Toasty Final Drive

[conquest87tsi]

I just got home from a 160 miles ride and noticed that my final drive is very warm. Like can only hold my hand on it for 3 seconds kind of warm.

Last saturday I removed the wheel to replace the tire, and while I had it apart I removed the final drive, cleaned it and the wheel splines and relubed with grease. The heat is localized at the differential(Final Drive). The heat is not from the brakes as they are touchable.

I haver not checked the fluid as I can't get the cap removed with an allen wrench. Even when I heasted with a torch. I'm going to go pick up a 3/8 socket hex set as soon as I'm done typing here to try that. My father did say he checked it a month ago, but I don't believe that as he is almost half my size and I don't see how he could tighten it so tight. That is unless he used a 3/8 drive.

ANyway, I am wondering how hot the final drive normally gets. I have never knowingly felt it before. There is no play in the wheel and I don't think this is due to a wheel bearing. I did squirt some grease into each bearing. The left side bearing I used a needle greaser since I couldn't get the seal off. Is this abnormal to get that hot? I don't remember a car's rear diff ever getting that hot.

[conquest87tsi]

Grease

Oh, and I did use the red wheel bearing grease. Since that is whaI had around.

[TopCatGr58]

Hey there,

The FD's can get a bit warm, but I don't know exactly how warm/hot, as I also have not checked or tried to touch it after a ride.

As to the filler plug, many techniques have been suggested in other threads, PB Blaster, then heat gun, then cold chisel to get a bite into the top/edge and a few hits will usually loosen it enough to allow you to then use the wrench. THEN after you get it out, replace it with a hex head type bolt, not a hex socket head, and use a nylon washer.

T.C.

[DGXSER]

While the final drive will get warm, it typically would not be so hot you can barely hold your hand to it (unless of course your a total complete whimp when it comes to heat ).

As to the grease to use, I use a moly paste type grease on both input and output splines of the FD.

You definitely want to check the fluid level in there. I do not care who tells you they checked what, only believe what your own eyes have seen.

[CaptonZap]

At the Durango rally last summer, I took some temperature readings on the final drives of a number of bikes after a 20 mile 50-60 mph ride, and the average for six or seven bikes was around 130 deg, with 80 deg ambient air temps.
That said, PLEASE, get the plug out and change the oil. Real soon. The final drives are a marvel of engineering and manufacturing, and deserve the best care that we can give them. Kept full of clean lubricant, they will last forever, or at least till the cows come home. CZ

[motoman]

The allen hole isn't gonna work for U. Your gonna half to take a sharp chisel and go straight in and make good deep divet in the top edge of that plug, then hold at an angle and one sharp blow will pop it loose. Go to your local Ace or Tru-Valu and get a nice polished shoulderd hexed plug along with two of the hard fiber gaskets next to the plugs. I use two of the thick fiber fitting gaskets in the final as it is a recessed seat. One gasket for the middle drive. They both are the same size and you should at least check it to, or better yet change out the fluid in both drives going back with 75-140w Royal Purple syn. Do NOT use the 80-90w if going with a synthetic. With these lubes the drive temps will be greatly reduced. Heat=friction, plus the gear whine will all but dissapear.

[conquest87tsi]

Final Drive

I got a 3/8 drive hex socket and the plug came loose at around 50ft-lbs(using calibrated elbow) with a nice snap. No problems there. The level was fine, but very dark colored. When draining I noticed the plug was very fluffy. A lot of black material on the magnet. About 1/8" think all the way around. I decided to remove the final drive again to check splines and then decided to inspect the gears against the Clymer's instructions. There was a bit of black material in the housing. The only other strange thing I noticed is that it appears that the bearings outer race is seperated from the bearing. The outer race is stuck on the shaft and I could see the rollers inside the bearing.
Is this how it is supposed to be?

Has anyone taken a final drive apart?

I put everything back together. Filled the final drive and at 10:30 was putting away tools and noticed that damn shaft to final drive spring on the bench. Did the same thing when I changed the tire. Stupid spring.

Anyone have any advise?

Like you say, friction=heat, and I don't want to risk the rear end locking up.
I do have a spare final drive from my parts bike, but it has 26K on it and mine turned 16K today. Kinda counter intuitive to make that swap.

[conquest87tsi]

Oil & Grease

So I stuck with the grease I had. It is as good or better than moly grease, plus has a higher temp rating. Also I went with conventional 80-90.

