Alco Diesel locomotive gear ratios

Jack A. Siffert · **Joined:** Mon Aug 23, 2004 5:11 pm **Posts:** 373

Does any know what gear ratios (axle)were used on Alco freight and passenger units? Particularly a Canadian RS-18, A C-420 (American built) Canadian built C-424 and Canadian built FPA-4's
A list of possible combinations for all Road and Road switchers would be helpful.
Any information would be great.
Thanks in Advance.

BSOR Patarak · **Posted:** Mon Oct 08, 2012 8:29 pm

I have a Canadian Pacific MLW built RS-18 and C424 that both have 65:18 gearing and an Alco built C420 with 74:18. It is tough to generalize the gearing, as they may have been ordered differently, or modified by a railroad shop at some point in their life. I'd recommend counting the gear(s) on your units in question....

Pat Connors
BSOR

AlcoC420 · **Joined:** Wed Dec 15, 2010 8:17 pm **Posts:** 270

Alco used several gear ratios. I even know of one railroad that used GE wheel sets with the GE gear ratio.

74/18 65mph
65/18 75mph
64/19 80mph
62/21 92mph
60/23 104mph
58/25 117mph

Most common is the 74/18 ratio.

Jack A. Siffert · **Joined:** Mon Aug 23, 2004 5:11 pm **Posts:** 373

Is the 18 tooth pinion the same size on the 2 different ratios? In other words can you use either axle on the same pinion or did they change the base size and tooth profile for each ratio?

artschwartz · **Posted:** Tue Oct 09, 2012 12:13 am

I suspect that the 74:18 gear ratio has a different pinion than the 65:18 ratio. Otherwise, the armature to axle distance would have to be different, a much more complex manufacturing challenge.

NH0401 · **Posted:** Tue Oct 09, 2012 8:57 am

FPA-4's were geared from the factory for 92 mph top speed.

All the bull and pinion gears used on Alcos were supplied by GE.
They carry a GE P/N in the renewal parts book.

752E8 with 18t pinion are becoming scarce in the RTO market. 74/18 was superceeded by 81/22 ? when the Dash-7's were introduced.

DPK