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Allis 917H engine swap = driveline vibration

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Well, I have the conversion complete on the MV18, and have it running as a horizontal shaft and installed in my 917H. The problem is I have a driveline noise/vibration that I can't figure out. I checked all the shrouding on the engine first, thinking maybe something was loose, but found nothing. Last night I disconnected the drive shaft to the BGB, and it went away. I bolted the drive shaft back up, and the noise/vibration was back. It sounds like it's coming from the engine end rather than the BGB end. I can't think of what might be loose on the engine. I torqued the flywheel, I'm condifent that the bolts for the drive shaft mount are tight in the flywheel. Does anyone have any suggestions on what to look for?

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DMedal
driveshaft bolts all the same length? same # of washers and spacers on each? Try running it with the fiber disk attached to the engine but without the shaft attachment to the fiber disk. "something loose" is where you notice the vibration. unless that something loose is allowing contact the actual source is elsewhere, in an out of balance or out of alignment situation. you're so close! good luck.

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Al
Hi. Is the center line of the crankshaft the same height as the old engine was? If the drive shaft is on a different plane, the couplings could have more flex. If the input shaft on the BGB is worn and loose, as is common, and the alignment is slightly different, it might show up when it didn't on the original engine. Are the mounting pads on the engine exactly parallel with the crankshaft. I am asking as I from memory visualize mounting pads cast in the back of a vertical shaft block. Not making any predictions, just sharing the thought process I would look at. Al Eden

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HubbardRA
Make sure the crankshaft of the engine sits parallel to the shaft on the BGB. "NEVER" try to angle the engine toward the BGB because of a difference in height. If there is "any" difference in the centerline of the engine versus the BGB, the flex disc on the engine will put a pulsation into the driveshaft and then the one on the BGB will remove it. If the shafts do not sit parallel in both directions, the rear disc cannot completely remove the vibration. In other words the angles with respect to the driveshaft must be exactly the same but in opposite directions to neutralize the driveshaft vibration.

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country
The heights and alignments are good, as this Kohler Magnum MV18 block is essentially the same as the KT or horizontal Magnum. I had the old KT that I robbed the oil pickup parts from and the MV18 sitting side by side on my work bench, and all aspects are the same. I checked all the bolts last night, except for the flywheel nut and the four bolts attaching the drive shaft mount to the flywheel. I have not checked the BGB input shaft for movement thought. I hope that's not the issue. This was my winter project just to swap engines, and it's almost August. If I have to take the BGB out to repair it, it could take me 2 years.

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country
All, I forgot to mention it isn't constant, but seems to be at certain rpms. It's not noticable at idle, then picks up through midrange, and seems to diminish slightly at higher rpms.

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HubbardRA
Loosen the set screws in the yoke on the BGB and let it slide if it wants, then re-tighten. When the driveshaft is bolted up, you do not want any tension to put un-needed bends in the flexdisks.

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country
I checked the BGB as best I could tonight. The backlash doesn't seem unreasonable, and there is probably 1/32" of side to side play in the input shaft. That seems possibly a little much, but not severe yet. I'll try Rod's suggestion to loosen the set screws on the yoke and let it slide around and position where it wants to. Hopefully that will solve the problem.

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country
Well, I worked on this again today. I disconnected everything from the BGB yoke up to and including the drive shaft mount on the flywheel. I thoroughly cleaned the BGB input shaft and the ID of the yoke so the yoke could slide freely and easily on the shaft for reassembly. I checked the torque on the flywheel nut, and it was fine. I then thoroughly sanded and cleaned all mating surfaces and reassembled to make sure there was no debris between any parts. I reinstalled the yoke without the set screw. I installed the fiber disc to the yoke and drive shaft. I pulled the spark plugs and turned the engine over a couple of times to give the yoke a chance to settle in where it wanted and installed the set screw. The vibration has decreased, but is still not gone. It's still only at certain rpm's, in the lower to middle range. It becomes much worse under load. I kept driving it around with different rpm, and it goes away at higher rpm, where you would be mowing. Any more suggestions or thoughts on what to check? I want to start using it, and I’m thinking about going ahead and mowing since it will be at high rpm where I don’t notice the vibration.

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