Overdrive

I think Mack sells them still. Don't seem too expensive.

Hey Mack . Yes I'm interested in a gearbox . Need to get a 190 to the 180 ratio 22:7/1 . Need asap. Thanks mark, can be reached at 716-866-2114 anytime.

A stock 3rd gear pair is 23 on the bottom and 27 on the top. What you have is slower than a stock 3rd gear when using the stock input gears. The final ratio with an overdrive would depend on what the tooth counts are in the over drive gear sets.

With the stock 19/35 input gears and a 190 - 200 driveline it's 37.08:1. With D 19 final drives I get 34.07:1 and with a 180 - 185 finals I get 30.34:1 It's 25% slower than direct drive which is less than what a stock 7th gear would be.

Just think about it: You have 19 driving 35 on the input gear pair. So, to get the equivalent of direct drive you would have to have 35 driving 19 for the 3rd gear pair. I've said this before, with stock input gears it's not possible to get close to direct. you must speed up the input pair or go to an overdrive gearbox ahead of the transmission.

Edited by O.P.S. Heads - 12 Jun 2016 at 10:09pm

The last two transmissions I built had 1:1 input gears. I like the 1:1 ratio because the 2nd and 3rd gear countershaft gears don't have to be so big in diameter. This is especially nice for the 190 transmission housing as it has a floor in it that has be removed if the countershaft gears are too large in diameter. Yes you do have to make the input shaft and the input driver gear separated pieces. It can be done and they hold up just fine. One has been in use in a pretty good tractor for 10 years with no issues. The gear goes in the transmission first and the input shaft is splined to fit the gear which is installed later.

So, if you have the 1:1 input ratio, build a 24 tooth driver and a 26 tooth driven for the 2nd gear spot and build a 26 tooth drive and a 24 tooth driven for the 3rd gear spot you have three gears with about an 8.5 - 9.0% split between them. 2nd is slightly slower than direct and third is slightly faster. THEN, you use an overdrive gearbox ahead of the transmission to get the correct ratio so that direct drive is your primary gear that is used 75% of the time. All three gears can be sped up as needed by changing the overdrive gear ratio which is much easier than changing the transmission gears.

The ultimate option would be to send your torque housing to Pro Fab and have them build a custom gear box that fits within the torque housing. Quick change gears that are easily accessed and a virtually indestructible piece to work with. Wait about two years and pay the $8000.00 - $10,000.00 bill and you will have one.

If I were going to build a LLSS ever again I would use a model 7000 tractor. The torque housing is a little larger which might make this Pro Fab idea easier. Not to mention there is a ton of room under the hood.