ATC 250SX and 250ES Differential Rebuild Tutorial

[Flyingw]

Well that's it. In all, about a 5 hour operation but that's with powder coating. Properly done, this diff will be good for another 25 years assuming the water intrusion issues are kept in check. When you install the differential, each joint should be sealed with sealant. Don't rely on Honda's orings to keep water out. I don't even install the orings anymore. Just a generous amount of sealant does the job. Feel free to post away. I have three more of these to do over the next few days so I'll be busy. I also have an SX to finish for a guy in Tulsa. Enjoy and good luck.

ATC 250 ES/SX Differential Rebuild Tutorial..... Complete

[wonderboy]

Oh my is that completed diff a thing of beauty! Seriously, seeing that thing all pretty on the outside and knowing it is perfect and brand new on the inside makes me happy...

This write-up is just awesome. I hope some day to do a write up 1/2 as good as this one. Thanks!

[trike savior]

awesome write up flyingw. you do some good work.

you had it easy LOL. I know you have done work for UPNATM and don't know if he ever told you, but I did the diff for his first bike. he said it had been apart for 25 years and he had lost one of the ring gear shims. took some work with dial gauge and some plasti gauge but I got it figured out. I had never seen it happen before, but one of the balls on the pinion bearing was actually dented. not like there was a chunk broke and missing, but actually looked dented. don't know how that happens to a solid steel ball but interesting none the less.

this write up will help a lot of people. awesome work.

[Dirtcrasher]

Excellent write up Jim!!

One thing I should mention. As water intrudes the axle and the drive shaft gets pitted; I would check with Harwal (who I use; They may be in Vermont with rubber coated seals.....) especially in the East coast for a seal with 1 or more probable, a 2mm smaller ID. Then a person can toss it in a lathe and remove .040 or .080 roughly to have a nice new surface for that pinion seal to run on.

And all you guys running shaft drives, check that diff oil often, make sure it's clean and that the breather hose is nice and high!!

[DohcBikes]

Thanks for a great writeup Flyingw! I was just wondering the other day how critical the backlash was on shaft driven trikes....great to get trusted input from a pro such as yourself.

[Dirtcrasher]

Thanks for a great writeup Flyingw! I was just wondering the other day how critical the backlash was on shaft driven trikes....great to get trusted input from a pro such as yourself.

It's that wear pattern that's so important. Some people even LOSE the shims and make it work, but severely ruins it's longevity. Honda has a bunch of part numbers for various shims. No, it isn't a Ford 9" or a Dana 60, but, it's just as important and if you start from scratch, you have to put blue marking on the ring and pinion and get it correct.

Again, IMHO, the biggest issue is water intrusion. And, if caught in time, your fine. But the people that neglect it and just keep playing in the mud and water that lose the gears themselves within time...........

[Flyingw]

DC, if I had it my way. I would have the sealing surfaces of the ring gear hub and propeller shaft reconditioned however, the ring gear hub and differential end of the propeller shafts are plated with a very thin layer of hard chrome. The hard chrome provides a durable long lasting finish suitable for sealing. This means those areas can not be machined without destroying the hard chrome. Thanks to the EPA, shops that used to provide hard chrome finishing are extremely hard to find and the ones that do hard chrome charge out of this world rates mainly because the cost of the process and maintaining the EPA license. Hard chrome is used in things like hydraulic actuator pistons, aircraft landing gear struts and so on. With all that said, all we can do is clean off the corrosion and reassemble with the hopes of getting an fluid tight seal.

Dohc, the backlash is very critical with any meshed gear assembly. The right angle (hypoid) type gear sets will prematurely wear the gears if the backlash is too tight and will destroy the gear teeth if the backlash is too loose so yes, the correct backlash is essential.

