What is normal rear drive line lash in a 1Ga?

[TrevorS]

I've been listening to a clunk from my rear drive train for years (even when the car was very young -- now aprox 130 Kmi) and I've been told several times by Mitsubishi dealership people it's normal. This occurs without any acceleration to speak of and is clearly drive line lash.

I have the left side raised and inspected the drive shaft joints. The Lobro looks perfect and exhibits no lash whatsoever when hand torquing the two sides against each other. The two forward U-joints have the barest amount of flex in them when hand torqued, the rear seems to have slightly more, but still slight. I tried measuring how far the tallest part of the front-most U-joint moves when the shaft is rotated through the lash, and came up with about 3/32" to maybe a smidgen more. When I rotate the shaft through the lash, there is a distinct clunk at the transfer case end, but the differential isn't delivering that rotation to the rear wheels either (right wheel down and my free hand on the left lug bolts), so the lash is present at both ends.

Anybody know anything about this? How much drive line lash really is normal on these cars (1990 GSX)?

FWIW -- The front half axles are brand new, the rear differential has an LSD, there's pretty fresh Pennzoil Syncromesh in the manual transaxle and transfer case, plus similarly fresh Royal Purple in the differential. Shifter was in first gear and the car has never been driven hard -- no racing of any sort.

 

[TrevorS]

To perhaps further clarify -- the issue has nothing to do with anything even approaching "heavy acceleration". Gently moving out from a stop can cause it if at the stop, rearward car roll (doesn't take much) restored the dead zone. I describe it in detail above. There is lash (or play if you prefer) in both transfer case and differential, and the resulting clunk has always been there (though I may hear it more often now and perhaps it's a little louder). I understand the '90 AWD transfer case has a 22 spline input shaft. I don't know if that was also true for the '91, but I'm guessing there were reasons for the redesign that went beyond bumping the spline count to 23. Perhaps eliminating the clunk being one of them?

These two links provide examples of what I'm talking about (the proviso in the first is associated with an auto transmission, mine's manual)
http://www.signonsandiego.com/uniontrib/20...d17clkclak.html
http://blogs.insideline.com/roadtests/2010...eline-lash.html]Straightline

It appears to me driveline lash is an "idiosyncracy" of the '90 and perhaps '91 Eclipse AWD, though I'm not sure how it's apportioned between the transfer case and differential. I'd like to get some feedback on this -- I realize 3/32" or so doesn't seem like a lot, but please believe me, it's very audible when the engine takes up the slack.

 

[GSLENK]

thats like what? 80 thousand miles? I know you may not want to do it, but it might be U-joint time. I would try that first. its the cheapest part that could be affected here...

Are you m/t or a/t? remember m/t has a sprung disc clutch... that spring takes up some slack sometimes(to me its unnoticeable...)

 

[TrevorS]

thats like what? 80 thousand miles? I know you may not want to do it, but it might be U-joint time. I would try that first. its the cheapest part that could be affected here...

Are you m/t or a/t? remember m/t has a sprung disc clutch... that spring takes up some slack sometimes(to me its unnoticeable...)

Thanks, but please re-read my first post. This is not just a think piece, I lay under there on my back and checked the joints and rotated the drive shaft. Also, 130 Kmi translates into 130 thousand miles ! And yes, it's a manual transmission, as per my PS, it was in first gear when I climbed under there.

 

[TrevorS]

Finally, found someone else's post about the same problem!

My 90 TSI clunks pretty bad when I start from a stop. There is A LOT of play in the rear diff. It is a metal to metal noise, it does not sound like it is hitting the body. SO I don't know if yours sounds similar, but I can get down there and manually make the noise happen as well by twisting it....

drive train clunk - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com

BTW -- I'm aware of the "thump" VFAQ. Climbed under again to specifically study the carriers. They both show a little crazing in the rubber, but not deep, and the rear looks the better of the two. I tried pushing/pulling the shaft as far as I could to the sides and up and about 1/8" is all I could manage (both carriers). I'm pretty sure I've never hear the vfaq "thump" problem -- mine is a "clunk" (metal-to-metal), no real acceleration needed. (I've a long history of being very easy on the accelerator !)

 

[TrevorS]

Well, very disappointed with the total lack of genuine assistance, information, and even discussion from DSMtuners members ! You'd think that 1G rear drive shaft lash and differential/transfer case limitations were a closely held secret, and it would be self condemning to divulge anything. Thanks for naught gang. Obviously, despite it not being an unknown issue, it's off topic in this environ !

 

[vinnio]

Hey man. Some people just don't like answering these questions here. If you asked about recirculating a blow off valve on the other hand, watch out!! w/e Sometimes you just have to wait a while for the right people to log in!

I have a 2g awd auto and every so often while shifting from reverse to drive or vice versa I get a nice clunk. My best explanation for this is purely how the car is designed.

Think in you're head about how many splined connections there are from the transmission back. All those little gaps in those splines added together equal one sizable amount of play. Personally I'm not concerned with it on my car because there isn't any one noticeable weak point (i.e. a lot of play in the rear end, u-joint's, etc)

This might help explain it for you a little. If you're still concerned I can look up some actual specs on All Data this week. But like you're dealer said, it sounds normal.

