MR2 Owners Club Forum banner

1 - 20 of 43 Posts

·
Registered
Joined
·
2,513 Posts
Discussion Starter #1 (Edited)
I pulled my trans (1993 MR2 Turbo) yesterday as I am swapping trans again (that's a long story, more on that below). I decided to inspect my clutch and flywheel at the same time. They have less than 4000 miles on them, and I replaced the clutch in May of 2011 (it is Oct of 2012 as of this post).
Flywheel surface, disk pucks, and pressure plate friction surfaces all look good. However, I discovered massive fretting of the clutch hub splines.





The input shaft shows indications of fretting in that the surface is coated in the oxidized powder. However, the splines appear to be fine, and I felt them as well. Feeling them reveals no abnormal wear on the splines, i.e.: I drug my fingernails from the part of the spline not engaged to the clutch disk hub to the part engaged, and there were no steps from wear. This is not obvious from observation, or from the photos, which is why I felt them. The photo below makes it appear as if there may be a step due to fretting wear, but there is none.






From my Machinery's Handbook, 24th edition, page 2053:



My summary: low amplitude oscillation movement between the male and female splines, results in fretting
Once you get a little bit of oxidized steel (rust, but not caused by corrosion), the powder increases wear of the splines dramatically, as it acts like sand in the works.



I also found this paper online:
"Surface Durability of Coaxial Splines" Nembered page 18 (pdf page 26) starts the discussion on fretting:

http://fcp.mechse.illinois.edu/reports/FCP_Report177.pdf


Background: My 1993 E153 w/LSD (original trans, which I will call Trans #1) had about 100 to 110K miles on it and has not shifted very well since I bought the car in 2005 with 85k miles on it. I have long thought that the synchros were worn. At 93K miles, I replaced the OEM clutch with a Spec Stage 2+ clutch kit. This is a kevlar faced disk, with a sprung hub.

In 2011, during some "too" enthusiastic shifting, I jammed up 5th gear. I started looking into rebuilding my trans, but discovered it was a more complex of a task than I wanted to tackle at the time. Its also exceptionally difficult to find all the part numbers for all the little parts needed.

Instead, I bought another 93 LSD E153 (trans #2) from a board member that claimed it was rebuilt. That was april/may of 2011.

I replaced the Spec clutch with the clutch masters, after the spec clutch had about 20k miles on it. I burned up the spec getting the car home when I destroyed 5th gear on trans #1. I still have the disk and PP from this kit. Inspection of this disk a few minutes ago reveals no fretting of the female splines. However, the hub springs have partially worn through, and any more wear by the springs would result in this disk throwing its springs (from what I gather, a common problem with specs). This is why I went for an unsprung hub when I swapped trans.

I installed a Clutch Masters Stage 4 (power plus 1 Pressure plate) with 6 puck unsprung hub disk at the time, and new throwout bearing. I also replaced the rear main seal on the 3s, but this is just for info, and is not the cause of any issues.

I pulled trans #1, and I put the trans #2 in, and drove the car up until a couple of months ago, when I discovered the input shaft seal seemed to be leaking oil badly. Before the leak started, the trans shifted great. After I had the trans in for 2-3k miles, I found that just after shutting off the car when parking (engine/trans are warm), it would dump oil out of the bell housing area--out the drain hole at the bottom of the bell. I stuck my finger in the oil and verified it was purple in color (Royal Purple) gear oil, and smelled like gear oil. Definitely not engine oil (recall I replaced the rear main seal as well).

I decided to roll the proverbial sleeves up and dig into rebuilding my original trans (trans #1) That was a huge project but I am almost done with it. I had to create my own guide with drawings and part numbers just to figure out which parts I needed and did not need. I did pretty good, and only ordered one extra part I did not need, but was able to return (extra inner synchronizer ring). It turns out that the No 2 clutch (synchro) hub had "sprung" 2 of its 3 springs that provide pressure to the 3 shifting keys. No 2 hub is for shifting 3rd and 4th gear. This explains why my trans never shifted into 3rd or 4th very well as long as I have owned the car. The springs were laying in the bottom of the case. These springs are very small, and look like pen springs, but are much stiffer. During my rebuild, I corrected this design defect, and the new springs are very unlikely to pop out of place.


At any rate, I pulled trans #2 trans yesterday in preparation for swapping trans, and discovered the fretting of the clutch disk.


