throttle opening due to the lower
>gearing, thereby lowering the BMEP (pressure applied to the piston on each
>power stroke), you would at least reduce some of the cylinder and ring wear.
>In the end I think you'd have slightly more wear, but not much. That's my
>SWAG.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>
minute the piston is moving against the cylinder wall. We don't really have
a problem with main and rod bearing wear since those are easily replacable.
The cylinder bores are another story however.I think in most cases coach
owners get their 455 cylinder bores rebored to a larger size when they do
not need to. With many builders it is just routine. Not a good idea
however. The 455 bores are so hard that they seldom are out of round and
can be simply reringed or forged standard pistons replaced .
Want to really reduce cylinder bore wear add a supercharger.
>
>> Wouldn't we expect a GMC engine to wear faster if it is run for
>> long periods at 3000 or higher RPM versus running for the same hours at
>say
>> 2500 RPM?
>>
>
>Emery,
> In worst case it might wear 20% faster (3000-2500=500/2500=0.20). In
>reality, if you can run at a smaller throttle opening due to the lower
>gearing, thereby lowering the BMEP (pressure applied to the piston on each
>power stroke), you would at least reduce some of the cylinder and ring wear.
>In the end I think you'd have slightly more wear, but not much. That's my
>SWAG.
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
>
