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Old 06-16-2006, 06:28 PM   #1
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Gear Vendors Finally Coming!

Well, after researching for about 6 months, I finally bit the bullet ($) and ordered a Gear Vendors over/under drive gear set for my 1989 370. I had sought opinions earlier from Forum members, and the response was to go for it. I should get it in about 2 weeks, and I have a tranny shop owner who is a neighbor. He's already excited about putting it in. I'll keep photos of the before and after, and write what I experience in performance/gas mileage changes, if any, once it's installed. Just for the record, the 370 came with a Ford 460, C-6 3-speed, and a 5.29 rear axle ! Can't get much over 55 without really maxing her out. That really puts a crimp in traveling interstates and such - since I have a choice of holding everyone up, or messing up my MoHo .
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Old 06-16-2006, 07:49 PM   #2
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Thumbs up Great Choice!

Hi Tim,

You will love that Gear Vendor. I had an old heavy duty Grumman Step Van with 8000lb capacity 15 or so years ago that had 6.67 gears in it and while it would run at 65mph empty or fully loaded, the engine was really whining. I added the Vendor and the new max was 75 or so and the rpm's dropped substantially.
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Old 06-17-2006, 01:17 AM   #3
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I fully agree- one of the best creations ever, for a tow vehicle, or just for running around. Never had one in an RV, but can imagine the combo you have and the improvement you'll enjoy. I inherited one in a used truck in California, and MAN, what a great thing to have! I'm surprised by how NO ONE in the East is really familiar with these- but I think that the rise in fuel prices will spur that on a little.
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Old 06-17-2006, 06:48 AM   #4
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Tim, we do really expect a FULL photo essay on the installation! This will be a great thread for all of us to watch. Now, do you have the numbers of the before installation down? RPM vs. SPEED? MPG vs. SPEED?
I just wish you had a 454 so I could get the scoop for my use.
Does your neighbor do drive shaft balancing too? Gotta make it perfect...stem to stern....perhaps a new pinion seal too while you're at it...new U-Joints....on and on.
I'm waiting with baited breath...just call me TUNA!
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Old 06-17-2006, 08:15 AM   #5
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Quote:
Originally Posted by GlenCoombe
Tim, we do really expect a FULL photo essay on the installation! This will be a great thread for all of us to watch. Now, do you have the numbers of the before installation down? RPM vs. SPEED? MPG vs. SPEED?
I just wish you had a 454 so I could get the scoop for my use.
Does your neighbor do drive shaft balancing too? Gotta make it perfect...stem to stern....perhaps a new pinion seal too while you're at it...new U-Joints....on and on.
I'm waiting with baited breath...just call me TUNA!
Lew, Millionairstream, and Glen,

Thanks for all the encouragement. I will admit I've been very slow to finally do this. The more I've driven the 370, the more I've been convinced I didn't have much choice. Current figures are just about 3,000 rpms at 55 mph, with just a little variation going to 60 mph. Simply way too many rpms for that speed cruising. Interstates at 65 are really hairy. Engine is screaming, and heat level rises rather quickly over 55 mph. I've done all I know to cool things off, but there's no getting around the rpm problem. It's true that they are not used as often here in the East. I don't know why either, but maybe I'll start a trend . Gas mileage has been difficult to pin down except I can tell you that I got about 8.6 mpg this past spring on a trip that did not call for air conditioning, outside temps in the 70s, and a fairly light load in the MoHo. I know it drops with increasing outside temps, running the AC, and loading - but I really don't know just how much. So far, I haven't run long enough distances to give me accurate figures. Also, whether I run the generator makes a difference too.

With only 17,000 miles on the MoHo, I don't appear to need full replacement of the drive line seals, U - joints, etc, but I'm going to get my neighbor to give me his opinion while he does this job. The drive shafting is going to be done at a shop that specializes in cutting and balancing drive shafts. Had a long talk (for the second time) with the folks at Gear Vendors yesterday, and basically all their gear sets are the same. Only the housings, speedo gears, etc., are different to match various vehicles. They said I could even remove the gear set if I sold the MoHo, and put it on any other vehicle just by ordering the matching attachments! I doubt I would do that, but it was interesting. The 454 vs 460 issue sounds like more of a gear ratio question than a power train problem - Glen . I have no idea what your axle ratio is, but if it's anything close to mine (5.29) I should think it would make driving much more pleasant.

