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Old 04-03-2006, 08:36 AM   #1
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1975 26' Argosy 26
London , Ohio
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Question Gear Ratio ?

I would like to know what the differantial(rear end) gear ratio is in a couple Argosy motorhomes. The frist is a 1975 26foot with 16 inch tires and the second is a 1977 28 footer with the 19.5 tires. Doing a little day dreaming and need more information. hope some body can help me.
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Old 04-07-2006, 10:04 PM   #2
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1960 24' Tradewind
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hello Slow -canoe,

the only real way to tell the ratio of your motorhomes is 1st get the vin# vehical ID off the registration . call the gm dodge or ford dealer whichever these coaches are and give them the vin# POSSIBLY they can tell you what your ratio is . Usually that series of numbers and letters represent options axles brakes and such . But not always . ON gm chassis there may be a build sheet glued to the underside of the hood (van type) it will have a code for each ordered item?option for that vehical . 2nd way is to get under coach and look for a little tag bolted to the rear diff cover . On dana axles it will tell the ratio such as 4:10 or? ford may have a tag . Gm no . 3rd and unpleasant way is to get the rear cover removed drain oil , there will be numbers on the ring gear (the large gear) edge say 41 10 or 39 12 this is best left to you if you can or have done this or a auto truck rv repair shop. The numbers may not be where you can see them without rotating the gears ,hence raising vehical rear off ground to rotate ring gear.the 4th way i wont advise to dangerouse so forget it .Now all that being said whew, the 16 inch would have should have 4:10 ratio if GM. DANA axle ford could be 4:09 The 19.5 which is gm could be say in the 6:17 range a common truck ratio . I surmize that the smaller coach is also GM. I know the truck chassis better than argosys. I suggest if you want more top gear or better mileage go with a gear vendors over?under drive setup . Extra low gear and extra high gear they are great . Most bigger rv outlets should be capable of performing this modification. Most all rvs and trucks will use the lowest ratio within reason to get the weight moving so its a compromise . gear vendors solves or rather improves this compromise.

Good luck

Scott of scottanlily
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Old 04-07-2006, 10:10 PM   #3
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axle ratio

Probably it is a 4:56
You can easily tell by putting a chalk mark on a rear tire, say at the bottom, and a chalk mark on the drive shaft where you can observe it easily while it is slowly turning.
Then have a helper drive it, either foreward or backward one revolution of the tire, while you count the revolutions of the drive shaft.
if it turns say just a tad over 4 turns you have a 4:11 or if 4-1/2 turns it is a 4:56 .
You might have to lay down alongside of the coach while it is S-L-O-W-E-L-Y moved, but it is a sure easy way to tell.
The other way is if the cover is removed from the differential for oil change or service, count the teeth on the ring gear and divide it by the number of teeth on the pinion gear.
most Numbers are stamped on the ring gear and/or pinion like 10-37 ( 3:70)
or say 9-41 (4:56)
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Old 04-08-2006, 05:12 PM   #4
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Quote:
Originally Posted by George
Probably it is a 4:56
You can easily tell by putting a chalk mark on a rear tire, say at the bottom, and a chalk mark on the drive shaft where you can observe it easily while it is slowly turning.
Then have a helper drive it, either foreward or backward one revolution of the tire, while you count the revolutions of the drive shaft.
if it turns say just a tad over 4 turns you have a 4:11 or if 4-1/2 turns it is a 4:56 .
You might have to lay down alongside of the coach while it is S-L-O-W-E-L-Y moved, but it is a sure easy way to tell.
The other way is if the cover is removed from the differential for oil change or service, count the teeth on the ring gear and divide it by the number of teeth on the pinion gear.
most Numbers are stamped on the ring gear and/or pinion like 10-37 ( 3:70)
or say 9-41 (4:56)
George is absolutely right that is the quickest, and I would agree easiest way to get the ratio - at least very close to it. Of course, you may have a tag like I do on the differential. Unfortunately, I have a 370 with a 5.29 , so I can climb mountains pretty well, and do well around town. The highway speeds above about 55 cause too much rpm. I'm investing in a Gear Vendors over/under drive right after I get back from a short camping trip next week .
Sorry - that's off the subject, but seriously, many axles have the ratio on a tag. You just have to get under there an look around real well. George's solution is simplest, I believe.

Best,
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Old 04-09-2006, 02:08 AM   #5
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WEll , yes that was the 4th idea I was going to suggest . I did not feel comfortable telling someone to lie down on the ground and look at the driveline next to a moving motorhome even if it is moving slow . The chalk mark idea is how I do it if there is no tag. People get hurt all the time doing seemingly simple tasks .If you dont feel comfortable trying to do this procedure (yes its is simple) your local mechanic could check it for you.
If you pull the cover to look ,you cant count all the ring gear teeth unless you turn the ring gear ,how would you see the teeth you cant see when looking at it? No way can you count the pinion teeth . If you are lucky and the ring gear is in the right spot the ratio numbers are stamped on the ring gear edge like 10 37 or 9 41 then divide the # to get the ratio as george has stated .Sometimes there is a tag just get under and see .It wont be a 4:56 with a 19.5 tire has to be a lower ratio .The common 1 ton GM rear axle is the corporate 14 bolt with 16" wheels in the year 1975 could be a 4:56 ,it would rev high at 65 . Probably 4:10 .The rear axle in the other coach in 1977 would be a corporate GM with 19.5 tires .With that size of rim and tire combo you need a much lower ratio to move the load. Would be in the 5:29 ratio . As I remember it there were 4 gear ratios available for the axle with 19.5 tires. 5:43 was the tallest gear mine had a 6:17 ,really reved at 65 mph.
By the way in my previouse post I did suggest to pull the diff cover to identify the ratio . I dont understand why george suggested the same procedure in his post almost exactly , since it came up right after mine.

