Gear Vendors Finally Coming!

[87MH]

Originally Posted by GlenCoombe

...Having the performance figures for the 454 sure would be cool if anybody can find them...

Below are two that I have archived…





The First (white background) is for a 454 HO engine that I think is fairly representative (but a bit on the high side) of the 454’s (7.4 liter) engines in most of the mid 80’s MoHos. Note that max torque (about 500 ft.lbs.) occurs at about 3350 rpm – max horsepower (420 HP) is at engine redline of 5250.

The engine which was dyno'ed has a compression ratio of 8.75 to one, requiring a 92 Octane (Premium) gas rating from the manufacturer.





Compare to the second (black background) curve – a modern 8.1 liter FI engine installed in the Workhorse Chassis. Max torque of 450 or so is flat between 3500 and 3000 rpm. Max HP of 340 is about 4200 rpm.

Note that where the HP and Torque graphs cross are totally meaningless due to the differing scales on the y axis.

I need to reiterate my opinions stated in a previous post – the carbureted 454 does not have enough oomph to warrant the installation of a gear reduction unit in a large motor home….AND…thorough and complete gas mpg records (recording EVERY gallon of gas and mileage between fill ups) should be documented for a representative number of miles prior to installing the reduction gearing. A good record – before and after - of mpg and time to 60 mph or time to ¼ or ½ mile markers from a standing stop would reveal the real benefit (or performance loss) of an expensive gear reduction installation.

[noiva]

Originally Posted by 87MH

Below are two that I have archived…





The First (white background) is for a 454 HO engine that I think is fairly representative (but a bit on the high side) of the 454’s (7.4 liter) engines in most of the mid 80’s MoHos. Note that max torque (about 500 ft.lbs.) occurs at about 3350 rpm – max horsepower (420 HP) is at engine redline of 5250.

The engine which was dyno'ed has a compression ratio of 8.75 to one, requiring a 92 Octane (Premium) gas rating from the manufacturer.





Compare to the second (black background) curve – a modern 8.1 liter FI engine installed in the Workhorse Chassis. Max torque of 450 or so is flat between 3500 and 3000 rpm. Max HP of 340 is about 4200 rpm.

Note that where the HP and Torque graphs cross are totally meaningless due to the differing scales on the y axis.

I need to reiterate my opinions stated in a previous post – the carbureted 454 does not have enough oomph to warrant the installation of a gear reduction unit in a large motor home….AND…thorough and complete gas mpg records (recording EVERY gallon of gas and mileage between fill ups) should be documented for a representative number of miles prior to installing the reduction gearing. A good record – before and after - of mpg and time to 60 mph or time to ¼ or ½ mile markers from a standing stop would reveal the real benefit (or performance loss) of an expensive gear reduction installation.

Dennis,

Even though I couldn't get your graphs to display, I am trying to make sure I understand as fully as possible what you're saying. Of course, in my case the order has been placed. By "gear reduction" are you talking about only the underdrive? My problem really isn't lower gearing, but the need for a taller overdrive due to the 5.29 axle. It's impossible for me to travel above 55 mph without revving the engine and causing it to produce too much heat. I am looking for a "taller" gear for cruising at around 65 mph without putting such a strain on the engine, cooling system, and transmission. By going to the .78 overdrive the engine will run cooler, less strain on the rpms, and the transmission won't be as hot nor as stressed. Do you agree with this? I've gotten dozens of communications from people with all kinds of vehicles, including large carbed, 3-speed, MoHos, who use the GV overdrive and are full of praise for how much better their vehicles run.

Thanks,

Thanks,

[guy99]

Dennis,
I, too, am unable to see the graphs.

[87MH]

Originally Posted by noiva

...I couldn't get your graphs to display....

Sorry about the graphs - they were and still are visible in the original post on my access to the Forums....

They are re-posted below - the first, the white one, is a 454 HO engine (about a '91 Block design) with a carbureted intake design (4 bbl) - should be fairly comparable to the '80's engines except for the compression ratio.

The second (black background) is from the Workhorse site - new manufacture 8.1 Liter (494 cubic inch) engine.

Originally Posted by noiva

...By going to the .78 overdrive the engine will run cooler, less strain on the rpms, and the transmission won't be as hot nor as stressed. Do you agree with this?

