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Martin D

Positive Drive update?

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04-07-2001 10:42:01

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Martin, Thanks for confirming my guess work. I tried the drill trick this morning. Didn't work. Possibly did not have drill spinning fast enough? Should I also be appling some pressure against the drive gear to help it back to the "rest" (engine running) position?

I disreguarded your caution as to how hard it is to disassemble. Had to look around the shop floor for 45 min to find the one of the two springs (from the spring/plunger assembly in the internal holes)! Very small spring - big shop!!

I could not figure out a way to assemble, in which to allow the plunger to move passed the machined ridge which holds the drive out and engaged with the flywheel. The drive is reassembled, but I'm right back were I started. I can see how they are assembled at the factory ( plunger and spring installed from the outside thru drilled holes and then the plug installed on top of them ( I couldn't move the plug up or down in the hole -must be press fit)) Did you get drive disengaged by spinning with the drill or by disassembly? If disassembly what trick did you use to allow the plungers to pass over the ridge?

I also assume - if I were to just assemble my engine/flywheel and starter with the drive engaged. The first time the engine started, the drive should retract like it is designed to. However I am not that trusting. If it doesn't - it means breaking the engine tranny again! More work!!!

Any advice? pointers? anything?

Without your help I would not even had gotten this far in understanding how it works. Thanks Jim

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Martin D.

04-08-2001 07:34:22

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 Re: Martin D - Positive Drive update? in reply to Jim , 04-07-2001 10:42:01  
I have been away from the computer for a couple of days so I am late getting back to you and you have it all figured out. I ended up doing exactly the same thing as you did except I used strips of plastic cut from a snuff box in place of masking tape. I didn't think a drill would spin it fast enough but I hoped that it would help describe the way the drive works. We have suffered with the old drive for years and I can't wait to try the new one as the old one kicked out everytime the engine would fire even once. As you now know, the PD drive won't retract untill the engine spins it fast enough to centrifugally throw out the little "lock" pins inside. The New Holland partsman was right when he said, "don't fool around with that!' He was just a bit too late and I spent a lot of time undoing what I had done in 1/2 a second. So there is a lesson here for those who are going to buy the PD type of drive, do not pull the drive pinion out as it sticks there and is a real pain to get it back in place. It must have to spin really fast to do it that way, and a rebuild shop would use a test stand to do get the rpm up to speed.

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04-07-2001 13:59:22

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 Re: Martin D - Positive Drive update? in reply to Jim , 04-07-2001 10:42:01  

I'm impatient, disassembled the drive again. This time I noticed that when the gear is in the correct retracted position, the ridge (really a valley machined into the inner sleeve was accessable. So this time before assembling collar, sleeve and spring/plungers, I wrapped several layers of masking tape in the valley to the same height as the spiral groves. Then assembled the parts, and with the tape inplace the collar retracted all the way. I then removed the tape and completed assembly of the rest of the drive. Wow, it is finally back to normal and ready for when I put the engine back on.


Positive drive bendix may be great, but beware the innocent when removing or repairing.

Thanks again Martin, if you had not given me the insight to how it works, I may have just quit and bought a new one (45-50$$$)


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04-07-2001 11:31:36

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 Re: Martin D - Positive Drive update? in reply to Jim , 04-07-2001 10:42:01  
On my 55 ford truck I went through the same thing. The guy at the starter shop had a alternater hooked to a test machine with a fan belt and he held the starter on that till it disengaged, most of us dont have a fan belt without a fan. I installed my starter with the drive engaged and started the truck and the starter disengaged. I think the starter on my 641 would interchange with my truck.

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