anyway slowcanoe

Good luck Scott

Scott of scottanlily
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Old 04-09-2006, 11:21 AM   #6
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Quote:
Originally Posted by scottanlily
WEll , yes that was the 4th idea I was going to suggest . I did not feel comfortable telling someone to lie down on the ground and look at the driveline next to a moving motorhome even if it is moving slow . The chalk mark idea is how I do it if there is no tag. People get hurt all the time doing seemingly simple tasks .If you dont feel comfortable trying to do this procedure (yes its is simple) your local mechanic could check it for you.
If you pull the cover to look ,you cant count all the ring gear teeth unless you turn the ring gear ,how would you see the teeth you cant see when looking at it? No way can you count the pinion teeth . If you are lucky and the ring gear is in the right spot the ratio numbers are stamped on the ring gear edge like 10 37 or 9 41 then divide the # to get the ratio as george has stated .Sometimes there is a tag just get under and see .It wont be a 4:56 with a 19.5 tire has to be a lower ratio .The common 1 ton GM rear axle is the corporate 14 bolt with 16" wheels in the year 1975 could be a 4:56 ,it would rev high at 65 . Probably 4:10 .The rear axle in the other coach in 1977 would be a corporate GM with 19.5 tires .With that size of rim and tire combo you need a much lower ratio to move the load. Would be in the 5:29 ratio . As I remember it there were 4 gear ratios available for the axle with 19.5 tires. 5:43 was the tallest gear mine had a 6:17 ,really reved at 65 mph.
By the way in my previouse post I did suggest to pull the diff cover to identify the ratio . I dont understand why george suggested the same procedure in his post almost exactly , since it came up right after mine.

anyway slowcanoe

Good luck Scott

Scott of scottanlily
Scott,

I certainly didn't mean to suggest that one just carelessly lie on the ground while another person drives the coach forward. Safety has to be the first consideration, and people do get hurt doing simple things all the time. Done correctly (i.e. safely), however, one can get a good read on axle ratio with the chalk method.

Maybe George was composing his answer and hadn't seen yours before he posted. I've had that happen to me several times. Ends up making one look like he's not paying attention, when he actually was trying to help.

Maybe Slow-canoe will get real lucky and have a tag on his differential.

Best,
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Old 04-09-2006, 08:59 PM   #7
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Hay everybody don't get a excited ,I just was looking for information . I am have found two motorhomes to look at . The plan is to transplant a diesel and as you know they do not like rpm. One thought is to use a Allison 4 speed with 3.73 gears if I go with the 26 foot Argosy , but like I said the 28foot Argosy has 19.5 tires and I was just not sure, In my opinion the 28footer would have no more than 4.56 or outside 4.88 gears . Now my math says that SCOOTANLILY 's 6.17 gear would turn the 454, 4100RPM at 65 MPH . A steady diet of that would be the death of it. Now the Allison trans mission has 3.45 frist gear, 2.25 second gear ,1.41 third gear and 1-1 high gear should get it up and going and rely on the 3.73 or 4.10 for the highway. going this route looks cheaper and stonger than a GV overdrive. Wanting to keep rpm 25-2800 at 65-70 mph. As far as the trans and the gears I can do the work my self. (It will pay about like a lot of other work I do) but it sounds like a fun project. As far as what gear is in something first the vin and the GVW tag , second the tag on the rear cover or remove cover(if it has one) some list the ratio,compare part number or count ring gear and pinion gear teeth and divide pinion teeth in ring gear teeth. As far as the chalk on the drive shaft will only get you close.
But hay everbody thanks for your help!
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Old 04-10-2006, 06:51 PM   #8
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Hey Tim ,

Thanks for the clarification on the posting with regard to georges posting . Im sure you are correct and no offence intended to george I just didnt understand why that would be and now you have cleared it up for me . I have found that some posts come up twice or once in a seemingly different spot . So I understand my mistake .Further more as seen his information was spot on . As a note , the 6:17 ratio would rev the life out of the 454, yes and the tire size would definatly have to be a tall . Probably is the taller gear like the 5:43 , much lower rpm at 65 .The allison is the best automatic to use ,very heavy duty they can take it.

Scott of scottanlily
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Old 04-10-2006, 08:08 PM   #9
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Fords will have a tag attached to a mounting bolt on the rear axle carrier with the ratio, and GM's will have the ratio stamped in top of the right side axle tube. The two motorhomes you are looking at should have GM drivetrains, so check for a series of numbers stamped on the tube.
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Old 04-10-2006, 09:29 PM   #10
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Thanks I did not know that GM stamped rear end information on the axle tubes, something to remember . Thanks for all the help.
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