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-   -   Rocky mountain under drive ? what is it ? (https://www.fordbarn.com/forum/showthread.php?t=283564)

31Abone 07-03-2020 09:18 PM
Rocky mountain under drive ? what is it ?
 

3 Attachment(s)
A "T" man here said it was not Model T or model A ? anyone know what it is ?

chrs1961815 07-04-2020 04:32 AM
Re: Rocky mountain under drive ? what is it ?
 

The guy was sort of right. That actually was made for a TT truck - read this thread.
http://www.mtfca.com/discus/messages...tml?1231914641

31Abone 07-04-2020 10:21 AM
Re: Rocky mountain under drive ? what is it ?
 

1 Attachment(s)
Great info..should have posted to T forum..pic that i found on search

rotorwrench 07-04-2020 10:49 AM
Re: Rocky mountain under drive ? what is it ?
 

Most of these type units function and a two speed rear axle would. Some are under drives to allow for lower gearing ratios for pulling heavy loads. Some units like this are both an under drive and an over drive for a three way split of gears giving nine possible speeds forward and three in reverse.

Since that one is advertised as a six speed then I'd be relatively certain that it is just an under drive box with an under drive ratio and a one to one ratio only. This way a person can split shift in all three forward gears giving 6 ratios usable in forward motion and two ratios in reverse.

Units were manufactured to work with the Model AA trucks as well.

Bob C 07-04-2020 11:04 AM
Re: Rocky mountain under drive ? what is it ?
 

Quote:
Originally Posted by rotorwrench (Post 1905920)
Most of these type units function and a two speed rear axle would. Some are under drives to allow for lower gearing ratios for pulling heavy loads. Some units like this are both an under drive and an over drive for a three way split of gears giving nine possible speeds forward and three in reverse.

Since that one is advertised as a six speed then I'd be relatively certain that it is just an under drive box with an under drive ratio and a one to one ratio only. This way a person can split shift in all three forward gears giving 6 ratios usable in forward motion and two ratios in reverse.

Units were manufactured to work with the Model AA trucks as well.

The Model T only had a two speed transmission so the Rocky Mountain
would have to be a three speed to get six speeds. The ad shows
three speeds in reverse.

31Abone 07-04-2020 11:15 AM
Re: Rocky mountain under drive ? what is it ?
 

1 Attachment(s)
more info picture

rotorwrench 07-05-2020 11:25 AM
Re: Rocky mountain under drive ? what is it ?
 

Quote:
Originally Posted by Bob C (Post 1905924)
The Model T only had a two speed transmission so the Rocky Mountain
would have to be a three speed to get six speeds. The ad shows
three speeds in reverse.
Your right. It's an over under then. I keep thinking about my Grandad's old IHC Six Speed Specials. He never had Model TT trucks.


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