Tim:

No, I do not agree with your assumptions. On my '87 345 I have a VERY difficult time keeping the vacuum gauge in the upper teens on a level grade (LOTS of level grades in my part of Texas...Planet Houston)....this indicates to me that the engine requires a healty dose of 4 bbl almost all of the time. In addition, I have very low torque in the 2300 to 2500 rpm range - this is the range the torque converter in the transmission is "slipping" to convert engine rpm to a lower rpm going to the "inlet" of the 3 speed transmission. Above 2500 rpm the speed of the engine varies directly with the speedometer, below (or at) 2500 rpm the speedometer can drop lower while the torque converter permits the engine to stay at 2300 to 2500 rpm. Below 2300 the tranny will grab the next lower gear.

Again, in my opinion, the lower effective gear ratio will put a higher work and thermal load on both the tranny AND the engine of any Classic MoHo.

Now, my '87 has almost ALWAYS carried close to 16,000 lbs all of the time, and, my 454 has close to 80,000 miles on it. Perhaps (almost certainly) a speed reduction unit would benefit other types of vehicles - it would be ideal for a vehicle that runs light most of the time, and heavily loaded just sometimes (as in a one ton pickup used for "commuter" service during the week, and then to tow a huge and heavy trailer during the weekends), when loaded, the speed reduction unit could effectively raise the rear end ratio and put less of a strain on the engine (let run it at higher rpm's for a given load) whenever the vehicle is required to carry a "heavy" (heavier than normal) load.

In other words, on my '87, at 16,000 lbs, the one-ton P-32 Chassis and drivetrain are maxed out ALL of the time, and by noting my rpm gauge, vacuum gauge, and the performance of the drive train at 55, 60, and 65 on various grades (there is a "sweet spot" between 60 and 63 mph - where the engine is turning over about 3000 rpm, give or take 100) I have inferred that the GM engineers have placed the correct final drive ratio in the chassis - I do not believe I could benefit by a lower ratio final drive.

On the mileage (mpg) question - I can only state that my mpg varies widely. I do not have an explanation for this variance - I try to drive consistently all of the time - 60 to 63 with one eye on the vacuum guage. I can only state that keeping track of each gallon of gas on each and every fillup is the only way to accurately determine overall efficiency and your true gas mileage. I hope others would post their mileage-gas used records over a long interval. One tank "snapshots" are not that accurate, in my opinion.

My opinion by my observations only, but I will also be very curious as to the outcome of any final drive ratio modification on the Airstream Classic MoHo's.

In all honesty, I find it unusual that none of the regular posters with MoHo's here (to my knowledge) has done such an installation.

Please let my know if the two pics have uploaded successfully - as I said earlier, the pics are visible in my original posting when I open it.

Luck.

[3Ms75Argosy]

as I've always wondered what a "in between" gear would do for my TV with trailer. I have a Dodge B350 van with a 5.9L V8 and a four speed OD tranny. The rear end is something like a 4.19 (Dodge gears seem to be a bit different than Chevy's, but I digress). Although I don't have a tach, I know I spin probably around 3000 rpms at 65 mph, probably around 3500 at 70 in third. In OD (which I'm not supposed to tow in anyway) I can't tow with this gear at all, the engine bogs down, and speed drops. It won't pull even at 65 mph. I think the OD drops about 1000 rpms at 70. Downhill, the engine will pull fine at 70mph (dUH!) in OD.

I do wonder if I had JUST a tad lower gear (something between 3rd and OD) if that would let me get more miles to the gallon. I get 8 mpg usually pulling (9 if I really baby it). However, that 3rd gear pulls our 5500 # trailer around just fine. I do notice too that if I hit a hill at around 70 (turning about 3500 rpms) that I can get up it just fine. If I go around 60, I'll be shifting down to 2nd at 50mph in no time.

I never (knock on wood) have overheated even pulling at 65mph through 113 degree heat, or pulling up the Grapevine in that same heat (AC off though).

I guess Dodge did their homeowork, but I can't help but guess at what a slightly different gear might do.
Marc

[noiva]

Guy,

Thanks so much for taking the time to republish the graphs (They came up this time), and particularly for sharing your experience and expertise in such detail.

