What kind of motor need in PMD reduction 4:1 ?

[CarZep]

Need help! I install a
PMD AD-to-Transmission Reduction 4:1 with a tamiya motor 33T but when I run the truck in 1gear and 2gear it makes to much noise in transmission and runs very slow. Can someone tell me what is causing this noise If it is the motor or the PMD reduction 4:1 ?

Sorry for my English, my writing its not to good, I live in Mexico.
Thank you

[mavrick0]

Most people that run the GRU just run the stock motor. If it's only making noise in 1st and 2nd then I'd say it's in the tranny. Make sure your servo is shifting the tranny properly and not over or under shifting and making the gears jump. Also another thing I've seen a lot is the pinion on the motor isn't sitting right and the little set screw actually rubs on the spur gear and causes some noise as well.

[ricm]

Need help! I install a
PMD AD-to-Transmission Reduction 4:1 with a tamiya motor 33T but when I run the truck in 1gear and 2gear it makes to much noise in transmission and runs very slow. Can someone tell me what is causing this noise If it is the motor or the PMD reduction 4:1 ?

Sorry for my English, my writing its not to good, I live in Mexico.
Thank you

I've got the same set-up in my King Hauler....Tamiya's Torque Tuned 33T truck motor with PMD 4:1 reduction. The reduction gearbox has steel gears, so it does make a bit of noise. But this should be the same in any gear.....maverick0 is correct to suggest that you check:

1) the transmission shift servo is set up correctly - this is the cause of MANY mechanical problems in Tamiya trucks. If the gear is not fully engaged then the dog teeth jump, sounds like a grinding noise. In 2nd gear, the servo should be in middle position....1st and 3rd gear should have the same amount of servo movement in each direction from 2nd, so that the circlips on the shift rod -just- touch the gear casing. Too much more, and the servo will bind and get damaged in the longer term
2) position of pinion on the motor shaft (if the pinion is too far from the motor then the grub screw will chew into the nylon gear it drives, making noise and damaging the gear).

Also, check:
3) there is some clearance between the teeth of the motor pinion and the drive gear. Easiest way is to set the motor position with a piece of paper between the teeth. When you remove the paper, the clearance should be about right
4) the grub screws for the drive axle cup joints are tight (use the threadlock!)
5) axles are running freely
6) the inside of the rear wheel rims are not rubbing on any of the suspension parts

but with everything set up right, the truck does run very slowly in 1st (which is the whole point!), and it a bit more noisy than a standard build because of the steel gears...

[Cooper]

I also had to tear one apart because of the pinion set screw catching. When I would run the truck slow it would surg slightly and when fast it had a bad vibration, all caused by set screw catching. Just thought I would say that if it helps.

[CarZep]

Thank you my friends for your help you where right the problem was the pinion.

I have another doubt, what motor would you recommend to put in an Integy 65t or Tamiya 33t? I am also putting a 4:1 reduction PMD. Thank you again

[bigford]

I'm slow enough with my 65t motors with no gru.you would be
even slower but have more pulling power. rc4wd motor are $10.00
on ebay you can try the 55,65,80t for $30.00

[fhhhstix]

Thank you my friends for your help you where right the problem was the pinion.

I have another doubt, what motor would you recommend to put in an Integy 65t or Tamiya 33t? I am also putting a 4:1 reduction PMD. Thank you again

I use a 55 turn and a 4:1 or 3:1 in all of my trucks. I tried using higher turn motors and smaller pinions but I just wasn't happy with it. A 4:1 after the trans and a 55 turn will give you a lot of power but still have more than enough speed especially while at a show with other trucks

[Mustang46555]

I've ran the stock Tamiya kit motor with a PMD 4:1 in my Knight Hauler for over five years now. My 4:1 is the earlier separate unit rather than the new bolt on but the ratio is the same. It has plenty of power, pulled Rick's big drop deck all over Indy one year with Willy steering the rear of the trailer. Truck never broke a sweat, even when we went outside and cranked her up into 3rd gear with Lynn's quarry dumper as cargo! Driving with a normal trailer is nice and smooth. Very controllable in a crowded environment. I'd assemble it with the reduction unit and the stock motor first and see how you like it.