Big Red Differential to replace 250sx Differential

[cybrman]

Anyone know if there are any differences between the "final drive" differentials of the Big Red 250es and 250sx?
Have a 250sx with a bad pinion shaft bearing, Mr Big Red happens to be a willing "donor". I can't imagine they can be that different if they are different at all as far as gear ratio.

Also another question for you veterans....
Is the main difference between this site and 3wheeler.org East coast - West coast?

Great Site, Can't wait to meet some of you.

[TravEX]

That is a frequent discussion on here, if the gearing differences between the SX and ES are in the transmission or the rear end.

I'm gonna sit back and watch this one play out.

And, WELCOME to 3WW!!!!!!!!!!!! prepare to be addicted.

[Dirtcrasher]

The ES diff I had had a slower top end speed than the SX diff.

[ScottZJ]

Here is a quote from a previous post.

"1985 250es big red has. 9 teeth on the small gear.and 35teeth on the big gear in the diff.the axle is 30"3/8 long. the 1985 250sx has 10 teeth on the small gear.and 34 teeth on the big gear in the diff.the axle is 30"5/8 long."
Also you have to remember the SX has 8" wheels with 22" tires where the big red has 9" wheels with 25" (in most cases hehe).

[hublake]

Here is the gear ratios copy from my manuals. The SX is on the left.

[TravEX]

So, the SX has a 4.96 rearend and the ES a 5.68 rear end? And the tranny gears are quite a bit faster.

So your looking at putting a ES diff on a SX, shouldn't be much different. If you're running 22" knobbies, just add some more air and your top speed should stay the same, hehe.

[cybrman]

Great info guys...thank you very much.
I just managed to get the damn thing off the big red, boy was that fun.
The 2 250sx's were a breeze compared to this old rusted beast. One side of the axle had the nut gauld on it or something (though the threads seemed just fine after removal) so I had to cut it off. Tried to pop the drive shaft back up outta the rear diff and not even close (worth a try) so now its down to the swingarm bolt and the drive housing, couldn't budge either. Frustrated as hell heated swingarm bolt, cleaned it up sprayed with penetrating oil, pounded the heck out of it still won't budge. Heated three bolts on drive housing (allen type) couldn't budge em. Then I turned the beast upside down, pounded each bolt with a hammer three times while chanting "come on ****** ******" and voila they broke loose. I'm guessing I had some better leverage with the trike upside down but I swear the chant helps!

Now for the fun part...the pinion shaft on this diff seems kinda sloppy, not quite as bad but close to the one I'm replacing for what I think is the same reason. UGH.
So far my experience is only these three machines.

1. 250sx #1 Bad one seems like pinion shaft bearing is gone, turns real sloppy to the point that when I tighten up the retaining nut and install it on the bike as soon as it engages in gear it just runs the nut off the pinion shaft and it loses its bite on the pinion gear causing it to spin around the pinion shaft.

2. 250sx #2 Good one on rideable machine now, pinion shaft had very very little slop seemd firm.

3. Big Red Unknown - seemed to work from manually moving axle but not running so I myself have never ridden. Now that its off the bike I see that this pinion shaft seems to turn sloppy too, so I'm inclined to believe it's only a matter of time before this one fails (if it aint already).

Anybody have experience replacing the pinion shaft bearing in these differentials? Seems like it aint too big a deal with the right puller which I of course do not have.

[ScottZJ]

The bearings arent too bad to replace except the main pinion spindle bearing. I had to drill mine out totally as it was embedded into the housing of the diff. YOu have a make a special tool or buy one from honda to remove the "reverse star" nut around the shaft area. That is where you will find the spindle bearing, at the nose of the shaft.

Here are a few pics of mine and the tool I made.

http://www.fototime.com/{535C700F-44BF-4271-8D92-D3F3D8610798}/picture.JPG

http://www.fototime.com/{D3192E2D-5C18-4348-94BF-0C42D43EEA5D}/picture.JPG

http://www.fototime.com/{E372F76E-EED9-4C0F-B367-31BFDE13057E}/picture.JPG

http://www.fototime.com/{5951EDBC-08ED-49FE-872F-25F778D20877}/picture.JPG

http://www.fototime.com/{18FD2B3B-8129-4606-AA43-4026D8266F85}/picture.JPG

[Dirtcrasher]

Great info guys...thank you very much.
I just managed to get the damn thing off the big red, boy was that fun.
The 2 250sx's were a breeze compared to this old rusted beast. One side of the axle had the nut gauld on it or something (though the threads seemed just fine after removal) so I had to cut it off. Tried to pop the drive shaft back up outta the rear diff and not even close (worth a try) so now its down to the swingarm bolt and the drive housing, couldn't budge either. Frustrated as hell heated swingarm bolt, cleaned it up sprayed with penetrating oil, pounded the heck out of it still won't budge. Heated three bolts on drive housing (allen type) couldn't budge em. Then I turned the beast upside down, pounded each bolt with a hammer three times while chanting "come on ****** ******" and voila they broke loose. I'm guessing I had some better leverage with the trike upside down but I swear the chant helps!

Now for the fun part...the pinion shaft on this diff seems kinda sloppy, not quite as bad but close to the one I'm replacing for what I think is the same reason. UGH.
So far my experience is only these three machines.