[Flyingw]

Prussian Blue is what is typically used to check the contact patterns on gear sets and as you said, Honda does have part numbers for different shims but that can get a little expensive. The procedures in the book are written basically for installing a new gear set and since each new mated gear set is different then having an assortment of shims would be required but for this exercise, reinstalling the same shims will usually preserve the shimming that was done when the differential was originally assembled assuming the differential has never been messed with. I took apart one differential a couple years ago. Someone had removed the ring gear and failed to install either of the shims. I tossed the whole thing in the trash. The teeth were completely destroyed.

[atc007]

As someone who's done more of these than I can remember. A+++++. Mine were mechanically sound. But they darn sure weren't these true works of art!! I don't have a blast cabinet,,,,,yet. Your work is next level all the way Jim. THREE days guys,,THREE days it took him to do this. THANK YOU sir. I was gonna say to about using a NEW vent hose,and routing it right up to the steering stem under the tank,but DC beat me to it. Without that,,water intrusion,and off we go. Also, I have seen two? or more of these Pop the side of the case right out at the pinion bearing,,not from a rock,,from so much garbage and metal grinding around in that small area. I will try and post pics sometime.. Just don't hold your breathe,,I may have junked all of them..This HAS to be moved up as a sticky!!!! WITH his carb tutorials!

[Flyingw]

I totally agree on the vent hose although on my SX, I put a short piece of hose and screwed a valve stem cap on it with a tiny breather hole in it. It will let air out but I don't swamp my trike but if were to, I'd pull that off and run a hose up.

[dougspcs]

As usual Jim your builds are like a great chick flick!!

Starts out as a love gone bad scene, it's old and broken, the beauty is gone and is there really any hope??

As the plot develops you see things get torn to pieces and worse than ever, surely this is the end of it forever right?..but wait!!!

Suddenly, seemly by accident but yet ever so intentionally it's love reborn, as beautiful, shiny and even stronger than ever!! Awwwww...

Sniff, sniff..

Or at least that is what I've heard!! Chick flicks..blah!!

But nice diff though.., I'll be heading your way with one this spring!!

[Flyingw]

Now that cracks me the hell up!!!!!

[Flyingw]

When you guys replace you rear axle tube bearings here's one thing that will get you in to trouble. When you are ready to assemble the rear end, there is one thing you need to be aware of. Before you do final assembly on the rear end and commit sealant to anything, dry fit everything. You can go ahead and mount the diff in the swingarm with sealant and bolt it down. Where you will encounter a problem is with the long axle tube. The bearings do NOT get driven all the way down. If you look on page 12-11 in the SX manual, you will see they callout a bearing driver. That bearing driver sets the depth of the bearings but they don't tell you what that depth is. If you drive the bearings all the way down, it shifts the axle to the right and prevents the right axle tube from flushing up against the swingarm flange by about 1/8". I drive the left axle tube bearings down to about 10mm from the edge of the axle tube flange. The seal is about 10mm thick. When everything is pulled down tight, it leaves about 2 threads exposed outside of the axle nut. After to dry fit everything, be sure the axle still rotates. If all is good then pull it back apart and seal all the joints and do your final assembly. The right axle tube that's inserted in the back of the brake panel does get its bearings driven all the way down so the snap ring can be inserted.

I have also had a couple of guys ask what sealant I use. Permatex Ultra Black. Let any squeeze out cure. If you wipe off the squeeze out while its wet, it WILL end up smeared all over you, the trike, and anything else you touch. Let it cure and it comes off nice and clean.

[acellr8]

Just wanted to thank Jim for this thread and for all the help on getting my 250ES back on the road. I amazed at the knowledge he has on these machines. Also, just wanted to say thanks for the newly rebuilt rear differential you built me. It is a work of art and truly looks Brand new, almost too nice to put on my trike.

Thanks again for the help and the new diff!! Much appreciated!! As you can tell I am excited it has arrived and can't wait to get it back together.

Regards,
Ed Rist

[Flyingw]

You guys are welcome. Let me know how it works when you get it installed.