Possible causes:

Input shaft "walking around":
Input shaft bearing is damaged or worn out. They obviously did not replace the input shaft seal of trans #2 (because it was leaking). It is possible that the input shaft was damaged or just plain worn out and they did not replace it either.

Input shaft bent
If the input shaft were bent, it would cause low amplitude oscillation movement between the male and female splines, resulting in fretting.


Damaged disk:
I could have bent the clutch disk during installation of the trans. This is super easy to do, as putting the trans onto the engine, while the engine is in the car is super difficult. If I bent the disk (remember its solid hub), then the female hub splines will "wobble" relative to the input shaft.


Insufficient lubrication of the input shaft splines, and the female splines of the disk hub: According to Sachs, its really important to lube this area at assembly time, to prevent fretting. I found this in their literature and tech bulletins by googling around. I am pretty sure I used a light coating of never seize compound when I put the clutch on.

Misalignment of the trans:
All transmissions have a slight amount of misalignment with the engine in any car. The dowel pins align the trans to the engine, but the dowels can be placed slightly off (but usually within manufacturing tolerances). If they are outside of tolerance, the axis of the trans input shaft and the axis of the crankshaft could be off by enough to cause fretting of the clutch disk splines.
Trans #2 was one I bought off the board, with unknown history. Seller claims it was rebuilt less than 6k miles before I bought it. I will be able to verify that when I disassemble to replace input shaft seal and bearing. Possibly the dowel pins are slightly off for this trans, possibly at the extreme end of the manufacturing tolerance range, or just plain outside of tolerance?

Trans #1 obviously had no misalignment issues, as the OEM clutch (0 to 93k miles) and the spec clutch (93k to 110k miles) had no fretting issues.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #2 (Edited)
So a couple of questions:


Would a sprung hub type of disk help prevent this failure mode? Recall the spec clutch did not have any fretting. Unknown if this is because Trans #1 had no alignment issues.


Is there some kind of "super grease" available, that is made for clutch/input shaft splines? It would have to be super sticky to keep it from getting slung out into the clutch friction surfaces, contaminating them, and it would have to be able to withstand very high temperatures, and it would have to withstand very high shock loading.

Any other fixes for fretting of splines that I should consider?
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #3 (Edited)
Link to Sachs tech bulletin that contains discussion about lubing clutch splines
Also talks about bent disks causing fretting
(page 29)


http://www.zf.com/media/media/en/im...Fahrzeugteile_im_Pkw_Antriebsstrang_DE_EN.pdf



Apparently, BMW motorcycle guys have issues with spline fretting. As far as I can tell, more moly = higher temperature range


Moly is a solid lubricant which can withstand extreme pressures, and temperatures up to 1500 F



found this (look under Spline Lubricants)

http://motorcycleinfo.calsci.com/Shaft.html
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #4 (Edited)
Honda Moly 60 20% Molybdenum Disulfide Part number 08734-0001 eBay, Amazon
Moly is a solid lubricant which can withstand extreme pressures, and temperatures up to 1500 F
http://www.ratherbe.us/Moly60_MSDS.pdf



LocTite Moly Paste, 65% molybdenum disulfide to 750 degrees F
fairly cheap compared to alternatives. Available all over the place (Amazon, etc.)





Yamalube unknown moly content
ACC-MOLDM-GS-10
Extreme-pressure grease lubricates high loads, Non-corrosive, water-resistant, exhibiting low-friction properties that protect against wear and galling in difficult operating conditions. Use this grease where specified in the Service manual to use grease "M".

This extreme-pressure grease lubricates high loads at various speeds. Non-corrosive, it??TMs water-resistant, exhibiting low-friction properties that protect against wear and galling in difficult operating conditions.




Dow Molykote

Dow Corning Molykote 321 dry film lubricant (spray)15-35% Moly, made for splines, gears, threads, press-fitting, 840 degrees F

Molykote M-77 Part Assembly Paste, >60% Moly, made for splines, gears, threads, press-fitting, 750 degrees F


Molykote G-n Metal Assembly Paste/Spray 15-35% Moly, made for splines, gears, threads, press-fitting, 750 degrees F

Molykote 3400A Corrosion Protective Coating, 10-30% Moly, made for splines, gears, threads, press-fitting, 900 degrees F



Not for splines

Molykote P-37 Ultrapure High Temperature Paste for threads 2550 degrees F
Molykote 1000 High Temperature Anti-Seize Paste for threads 1202 degrees F
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #5
I sent the photos to Clutch Masters and a description of the problem.