My knowledge of the 370 is based on lots of research, but not that much experience. The general assumption about the reasoning for the very low axle of 5.29 (much lower than the 454s tended to come with) is that the Gillig chassis, extra weight, and load capacity (18,500 lbs. GCVWR) is why Gillig used such a low gear. It was also assumed that speeds were lower in the 80s, and there would be no reason to routinely travel at 60-65 mph, as there is today. My "sweet spot" is between 50-55 with vacuum readings around 12. Anything above that causes the engine to rev over 3000 rpms (even though peak torque is 2200), heat begins to rise, vacuum drops to 10 or below, and it's quite obvious the whole drive train is under stress. The RV shop that does the things I can't do (major mechanical stuff) has told me from the beginning that the only problem they could see with the 370 set-up was it needed one more gear (overdrive).

I guess I'm having a tough time understanding why it won't be beneficial when I'm running above 55, keeping in mind that the GV can be cut on and off anytime. By the way, I do keep very close records on gas mileage, and my limited trips have produced widely varying figures, as you mentioned with yours. Tops has been 8.6, and low around 6. Frankly, however, my travel has been too limited to give a reliable average. I've put barely 2000 miles on the MoHo in almost 3 years, although it's picking up now that I actually own it.

Would you consider it possible that the 370, at least, may be the exception to your opinion that the Classics don't routinely need another gear? It is an odd set-up, so to speak.

Thanks,

[guy99]

Tim,
You addressed your message to me but it was Dennis who posted this very useful information.

[87MH]

Originally Posted by noiva

...about the reasoning for the very low axle of 5.29 (much lower than the 454s tended to come with) ....My "sweet spot" is between 50-55 with vacuum readings around 12. Anything above that causes the engine to rev over 3000 rpms (even though peak torque is 2200), heat begins to rise, vacuum drops to 10 or below, and it's quite obvious the whole drive train is under stress....I guess I'm having a tough time understanding why it won't be beneficial when I'm running above 55, keeping in mind that the GV can be cut on and off anytime....on gas mileage, and my limited trips have produced widely varying figures, as you mentioned with yours. Tops has been 8.6, and low around 6...

Tim:

It's interesting that your Ford drivetrain turns 55 mph at 3000 rpms with a 5.29 rear end, and the P-32 delivers the same 3000 rpms at 60 with a 4.56 rear end.

Doing a little math results in the fact that you are turning about 3272 engine revolutions per mile, while I am doing about 3000 revs per mile -

5.29/4.56 = 1.16

3272/3000 = 1.09

Close enough taking into account the accuracy of the tachs and the "about" readings.

With your vacuum dropping off above 55, it indicates to me that the engine is fully loaded at this speed (at 3000 rpm), and forcing it to deliver the same horsepower at a lower rpm (by installing an accessory gear) will do three things -

First: - It will INCREASE the heat load to the radiator, since you want to produce the same horsepower at a lower rpm - this will require a more open throttle in order to pass an additional amount of gas to the engine at a lowered rpm. This will also lower the amount of water circulating through the engine (since the water pump will also be turning slower), all of this lowers your engine vacuum, and you are closer to "lugging" your engine with the higher specific horsepower requirement at a lower rpm.

Second: - It will also INCREASE the transmission heat and wear since you will be forcing the tranny to operate closer to the "torque multiplier" speed of 2500 rpm. - In other words, the transmission is doing more work at lower speeds, causing a higher specific heat buildup per mile travelled.

Third: - It will cause you to get WORSE mileage per gallon of gas. This is due to the fact that the gear reduction will PROBABLY cause your vacuum to drop, pulling the engine mixture to an "over-rich" condition, thereby lowering efficiency. This all falls in with the concept of requiring more horsepower (pushing the vehicle faster) at a reduced engine speed - given that the engine is probably loaded close to optimum conditions right now (you stated that any faster speeds rapidly drop your vacuum reading). The same power requirements at a lower engine speed will assuredly cause your vacuum to drop even lower at a lower engine speed with a higher horsepower output requirement.

Your range of mileage is about the same as mine, with my average about 7.2 mpg.

One good thing about the unit you are planning to install - you can always go back to the original gearing with the flick of a switch. I haven't used a Gear Vender or similar, but having driven split gear rear ends it took about twice as long to switch the rear end ratio as it took to grab another gear, so "split shifting" required quite a bit of time between clutch out to clutch out (power on to power on) - too much time to be beneficial when going up a steep grade.