1. 250sx #1 Bad one seems like pinion shaft bearing is gone, turns real sloppy to the point that when I tighten up the retaining nut and install it on the bike as soon as it engages in gear it just runs the nut off the pinion shaft and it loses its bite on the pinion gear causing it to spin around the pinion shaft.

2. 250sx #2 Good one on rideable machine now, pinion shaft had very very little slop seemd firm.

3. Big Red Unknown - seemed to work from manually moving axle but not running so I myself have never ridden. Now that its off the bike I see that this pinion shaft seems to turn sloppy too, so I'm inclined to believe it's only a matter of time before this one fails (if it aint already).

Anybody have experience replacing the pinion shaft bearing in these differentials? Seems like it aint too big a deal with the right puller which I of course do not have.

ScottyZJ gave ya some excellent pics and knowledge. If you can weld up a nut/bolt etc etc tool to remove the retaining nut, the rest isn't too bad.

The kits are a good price too, "DADS" on the board has them for a great price and super fast shipping.

These diffs would last FOREVER if guys could just figure out how the water is getting in there. In my case, all the bad diffs I came across were due to a bad swinger pivot rubber boot. But even the rear axle can let water in if those seals go and the ring gear seals go, then the water can get right in. Ya really have to inspect and kee the rear ends tight on the shaft drive machines.

When I put a new boot on, I silicone underneath the boot with the clamps barely tight. Then, the next day I thighten the boot clamps home. I also made a guard to protect my boot because my riding boots are what rips my SX boot along with sticks and branches.

Just make sure to not lose or mix up any and all washers on the ring gear. Thats how Honda shims them to get the right mesh and lots of guys don't know there in there until they clean the parts up and at that point, they mix up the washers.

[Name Brand]

Dirtcrasher - Got any pics of the guard you made for the pivot boot? I'm always interested in making my machine more durable.

Also run the ventline as high up a you can. I put mine into the top of my airbox; no water in the diff since I did so. I also seal up the outside edges of the pivot boot.

My rear diff is from a TRX (along with alot more TRX parts). I forget the ratio but I *think* it's the same as the ES; both machines had twenty five inch tires anyway. For a very short time I ran this diff and a 22 inch tire. 1st and 2nd gear were almost useless and my top speed went way down. I had trouble keeping up with my riding buddies! :crazy: The only thing that worked well with that setup was 3rd gear for climbing dunes (Knik) or climbing hills at the motorcross track. (Kincaid) With 25's and some swinger mods this setup works excellent!

There's info and pics in the link in my signature below.

[cybrman]

Today I took a closer look (or tried to) at the pinion gears on both of the differentials I have removed.

First thing I notice is that the pinion gear seems a bit more worn on the unit that I know to be bad (250sx #1), than the unit I am unsure of from the Big Red.
So now I'm wondering....
Is the play in the pinion shaft normal or should it be very firm and wiggle free? Is my problem the play or the worn pinion gear? or both?

Went out to Harbor Freight and got me a bearing puller and that worked easily enough, top bearing/seal removed. Now I am facing the dreaded keeper nut on the lower pinion shaft bearing. The picture becomes crystal clear now and Scotty's picture make more sense now confirming the martian bolt inserted to prevent lesser mortals from removal.

So I hafta punt this weekend, since I don't have access to a welder here. Gotta go to my brothers house next weekend to build a martian bolt removal tool.
Looks like Scotty's is made from 3/4" pipe and a nut on the end, seems simple enough.
If you happen to read Scotty, let me know the size of the pipe you used for your tool. (Ooh that don't sound good by itself now does it roflmao)

Pictures of pinion gears (http://www.cybrman.com/pictures/06222008differential/default1.htm)
1st is 250sx #1 after removal of pinion gear
2nd is 250sx #1 showing pinion gear on
3rd is Big Red differentials pinion gear
4th is 250sx #1 pinion gear by itself
Some Videos of the pinion shaft movement, they both have about the same amount of slop compared to the one thats on the rider now.
250sx differential pinion shaft movement video (http://www.cybrman.com/pictures/06222008differential/250sx.avi)
Big Red differential pinion shaft movement video (http://www.cybrman.com/pictures/06222008differential/bigred.avi)

[cybrman]

Appreciate any more knowledge i can get.
Thanks.

[ScottZJ]

I was looking around and couldnt find my homemade tool.....:lol: But I will look again today and see if I cant find it. What I did was take the diff with me to the hardware store and found a nut that would work on the star lookin thingy. then I found a pipe that it would fit on and welded it on the end. I also welded another nut on the other side to use to pry it out.

[cybrman]

Now that is a logical approach, taking it to the hardware store (never have to go back to replace wrong size). I can handle that hehe.

Did you happen to take a look at the video and pictures, wondering if my problem is wear on the pinion gear or the play in the shaft or maybe both.
Looking for anyone who's been inside one for their opinion.

Thanks to everyone for all the information.

[ScottZJ]

That is really hard to tell but looks to me like the bearings. Remeber the stub of that goes into a hole with needle bearings in it. So is they are smoke, (which most are), then you will have tons of play. You should be able to remove the side bolts and view the inside. You can tell if the gears are toast.