The final deciding factor was the two lower gears, giving a true 6-speed automatic if I chose to run that way. It's supposed to really help with long climbs and towing - giving much smoother shifting since the gaps are so much less between gears - another issue causing me to go with this set-up.

Thanks for the support . I'll do my best to keep good pictures, and report on results .

Best,
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Old 06-17-2006, 09:46 AM   #6
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Tim, I turn about 2900 rpm's at 65 so I'm a lot better off to start. That said I'd like about 500 rpm's of relief or so at the top end as I'm certain that would be the difference for me in fuel economy. 65 mph is about what I like to do unless I'm in a real hurry or traffic is getting goofy.
Any idea what the labor cost is going to run you? Drive shaft cut and rebalance? Details, details...
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Old 06-17-2006, 10:13 AM   #7
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Originally Posted by GlenCoombe
Tim, I turn about 2900 rpm's at 65 so I'm a lot better off to start. That said I'd like about 500 rpm's of relief or so at the top end as I'm certain that would be the difference for me in fuel economy. 65 mph is about what I like to do unless I'm in a real hurry or traffic is getting goofy.
Any idea what the labor cost is going to run you? Drive shaft cut and rebalance? Details, details...
Glen,

According to the Gear Vendors material, you should have a .78 ratio compared to the 1:1 you are now getting in 3rd gear. You can do the math, but it will slow your rpms down to just over 3/4 of what you're now turning. I like to run about 65 as well, and the rpm reduction should allow me to do that, not to mention running cooler. Labor is going to be about $200, not including the shaft cut (about $150 more). I'll put all the details on the Forum as I get them. Gear Vendors has sub-contractors who will do the whole job for $750, and Camping World will do the install for $600. The folks at GV told me many back yard mechanics do the install themselves, and just get the shaft cut done at a shop. I don't have a place large enough to do the work, and I'm a little hesitant about removing and replacing the drive shaft brake. Besides, this neighbor has done these before, and owns his own transmission repair shop. OK, there are the details I have so far.
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Old 06-17-2006, 10:40 AM   #8
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On the subject of optimal RPM, does anyone have a source for the torque and horsepower curves for these engines (esp. the 454). I imagine there is some variability year to year and that other factors (ignition, aspiration, exhaust) could cause variation. Nonetheless, a baseline would be helpful.
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Old 06-17-2006, 12:54 PM   #9
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Before I do the same..........

A few weeks back, I was within a day or two of writing a check for a Gearvendors. I came across a post in this forum asking for opinions on US Gear vs Gearvendors splitters. It is clear that Gearvendors has more of the MH market and that US Gear is "trying harder". The post had in it someone's opinion that Gearvendors was less troublefree than US Gear. The original post in this forum got no replies.

Are there any opinions? My use, like Tim's, is not daily; and I will eventually be pulling something small and as close to the 1 ton limit as I can get.

Rob
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Old 06-17-2006, 07:52 PM   #10
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Originally Posted by guy99
On the subject of optimal RPM, does anyone have a source for the torque and horsepower curves for these engines (esp. the 454). I imagine there is some variability year to year and that other factors (ignition, aspiration, exhaust) could cause variation. Nonetheless, a baseline would be helpful.
Guy99 and Rob,

First, according to a book I have, Rx For Performance and Mileage, published by "Trailer Life" in 1983, written by John Geraghty and Bill Estes, the 454 numbers were peak horsepower 230 @ 3800 rpm, peak torque 360 @ 2800 rpms. (Ford 460 numbers were horsepower 202 @ 4000 rpm, peak torque 331 @ 2200 rpm). Since these numbers didn't change much as long as these engines were carbed, they should be reasonably close for most of the Airstream MoHos. The general advice is to stay somewhat below peak torque when heavy loading, so the Chevy should be running a little below 2800 rpms, and the Ford below 2200 rpms (an impossible task, but the closer the better). Horsepower, of course, doesn't impact moving one of these large heavy vehicles nearly as much, since its major influence is on speed. Torque being the key, it's pretty clear I need to slow my engine down. I can't speak for all the 454 folks, but maybe these figures will at least be a little help.

