Underdrive question-no don't want to run it backwards

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Deere boy
Posts: 8
Joined: September 10th, 2018, 12:21 pm
Body Type: truck
Model Year: 1928

Underdrive question-no don't want to run it backwards

Post by Deere boy » September 20th, 2018, 6:55 am

I am building a speedster/rat rod type of thing using as many tractor parts as possible. The transmission is a three speed model A and the rear end is also model A car. In my first test drive, I had a problem I never planned on, it is too fast in low gear. I need to be able to putt around at shows at five miles per hour or so, but it wants to run about twice that.
I seem to have two choices, replace the three speed with a four from an AA or add an underdrive.

Adding the four speed provides a new set of problems. I am not using the A bell housing so I can't switch it to the shallower AA one. I would also have to change the adapter plate I have now because a three speed bolts on with four bolts and a 4 speed with six. If I bolted it to where the three speed is now, I'd have to shorten the drive train by 3 inches.

My other choice would be to add an underdrive, it should bolt to the back of the three speed without problem, but again the drive shaft would have to be shortened. If I found someone to graft the underdrive into the drive shaft and torque tube, would it be a problem for it to run at an angle?

P.S. Installing 4.11 gears in the rear end wouldn't slow it down enough.

KimVanOrder
Posts: 469
Joined: August 11th, 2013, 4:25 pm
Body Type: 82-A Platform
Model Year: 1928
Location: Hamilton, Mich.

Re: Underdrive question-no don't want to run it backwards

Post by KimVanOrder » September 20th, 2018, 8:37 am

Or, put two three speeds in line. Dad in law built a go cart for his daughters that way. Gives lots of options.. Cheep and easy.
KVO
Dec. '28 AA

Deere boy
Posts: 8
Joined: September 10th, 2018, 12:21 pm
Body Type: truck
Model Year: 1928

Re: Underdrive question-no don't want to run it backwards

Post by Deere boy » September 20th, 2018, 9:18 am

While that may be true and is something to consider, in order to graft it into the drive shaft there would have to be machining on both ends. I believe an AA underdrive would bolt up to the three speed.

KimVanOrder
Posts: 469
Joined: August 11th, 2013, 4:25 pm
Body Type: 82-A Platform
Model Year: 1928
Location: Hamilton, Mich.

Re: Underdrive question-no don't want to run it backwards

Post by KimVanOrder » September 20th, 2018, 4:38 pm

Or !! Switch to the low speed worm drive rear end. 7:25 to 1, and then add a Utillity TT over under drive at the rear end. The standard under drive for an AA is the way to go. I have a three speed, with under drive and low speed worm. Parade walking speed is , 2nd gear, in under drive and medium idle. I have the Utillity TT under/over drive unit under the bench is your interested. May all so look cool to put on really small dia. tires. 12"or 13"...
KVO
Dec. '28 AA

Deere boy
Posts: 8
Joined: September 10th, 2018, 12:21 pm
Body Type: truck
Model Year: 1928

Re: Underdrive question-no don't want to run it backwards

Post by Deere boy » September 21st, 2018, 6:52 am

KimVanOrder wrote:
September 20th, 2018, 4:38 pm
Or !! Switch to the low speed worm drive rear end. 7:25 to 1, and then add a Utillity TT over under drive at the rear end. The standard under drive for an AA is the way to go. I have a three speed, with under drive and low speed worm. Parade walking speed is , 2nd gear, in under drive and medium idle. I have the Utillity TT under/over drive unit under the bench is your interested. May all so look cool to put on really small dia. tires. 12"or 13"...
Changing the rear axle would also entail different wheels, springs and I believe still machining the drive shaft.

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