Good luck on your installation, please post as accurate before and after performance numbers as possible. There are many of us interested in increasing the longevity and performance of our units.

[noiva]

Originally Posted by guy99

Tim,
You addressed your message to me but it was Dennis who posted this very useful information.

Guy,

My apologies. I'd like to believe that was a result of thinking faster than I can type, but it's most certainly not paying close enough attention .

Thanks,

[noiva]

Dennis, (I think I at least got your name right this time )

I'm quite anxious to see how this works out, and will keep you informed. At least I have a 30-day, no questions asked return policy if this does, indeed, cause the lugging you've mentioned, or any of the problems like heat, etc. Secondly, I still have to go back to the very low (2200 rpm) range of peak torque on the 460 Ford vs quite a bit higher for the 454 Chevy, as well as I can't think of any other way to get this rolling blimp to move faster than 55.

Thanks so much for your input. If you come up with other material related to this issue, I'd love to hear it.

Best,

[GlenCoombe]

Dennis, I'm confused... but that's not anything new. You wrote "(there is a "sweet spot" between 60 and 63 mph - where the engine is turning over about 3000 rpm, give or take 100) I have inferred that the GM engineers have placed the correct final drive ratio in the chassis - I do not believe I could benefit by a lower ratio final drive.)"
To me that sounds like you conclude that your top speed should then be 60-63 mph. If on todays interstate highways you want to keep up with traffic at 70-74 mph and you can turn 3000 rpm's doing so how does this not make sense?
Other than wind tunnel data we don't have ...to say that the aerodynamic drag at that speed is going to defeat fuel economy my contention (without being contentious) is that in some cases the addition of gear splitting is valid.
Remember this is not an axel splitter but a true aux. transmission that enables shorter shifting in the appropriate rpm range.
For me time is money, my rig runs daily. If I can go down the road faster AND / OR more economically without luggin my engine, how do I loose?
The best case in point is all the newer coaches that went to four speed transmissions. The extra gear ment higher speeds and lower rpms.
Today I beat feet up I-77 and at 73mph was turning 3200 rpms... to fast an engine speed for my liking. If I could do that speed at say 27-2800 rpms I wonder what my fuel savings, if any, would be. I know that during the heat of the day in summer that would have me running engine temp in the 205-210 range vs. 190 at 27-2800 rpm.
The 370 Gillig chassis in question for Tim is actually a city bus chassis geared for moving heavy loads at city stop and go speeds. The 5.29 rear end was never ment for highway use. An overdrive gear of modest gain is certainly in order for Tim's intended use.

[GlenCoombe]

Hmmm....got awful quiet on this thread, didn't it? Tim has your new unit come in yet???? huh, Huh!?? I'm so excited. Also have you had time to hunt down the new/alternate driveshaft?

[noiva]

Originally Posted by GlenCoombe

Hmmm....got awful quiet on this thread, didn't it? Tim has your new unit come in yet???? huh, Huh!?? I'm so excited. Also have you had time to hunt down the new/alternate driveshaft?

Silence did become almost audible, didn't it? Could be several reasons, I guess. Incidentally, I just got confirmation the unit was shipped from CW (10% discount, but handled with a P.O. by GV ). No time yet to look for driveshaft, but looks like I'll have the GV unit sooner than expected. CW is usually very quick with their shipping. I'll keep you posted. Got to remember to take pictures .

Best,

[GlenCoombe]

Wow Tim, I hadn't even thought about the President's Club discount from Camping World! That's one way to justify the membership I'd say. If only they could be trusted to install it.....

[noiva]

Originally Posted by GlenCoombe

Wow Tim, I hadn't even thought about the President's Club discount from Camping World! That's one way to justify the membership I'd say. If only they could be trusted to install it.....

Glen,

This is one time the cost of PC has been worth it. GV does not offer their trannies at a discount ever, but they're the ones who suggested they P.O. it through CW since I was a member of the PC. I never even contacted CW. They sent me an email today saying the GV unit had been shipped!

Install - I've been told repeatedly that any good transmission shop can do this job, and that it's not that difficult. They should also know a good shop that does the machine work on the drive shaft. Any good transmission shops in your area?