Second, Rob, I've heard the same things a few times, but I still like the way GV gives you a true extra 3 speeds. Also, GV supplied thousands of their units for many SOB motorhomes as Factory equipment, so they have to be relatively good. Even Chevrolet used them for some of their Corvettes. If major manufacturers have used them successfully, I'd assume they're pretty tough. My tranny guy says they're extremely tough, and he's put many of them in. Obviously, I can't speak from experience, but I haven't found anyone who's used a GV unit tell me not to. I'm sure the US Gear units are good, but GVs provide exactly what I need. More gearing between 1st, 2nd, 3rd, and a true overdrive above 3rd. Ultimately, there is less gap between each shift - making for smoother shifting and less strain - and you're not just adding an underdrive or overdrive with the same spacing as now.
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Old 06-17-2006, 09:37 PM   #11
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Tim,
Thanks.

I have read that peek efficiency (mileage) will occur at the RPM where the torque and horsepower curves cross.

I don't know if this applies only to diesels? Does anyone else?
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Old 06-17-2006, 10:41 PM   #12
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Tim: My conclusions are the same as yours. I am quite prepared to write the check--but it never hurts to check things out.........no pun intended.

I will get this done sometime in July. It will be interesting to compare notes.

Rob
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Old 06-18-2006, 01:18 AM   #13
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Fwiw-

Hello- great exchange of info between you guys- should help others make the step into these fantastic devices.

My own experience is as follows- On INHERITED Gear Vendor, which I had no experience with or understood what it did, but the theory sounded good, I bought a mid 80's F250 in Chula Vista from a good ol' boy/desert rat type guy, for $2K- less than what a GV would cost installed- as I was told.

The 6.9 NON Turbo Diesel, was running well at 160K. It had a C6 and I have no idea what rear end differential ratio.

On the highway, pulling a trailer or not, I rode at 70-75 usually. 75 was a little on the loud side and it felt with the high revs that it was too much. I stayed around 72 for a decent feel, and used the surprisingly still-working Cruise Control.

With the GV overdrive on, I was at 2000 RPM, at that speed, at about 65MPH, I saw around 1850/1900 RPM, and it was a nice easy ride. At 65- if I popped the switch and left the OD into normal range, it immediately jumped to 2400 RPM's and felt like all hell was breaking loose.

I drove the truck, basically trouble free for 40K that year. I had to replace the lift pump, and a couple injectors- nothing serious- those injectors were about $24 each- unlike my PSD's...

When I decided enough was enough and wanted another hauling vehicle- with 4WD, I had my mechanic remove the GV, had to find a new tailshaft for the C6, and have the drive shaft extended back to original. I put it up for sale, and a friend wanted it for his son. I was asking $2500, but took $2000 from him- what I paid, and I had the GV.

I explained- it CAN'T be driven over about 55- he said it was perfect, his son pushed it- drove it around at 70- passed me one day and I saw it myself. Within 2 weeks, he had problems with the valves and lifters from over revving, and there it sits.

I called GV, got the prices for installation parts to use it in my F350PSD, and will eventually throw it in there.

I say you should be throughly satisfied and impressed... I was, especially that it was for free.
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Old 06-18-2006, 11:02 AM   #14
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Originally Posted by millionairstream
Hello- great exchange of info between you guys- should help others make the step into these fantastic devices.

I say you should be throughly satisfied and impressed... I was, especially that it was for free.
Guys,

Thanks so much for the feedback. Of course, short of sending the unit back, I'm now committed to this thing. It's great to know of positive experiences like Millionairstream. I feel good about the choice, especially for my MoHo with such low gearing.

Rob, I'll keep my experiences and pics posted, so I'll be anxious to hear how your experiences go.

Guy99, I haven't heard about peak efficiency being where the horsepower and torque curve meet, but I'm certainly not an expert on this either. Makes sense in theory, but in my case it's impossible to keep the rpms low enough to get them to cross while driving down the highway. Simply too low a gear - causing the rpms to rapidly go past the torque curve. Might be true for the 454s, since most of those had axles in the mid 4 range (i.e. 4.56, etc.). Of course diesels are all about torque anyway. The book I quoted (on performance) is old, but still pertinent to most of our Classics, since our drivetrains are based in the 1980s. They stress the importance of torque over horsepower for pure load moving ability. They also say we should look for vacuum readings between 10 and 12 for maximum fuel economy. My rig runs about that at 50-55, but starts to fall above those speeds. The overdrive should help with that problem.




Thanks again for the helpful comments,
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