Need a few tips about troubleshooting 250sx rear end noise and rebuild

[v30Magna]

I picked up a 250sx about a month ago, and I've been putting it back to riding shape. It has been running and driving just fine (I towed my brothers' trx250 1/2 a mile Thursday), but the drive shaft boot has a tear, so I've gotta replace it. The rear end or drive shaft (I can't tell which) seems to be making a clunk, almost a ping, which gets louder the faster you go. It actually isn't even audible when your putting around in 1st gear. I think it's the drive shaft, but I don't know for sure. How can I test it to figure out if it is the issue?

When I do the boot (which will be soon), I want to repair any damage caused by the torn boot, and I want to fix the ping/clunk. Can anyone give tips and/or procedures for checking the drive line stuff, as well as what stuff to check?

Oh yeah, the rear seems to "whine" about twice as loud as my brother's '85 trx. What would be the checklist/ fix it for that?

[jeswinehart]

Hi James.
First order of business, if you have not already done so,,, is to change the differential oil
with fresh 80/90 weight. If not much in there or really nasty looking change it again in the very near future after getting a few hours on first oil change.
Easiest to drop the rear differential skid plate (2 bolts) to access differential drain.
If you are definitely going to replace the drive shaft cover, cut the old one off with razor knife and you will be able to see how much, if any slop/play it might have (should not have very much if any) ~ you can make the call on whether it is worn out or not.
To install new cover, slide the U joint back just enough to be able to wiggle new boot/cover on.
Hopefully this will all that is needed, but maybe not if way to neglected.

john

[tri again]

x2 with Jesw.
Those drivelines/shafts were touted as maintain free
(as opposed to chain drive) so most have been ignored.

If it's an 85 sx there's only about 3 Point 3 ounces of (hypoid) gear oil
so there isn't much to start with.

You may be able to get to the 10mm head drain bolt from the side
and there's a fat copper washer that usually falls off.

I put neodymium magnets on all my drain plugs to catch
metal. They are so strong they simply grab onto the bolt heads.

Whatever you do
DO NOT loosen the allen heads that hold the right angle final drive
from the side of the engine to get the driveshaft loose.
DC will tell you that there's a thrust washer deep inside the cases
that has a very specific orientation for an oil passage and NOthing to fool with.


Driveshaft has enough room to get out of the way altho
I had my swing arm bearings apart so that may have helped.

I've heard those boots are still avail but may have 2 different part numbers.

Perhaps the search key will work for you?
service manual
may pop up as a clickable link for you too.

Driveshafts with u joints seem pretty common
and bearing replacement in the rear axle, altho not
real fun, is do-able and has definite bragging rights.

I just got a whole sx parts trike for 90 bucks delivered
so don't worry too much.

[Flyingw]

Based on what you describe I ponder a couple of things. The easiest solution is bearings but you have to have special tools to disassemble the diff. I got my hands on 2 of the 3 tools needed to disassemble the diif and this weekend I was able to completely disassemble 3 diffs as test candidates. The tool I dont have is the tool for pulling the pinion shaft and bearing out of the case but I was able to get the shaft out anyway. I also needed a blind hole bearing tool for removing the roller bearing and a split bearing tool to get the bearing off the pinion shaft. My point to this is dont tear in to the diff unless you know what your getting in to.

Now, for the boots. Honda does still have boots in stock for the SX only. When they sell out of them, there will be no more from Honda. My advice to you SX guys, order a spare or two (18.00 from Service Honda) and put them away. The ES boots are discontinued and yes they are different from the SX boots. From what I can see, the molded angle of the boot is different (slightly) so in the absense of ES replacement boots, install an SX boot. It better than a damaged boot.

The correct way of handling the boot in your case is to unbolt the entire rear end at the swingarm pivot and rear shock. Take the two rear brake cables loose and fold out of the way. Support the trike under the motor and remove the bottom shock bolt. Then remove the swingarm pivot and roll the whole rear end away from the frame. This will let you pull the propeller shaft out and clean it up. Get yourself a can of PTFE dry film lube. You can get it at any Fastenal and some auto stores. Clean the propeller shaft as clean as you can get it. Once clean, spray the propeller shaft down with the dry film lube, soak it and let it dry. Clean out the tube in the swingarm where the propeller shaft goes through. Clean it out and spray the inside of the tube with PTFE as well.

Now would be the time to decide if you want to refresh the rear end and diff. If you neglect the diff and it blows itsself apart, you got a 360lb paper weight so take care of your differentials. I can do the rebuild on the diff if you want. I'm sure we can work out something inexpensive as compared to buying a used diff with perhaps the same problems. It should be noted that the SX/ES diffs are simple in design, they will fail when neglected. They are fairly robust but they need serviceable bearings and seals. As I mentioned earlier, the diffs require special tools so average Joe trike mechanic cant get them apart to change the pinion bearing so if you have a diff with bad pinion bearings, you're shopping for another diff.

IF your pinion bearings are good, then you can replace the ring gear bearings and seals. The kits come with the seal for the propeller shaft end of the diff and that should be changed too but its not easy to get out without damaging the case. I cut them with a cold chisel then pry them out. Water in the diff comes from this area if the seal is bad.

As I said, if you're going to pull the diff off, you might as well do the axle tube bearings and seals at the same time. If you decide to, we'll continue this conversation. There are some other parts that will need your attention before reassembly.

[v30Magna]

Geez, sounds like rocket science...

I guess I thought it would be a little easier, but I'm very grateful for all this information.

I can get around the blind hole puller, a slide hammer with the little hook tip (not exactly sure of it's proper name) will do that. I looked up the split bearing tool ($38), but since I have no experience with split bearings, I can't get mental picture of the work.

How about trx250 boots as replacement? Just asking to know about interchange.

I guess I need to take a look at the drive shaft and seal 1st, and then get back to you guys. I'll have to wait till next week to order the dust boot, so it'll probably be 2-3 weeks before it's here and I begin this job. I'll keep you posted though.