Here is what they said:

If the vehicle is making slightly more power above than stock and driven on the street then you should NOT be using this clutch kit on the street. The FX500 is intended for high horse powered vehicles that will be used on the track.

the reason the spline on the disc is wearing out like that is due to the missing springs on the disc. If you would have springs on the disc the springs would absorb the shock on engagement and will reduce the stress on the splines.

you can always send the clutch kit back to have it changed to a FX400 and you will just have to pay for the new disc and shipping.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #6 (Edited)
I took another look at the input shaft. Grabbed it and jiggled it to see if the input shaft support bearing was loose. Did not seem to be.

I think the permatex anti-sieze was a poor choice for lubing the splines. I am going to a high moly content (60% or greater) paste this time.

I am going to make absolutely sure I don't bend the new clutch disk I just ordered.

I am going to use an sprung hub this time (though I don't think this was the issue, at least by itself).

I will check runout of the new disk, and straighten the new disk if it arrives bent (could happen in shipping).

I am going to scrub the input shaft splines really good with steel wool, wire brush, scotch brite and use brake cleaner to get rid of grit (making sure none goes down the shaft to the seal, which could ruin it---come to think of it, I could clean the splines and lube them before installing the shaft into the trans).

and I am going back to my original trans, which I know does not have dowel alignment issues, as both the OEM and Spec clutch hub splines were fine.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #7
Another part of the MR2 Turbo that I have seen some fretting is at the axle splines that slip into the rear hubs.

After I thoroughly clean the male and female splines, I am going to use the moly lube solution for them, along with lubing the large axle retaining nut that gets tightened to 217 ft-lbs.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #9 (Edited)
So here are my planned fixes:

Rebuilding trans #1 (doing that now).

Replace input shaft bearing--to replace the seal, you have to pull the bearing. The bearing puller I currently have destroys the input shaft bearing (because it hooks on the rolling elements), so I will replace it with a new one.

Check input shaft to see if bent. This is easy with my dial indicator.

I will attempt to check dowel pin alignment. This may be pretty difficult as I do not have access to a 3 axis coordinate measuring machine (though I only need 2 axis). The engine (3s) is still in the car as well, and needs to be checked against the transmission bell pattern. This is made more difficult by my intended method of measuring due to the flywheel being in the way.

I will make sure I do not bend the new clutch disk

Clean all oxidation from input shaft. This stuff acts like sand in the works. All MUST be removed.

I will use super lubricant on the new disk hub splines and the trans input shaft. I bought some Krytox. Its good up to 500 degrees. Those tests on http://www.sandsmachine.com/grease_t.htm really convinced me.

The new disk has a sprung hub. From my research, sprung vs unsprung should not make any difference with respect to fretting. So I decided to go this route to make life easier for my trans and CV joints

I am also using 65% moly super lube (loctite moly paste) on the axle splines at the hub, and a little krytox on the nut for the axle, so I can get this splined connection as tight as possible within the specified torque (217 ft-lbs). I am using the loctite moly paste on the axle splines because there is a lot more surface area (especially with 2 of them) than the clutch splines, and the moly paste is a lot cheaper than krytox.

Loctite Moly paste is good to 750 F (not that the axles get that hot), but is not as slippery as krytox.

Molybdenum disulphide

http://en.wikipedia.org/wiki/Molybdenum_disulphide
 

·
Registered
Joined
·
2,138 Posts
The anti-seize stuff you used is essentially a lapping paste. There are small metallic particles suspended in a lube. This may have been the cause of your fretting. As you pointed out, it would be advisable to use some kind of thick viscuos lube instead.

Another cause might be that the splines were improperly heat treated. We know that quality issues on automotive parts do crop up from time to time. Heck we see quality escapements on airplane parts every day here where I work.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #11 (Edited)
Yes, I learned that normal anti-seize has micro metallic particles (like copper and aluminum) in it. I think it did not work as a spline lube simply because its just not that good of a lube. If you go to the screw test link I cited above ( http://www.sandsmachine.com/grease_t.htm ) you will see that anti-seize did not do that great. I don't think its nearly as good at 65% moly paste. It obviously was not good enough for clutch splines, and it was definetly a mistake to use it.


