| Author |
Message |
Hiro Protagonist (205.183.46.161)
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Votes: 0 (Vote!) | | Posted on Friday, February 09, 2001 - 4:18 pm: | |
You guys did a great job with the 8V71 vs. 6V92TA question. Thanks for all the input. Now I have another for ya. Rear-end ratios. What is the meaning in the numbers? 4.1 rear ends, 4.56, 5.12 all these numbers! What do they mean for me? I want to have a bus that can cruise at a nice RPM on the highway at 65+ (cause I want to GET there). But I don't want it bogging down so much on hills I have to creep up them. Someone suggested I get a 4.1 rear-end. Why?
Thanks! |
akrom siddiqi (152.163.205.79)
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Votes: 0 (Vote!) | | Posted on Friday, February 09, 2001 - 10:50 pm: | |
he suggested that cause it is an easy number to remender. |
Chuck (Chuckspeed) (24.108.61.69)
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Votes: 0 (Vote!) | | Posted on Friday, February 09, 2001 - 10:57 pm: | |
Excellent, these are my type of questions. (I'm glad to be back)
The rear end ratio refers to the rotations of the prop shaft (drive shaft) to the rotations of the wheel. (ie 4.56:1)
On more modern coaches 4.56 and 4.88 are common. Now to explain this better in terms of actual speed:
(engine rpm x 60) / (transmission ratio x rear end ratio) / (rotation of specific tire per mile)= your miles per hour.
AN EXAMPLE:
(2100rpm x 60) / (.64 x 4.56) / (489) = 88.2mph For example my friends H3-45 max's out at crusing speeeeeed about 89mph.
Depending on what bus you get, your gearing will probably be slightly lower, and/or you won't want your engine at full tilt all of the time. I personally value speed more than longevity.
The tire specs can be found on most manufactures websites, I can't help on the transmission gear ratios though, other than allisontransmissions.com
Good Luck.
Chuck Speed |
Geoff (206.173.201.174)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2001 - 9:03 am: | |
Since you are looking at the RTS, the best ratio to get is the 4:10. That will give you a top speed of 78 mph and cruising speed of 65-70 without winding your engine all the way out. Incidently, a used 4:10 ring and pinion set to fit an RTS is virtually impossible to find so you will have to buy new and have it installed. If you have questions about the RTS you should visit this web site and read all the past postings on the bulletin boards listed:
http://www.gowheels.com/rts/ |
Mike Eades (Mike4905) (207.190.10.225)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2001 - 7:32 pm: | |
Hiro I sugest you call disney in FL and ask for Vega at VM. Tell him what you havw and if you can buy a used set from Disney. They have about three hundred RTS buses and many parts. I drive for them and have found Vega to be very helpful. Mike |
bob k (216.93.48.226)
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Votes: 0 (Vote!) | | Posted on Sunday, February 11, 2001 - 11:37 pm: | |
Inside the axle housing there are 2 main gears the ring gear and the pinion gear. the pinion gear is attached to the driveshaft, the ring gear is attached to the axle shafts. The gear ratio is just simple math...4.10 ratio would be 41 teeth on the ring gear and 10 teeth on the pinion, a 3.30 ratio = 43 on the ring 13 on the pinion. Thats the reason ratios are offered in oddball numbers, the ring must be divisible by a whole number. |
sam trammell (64.12.103.28)
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Votes: 0 (Vote!) | | Posted on Tuesday, March 20, 2001 - 2:06 am: | |
The reason that the pinion gear does not divide even into the ring gear is so that the wear from a less than perfect gear tooth will be spread among all the gear teeth. |
Wulf P. Ward (63.59.218.233)
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Votes: 0 (Vote!) | | Posted on Tuesday, March 20, 2001 - 8:48 pm: | |
Well, here are my 5 cents. I have worked with the RTS buses for about 7 years. The tallest gear that I have ran across as standard is the 4:58 and the 4:59. It is called the highway gear. The suburban RTS used to have the 4:11 now the tallest gear you can buy is the 4:10. I have a converted 40' RTS bus that I ran for about 25,000 miles over the last 3 years. Here is my experience with the gearing. First off I like to give you the formula for the MPH. It is RPM X 60
divided by rear-end X tire rotation per mile. Like in 2100 RPM X 60 = 126,000 : 4,10 X 485 (12X22.5 tires is 1,988.5) then you have to add 18% for the V-drive 730. that comes to 74.78 MPH. This did not add up for me on the road. I did use 11X24.5 tires and wheels. Using a stop watch at the mile markers I come up with 82 MPH at 2,100 RPM at about 1,650 RPM I was doing about 65 MPH. I like to be at 1,800 RPM for best power but then I am going over 70 MPH. I just came back from Texas and I was using a set of 11X22.5's and they gave me a better RPM range. I think the 4:10 is a little to tall for the RTS. My RTS has a strong 350 HP 6V92, but I can feel a big difference in power from the 5% tire change. My bus was running 74 MPH at 2,100 RPM with my original 4:58 gears and that was fast enough for me. The standard bus gearing (55 MPH times) is a 4:61 and that is 71 MPH at 2,100 RPM. If I had to do it again I would stay with my original 4:58. And that is my advice and I am the Wayward Wulf. I do know RTS buses, but I can't spell worth sh... |
Wulf P. Ward (63.59.218.144)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 21, 2001 - 11:33 am: | |
I was in a hurry last night and I did make some mistakes. # 1. The standard bus gearing is 3:61 and not 4:61. # 2. The final drive in the 730 is based on a final over-drive of 18% and I am not sure if this is part of the 730 being a V-drive.
Anyhow I will use a GPS next time I go for a longer tripp, that will give me the right MPH. |