[trbig]

So I stuck with the grease I had. It is as good or better than moly grease, plus has a higher temp rating. Also I went with conventional 80-90.

So why do you ask for opinions if you are going to just do whatever you were going to do anyway? Regular red grease is nowhere near as good as molly grease, and regular dyno rear end oil is LIGHT YEARS inferior to new synthetic lubes, which will help the final drive (And middle drive) run much cooler/quiter.

It's your bike, but there's knowledge on here learned through many many years of trial and error that you've just pissed away. As stated.. Heat= friction= wear. That metal shavings material stuck to the plug you took out should tell you how well your train of thought works. Or.. are you the type that likes to do the same thing over and over and expect different results?

[CaptonZap]

I got a 3/8 drive hex socket and the plug came loose at around 50ft-lbs(using calibrated elbow) with a nice snap. No problems there. The level was fine, but very dark colored. When draining I noticed the plug was very fluffy. A lot of black material on the magnet. About 1/8" think all the way around. I decided to remove the final drive again to check splines and then decided to inspect the gears against the Clymer's instructions. There was a bit of black material in the housing. The only other strange thing I noticed is that it appears that the bearings outer race is seperated from the bearing. The outer race is stuck on the shaft and I could see the rollers inside the bearing.
Is this how it is supposed to be?

Has anyone taken a final drive apart?

.

I'm sure that you know which bearings you are talking about, but what you describe doesn't make a lot of sense.
There are 5 bearings in the final drive. (FD). Which one are you talking about?
There can be an outer race stuck in a housing, there can be an inner race stuck on a shaft, but there is no way for an outer race to be stuck on a shaft.
Go to Catatonic bug's site, and download the manual for the final drive, and it has the parts labeled, which you can then describe, and we can figure out what you are talking about.
Yep, the black fuzz on the magnet was all the chips and wear particles that, if they weren't on the magnet, would be floating around in the oil, acting like an abrasive fluid inside your FD, something that you would like to avoid.
If you are the first person to take the drain plug out since the bike was new, that amount of fuzz is not out of limits. The machining tolerances were not that good back in the day, which was why a break in period was prescribed. It allowed the roughly machined surfaces to grind each other smooth, and the wear particles were drained out with the break in oil. Now days, the machining processes give a much smoother finished surface, and do not require as much break in to attain the running surface finish needed for longevity.
If, after you put fresh oil in there and put 10 or 15 thousand miles on it, it shows that much fuzz again, then you should do some serious looking inside, and figure out what part is coming apart. CZ

[skids]

I believe that I read a post that said when then rear-left bearing is too worn, it causes the rear differential to rapidly wear. It might be worth searching through the threads, but I think that it will be in the threads about the converted final drive.

[skids]

P.S. the final drives do get quite warm normally. Metal wear in the oil is not good however.

[conquest87tsi]

CaptionZap,
Your right, it was the inner race, my bad.

Trbig,
I may very well use synthetic oil in the future but am sure as hell not going to waste any $10+ a bottle oil while I'm trying to figure out if my final drive is bad. I have a pretty good idea that I am the first owner to replace the final drive oil. The bike had 14k on it when i bought it.

I have decided to do the XS750-850 final drive swap anyways so I'm glad I didn't waste some synthetic oil.

Thank you so much for your wisdom Trbig, you are so wise. I used the grease I had since the temp rating was almost twice that of the moly grease I saw at the store and since my final drive was extremely warm I didn't want to boil the grease.

[trbig]

Thank you so much for your wisdom Trbig, you are so wise. I used the grease I had since the temp rating was almost twice that of the moly grease I saw at the store and since my final drive was extremely warm I didn't want to boil the grease.

My apologies. It's obviously YOU that's so wise and heat rating of grease is absolutely the only thing to consider...




http://www.bobistheoilguy.com/moly1.html



If your bearings get anywhere near the lowering temp of the molly grease, you've got a serious problem that even high heat grease isn't going to help you with, oh Wise One. I stand by my original statement. Moly grease is better, as well as full synthetic. Dyno oil is @ $9 here and full synthetic is @ $17, so again my apologies for assuming less than $10 was not going to break someone by adding the best stuff for the bike. But again... why ask for opinions if you're just going to do whatever you want anyway?

[BA80]

Oh geeze, now a grease thread......