I just finished rebuilding trans #1 about 30 min ago. At the final steps, the BGB actually states that we should put Molybdenum Disulphide grease on the input shaft splines, and clutch hub.

The Loctite Moly Paste I have is 65% MoS2 that would work great. Its also good for 750 F.

I decided to use the Krytox on the clutch disk splines and input shaft splines. Its more slippery than 65% moly paste. In the link above, he states that Nascar mechanics found krytox on splines reduced the temperature of the splines by 150 F. So, it must reduce/eliminate a lot of heat generated by friction of the splines rubbing on each other.

This along with the "binding thread screw test" in the other link cited convinced me that Krytox is super grease. I wish the would have tested the Loctite 65% moly paste as well. I would duplicate the test myself, except that I don't have a gauge to measure 4000 lbs of force to squish the nut.


Krytox is good up to 500 F, and I bought a tube of the stuff.

Its super expensive. I got 2 oz for $25 shipped, but most places I saw sold it for $40 for 2 oz. This is why I will switch to moly paste for axle splines.

Inside the trans, I also used moly paste for the large nut on the end of the output (?) shaft and on the screws that hold the bearing retainer plate. I was going to reuse some of the old screws that hold the retaining plate, but during torquing with a torque wrench, I could feel one of them starting to break the head off. I quickly backed it out, and found that I was correct. After that I switched to all new screws and lubed the underside of the heads with moly.

I used a little moly for 5th driven gear (its pressed on), and synchro hub #3 (pressed on as well) to make them slip on easier.

I used regular (cheapo) anti-seize for the bolts that hold the case together. In all cases where I lubed bolts, I also used loctite, so I had to be careful to keep the 2 separated (loctite on threads, but anti-seize under head of bolts).
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #12
I'm not sure they even heat treat clutch hubs after they broach the splines. They may leave them soft on purpose as clutch disks or hubs are relative cheap compared to input shafts (not to mention the labor required to replace the input shaft).

I mean they might, but they did not appear to be. I could try a center punch into the steel of the hubs of both disks I have and see how hard they are.

The paper I cited above talks about making the female splines of a softer material than the shaft with male splines.
 

·
Registered
Joined
·
575 Posts
Holy crap i though that i was the only one with this problem and act told me the same thing that cm told you. I replaced my disc with a sprung one and it took more time but its doing it again.

After reading this i think my tranny is the problem. I replaced the shafts iwith st205 ones in it just before this problem started ! Something is probably wrong.
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #14
I think its safe to say that sprung vs unsprung won't make a huge different in terms of fretting. The sprung might last a little longer, as the pressure on the spline teeth is reduced.

But if the splines are RUBBING on each other (bent shaft, bad bearing, bent disk, misalignment of trans to engine), then all the springyness in the world won't help. Read the ME paper I cited above, starting on the page I cited.

Check your input shaft for straightness. You need a dial indicator for that.

IMHO, the most likely culprit is bent clutch disk. This is easy to do when putting the trans into the car, especially if the engine is still in the car (as opposed to joining the trans to the engine when they are both out of the car).

Do you remember what kind of lube you used on the splines and the clutch hub when you put your clutch in? How much you used?
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #15
As an aside note, I am disappointing that the clutch companies don't know what they are talking about when it comes to fretting. I even asked to speak with an engineer at clutch masters, but they wouldn't put me in touch with one.
 

·
Registered
Joined
·
575 Posts
cbulen said:
As an aside note, I am disappointing that the clutch companies don't know what they are talking about when it comes to fretting. I even asked to speak with an engineer at clutch masters, but they wouldn't put me in touch with one.
Same here !! Very disapointing
 

·
Registered
Joined
·
2,513 Posts
Discussion Starter #18
cbulen said:
The paper I cited above talks about making the female splines of a softer material than the shaft with male splines.
I need to correct myself. THe paper says both surfaces where the fretting occurs should be hardened.

However, the other statement I made still applies, as replacing a disk with fretting failure is easier than replacing the input shaft.
 

·
Registered
Joined
·
575 Posts
I have an other tranny laying here but the reverse dont work, im gonna repair it and install, my engine is out anyways.

On another note, what type of puller do you use to remove the fifth gear?
 
1 - 20 of 43 Posts
Top