1986 DT75 Drive shaft stuck to the pinion gear

[NothingEverWorks]

Today we we're trying to replace a gear in the gearbox of the engine. The drive shaft lower end nut was really tight, but after several tricks we finally managed to remove it. However the drive shaft is not coming off. I suspect that the nut has been tightened too hard last time and because the junction is cone shaped, the pinion gear is stuck to the drive shaft. It's not possible to use a puller to remove the pinion gear due to lack of space on the lower end of the drive shaft and there is nothing to grab on the higher end of the shaft. The top side of the drive shaft has been disassembled to the point that there is nothing more to be removed. Hitting under the drive shaft didn't work yet. The drive shaft does move maybe a couple of millimeters up and down.
Any ideas on removing the gear? Or is there something else that's keeping the drive shaft or the pinion gear in place?

[Solarman]

You said you removed everything up top. You removed the water pump assy? And under that is the bearing cap that holds the driveshaft down in place. If you've removed the nut on the bottom of the driveshaft it should slide out of the pinion gear. Once the bearing and cap are off there may be enough room to slide a piece of plastic pipe down the driveshaft to the pinion gear to gently nudge the pinion gear while pulling the driveshaft up?

I've not worked on the dt75 gear box, but do remember each spacer/shim/washer is critically important to put back exactly where they came off.

Good luck, post back on what you find out.

[tjdarst3]

I’m experiencing the same problem on my ‘87 DT75. Also, where did you find your replacement gears?? I have been looking all over the web with no success.

[NothingEverWorks]

I got my hands on a spare engine of the same model. Turns out that the drive shaft of the original engine has been twisted in an accident involving an underwater rock. When disassembling the spare engine the pinion gear fell off easily as it should. I think the next step might be Solarman's plan of putting something in between the drive shaft and the pipe it's in. I'm afraid that we might have to forget about the gentle part though. I'll post the results.

[redlowrey]

I got my hands on a spare engine of the same model. Turns out that the drive shaft of the original engine has been twisted in an accident involving an underwater rock. When disassembling the spare engine the pinion gear fell off easily as it should. I think the next step might be Solarman's plan of putting something in between the drive shaft and the pipe it's in. I'm afraid that we might have to forget about the gentle part though. I'll post the results.

How is that going to work, the drive shaft goes through two bearings that are pressed into the drive shaft housing then protrude through the bottom where the pinion gear is. Seeing you have no equipment, cut a piece of inch by inch and a half piece of wood three inches long and sit it into the housing, then measure between the piece of wood and the bottom of the drive shaft, get a bolt half inch nf, or nc does not mater and cut it so it fits close to the bottom of the shaft and make sure there is at least half inch of thread on it and screw a nut flush with the bottom of the bolt.

Fit a ring spanner on the bolt assembly and fit it between the block of wood with a fifty cent coin on the wood for support and the bottom of the drive shaft, pointy the bolt head towards the drive shaft use an other spanner to hold the bolt head and start unscrewing the nut, this will push the drive shaft pinion against he housing and then proceed to push the shaft off the pinion.

As you un screw the nut the pressure will increase on the shaft till it pushes it off, if it still won't budge while the pressure is on, use your butane torch and apply a little bit of heat and it will fall off.

[NothingEverWorks]

Oh yes I forgot to update on this. The pinion gear was just really tight and luckily not twisted at all. Redlowrey's idea was the one that worked just not completely like that. I had to buy the biggest bolt that I could fit in the chamber and used extension nut as well. No need for blowtorch though. I did try this with the wood block thing too. The space was really tight and the nut had to be turned like 1/12 spins at a time. So any extra moving parts were too much to handle.

Thanks for the advice! Next it's probably time to see if I can still put everything back together as the project has taken longer than expected and absolutely no pictures we're taken at any point.