[ALANSD]

a related question...what kind of fuel mileage could I expect out of a 460 in a f250? Articles say this engine gave a combination of durable power and fuel efficiency, but I don't find any approx numbers.

[wanderingeye]

This is a very important thread for all classic owners. It's an empirical test we can all learn from. The GV's extra gears will undoudtedley apply the engines power and torque more efficiently into forward motion. The power to wieght ratio ,however, of this particular vehicle may make the fuel savings marginal. I'll be very interestd in the outcome. Cheers Tom

[noiva]

Originally Posted by wanderingeye

This is a very important thread for all classic owners. It's an empirical test we can all learn from. The GV's extra gears will undoudtedley apply the engines power and torque more efficiently into forward motion. The power to wieght ratio ,however, of this particular vehicle may make the fuel savings marginal. I'll be very interestd in the outcome. Cheers Tom

Tom,

I'll keep you posted. I really am not doing this primarily for fuel savings, if you've been following the thread. I suspect there's only so much to be done with a front engine gaser that weighs almost 18,000 lbs. My main purpose is the power and torque applications. Six speeds have to be better than 3, especially with that 5.29 axle. It should come in this week, but I'm leaving Sat. for a week, so it will probably be after July 16 before the installation .

Best,

[MrGoate]

Greetings All; pleasantly mild here today. Been on the road, so am offering my three cent a bit late in the game...

Was fortunate enough to have acquired our Classic with both Banks and GearVendor already in place. While we're not mechanical experts, even less familiar with figures or graphs, what we can tell you from practical experience: you'll LOVE it!

With the GearVendor overdrive, our coach runs around 2200 rpm at 60 mph, perhaps 2500 rpm at 70 mph (yes, we've had to watch our speed) with absolutely no extra effort or laboring of the engine. Temp-wise we always run a cool 160-180, this mostly dependent on the ambient, and at 60-62 mph achieve a consistent 8-8.5 mpg w/o toad. Torque is fantastic, pulling the Grapevine a piece of cake; we've had no mechanical issues whatsoever.

The difference in sportscar-like performance of our Classic's Banks, GearVendor setup vs. our previous coach with stock 454/3spd (which, at 55 mph, seemed to peak out at a loud 3000 rpm) is like day and night; we wouldn't own another coach without both or, at the very least, the GV gearsplitter and wholeheartedly encourage all Classic owners to consider same. Here's wishing you success - and continued safe travels - with your GearVendor installation.

[noiva]

Originally Posted by MrGoate

Greetings All; pleasantly mild here today. Been on the road, so am offering my three cent a bit late in the game...

Was fortunate enough to have acquired our Classic with both Banks and GearVendor already in place. While we're not mechanical experts, even less familiar with figures or graphs, what we can tell you from practical experience: you'll LOVE it!

With the GearVendor overdrive, our coach runs around 2200 rpm at 60 mph, perhaps 2500 rpm at 70 mph (yes, we've had to watch our speed) with absolutely no extra effort or laboring of the engine. Temp-wise we always run a cool 160-180, this mostly dependent on the ambient, and at 60-62 mph achieve a consistent 8-8.5 mpg w/o toad. Torque is fantastic, pulling the Grapevine a piece of cake; we've had no mechanical issues whatsoever.

The difference in sportscar-like performance of our Classic's Banks, GearVendor setup vs. our previous coach with stock 454/3spd (which, at 55 mph, seemed to peak out at a loud 3000 rpm) is like day and night; we wouldn't own another coach without both or, at the very least, the GV gearsplitter and wholeheartedly encourage all Classic owners to consider same. Here's wishing you success - and continued safe travels - with your GearVendor installation.

Thanks so much for the encouragement! I've weighed this issue for almost 2 years. The GV is very expensive, but I finally decided it was that, resign myself to 55 mph ALL the time, or sell the coach. Since I got the coach from my brother , I figured I could stretch the budget and get the gears . The 370 has a Ford 460 with a Gillig chassis which will NOT allow the Banks to fit, so I'll have to settle for the GV. So glad to hear it's probably the better of the two IF one has to choose. I'll be posting the changes, and some pics , when this gets done.

By the way, it's 95 degrees here today. A far cry from pleasantly cool .

Best,