Best of luck chief.

 

[viperlp01]

All the things you are looking for is available through a google search. The term I think you are looking for is differential back lash. The proper way to check back lash is with a dial indicator and the diff cover off. I want to say normal back lash is between .008 and .015 but no less than .005. For some reason that number stuck in my head.

Also grab the driveshaft and move it around. Have someone look under the car while you move from N to D and see if there is any weird engine movement of driveshaft movement.

 

[ed1380]

It's because problems like these are pretty rare. The thump could be from the rear diff bushing wearing out, but that should only be during heavy acceleration. It could be from the driveshaft carrier bushings or improper lash in the transfer case.

 

[TrevorS]

Just want to say thanks for same actual engagement with my thread, kind of a relief if you will ! Relative to the second response, I've searched plenty and it's apparent you didn't read my posts, since if you had, you would know I've very definitely placed my hands on the shaft. Response without taking the time to understand the concern is far from helpful.

I'm not trying to take anyone on here, I'm trying to find out what causes the problem I'm experiencing. My thread title is an entirely valid question. If you have a 1G GSX, how much drive shaft rotation can you achieve by hand before causing the rear wheels to start to turn?

PS. It's looking like I probably have a lash issue in both my transfer case and differential, however I've never been abusive in any way to my drive train, and so naturally questions arise. What is the experience of other 1G owners, especially 1Ga?

 

[TrevorS]

Drove the car for the first time since installing the new front half axles and completing the brake upgrades. Car felt great, but there was exactly one clunk I heard during the run while I had both windows partially open. It occurred after I slowed at the base of a hill where there were cars on each side and some people and I needed to be especially cautious. After getting past the hazard I started to accelerate a little and immediately heard that distinct clunk from underneath -- it sounded just like it was coming from the transfer case, not the differential. Not sure what the deal is with the differential lash, but seems to me the transfer case is the prime offender.

 

[TrevorS]

Well, 1G population continues to be mum -- not at all encouraging for this forum! You guys got something to hide? Or you just don't give a damn? Sorry if I seem a tad aggressive, but this is my car and yes, I'm increasingly disappointed in y'all -- not a mensch among you?

In any case, put the left side up on stands with the LF wheel and down pipe removed. While under, I listened to the transfer case with my head directly under it. Sounds horrible in there at the end of the lash travel -- a combination of steel-to-steel clunk and something that sounds like a piece of tin being tweaked. Wouldn't have thought it could make a sound like that (and yes, it's lubricated). Some kind of bushing issues? Anyway, I expect to take it off the car tomorrow -- first time I've ever fooled with a transfer case, so should be interesting.

 

[DSMnoobsause]

Well, 1G population continues to be mum -- not at all encouraging for this forum! You guys got something to hide? Or you just don't give a damn? Sorry if I seem a tad aggressive, but this is my car and yes, I'm increasingly disappointed in y'all -- not a mensch among you?

In any case, put the left side up on stands with the LF wheel and down pipe removed. While under, I listened to the transfer case with my head directly under it. Sounds horrible in there at the end of the lash travel -- a combination of steel-to-steel clunk and something that sounds like a piece of tin being tweaked. Wouldn't have thought it could make a sound like that (and yes, it's lubricated). Some kind of bushing issues? Anyway, I expect to take it off the car tomorrow -- first time I've ever fooled with a transfer case, so should be interesting.

If the sounds are comming from the t case area. It defenitly could be one or more issues.
Bad t case, bad output to t case and Probly bad input as well. Or worst case something in the trans. Your at the point where you will have to remove the t case and do some inspecting.

 

[And_44]

Any thing new TrevorS? I'm experiencing same issue on my 1992 TSi. Except my rotation is about .5-.75 an inch before engaging.

FYI 130,000km does convert to about 80,000miles;0D

 

[TrevorS]

Any thing new TrevorS? I'm experiencing same issue on my 1992 TSi. Except my rotation is about .5-.75 an inch before engaging.

FYI 130,000km does convert to about 80,000miles;OD

It may do, but I explicitly specified 130Kmi, not Km. That "i" indicates miles not meters.

I determined most of my problem was due to gear oil choice. I was running too thin oil in both transmission (center diff clunk) and transfer case, changing those oils pretty much eliminated their noises, however, I do still have the rear diff clunk. As was suggested above, guess I'm just going to have to open the differential and measure the backlash. I remember hearing it occasionally in slow speed heavy traffic when starting forward on light changes when the car was new -- it's always been there, though I think I hear it more often now. Especially audible with the windows down.

The amount of rotation you mention isn't encouraging, but at least it's nice to know somebody else actually recognizes what I'm talking about !

 

[And_44]

Ahh, yes. Going to be doing a full Redline fluid change in the next few weeks, hope that will absorb some of the sound of the clunking. But as for the movement, it's discouraging if there is a problem and have no idea what causes it.

If it has always been there but wasn't audible because of the newer fluid in it then it's understandable. Course my driver side rear axle is leaking at the diff so may need to be opened and checked or just upgraded to the 4 bolt.

I wouldn't think there'd be any bad effects from this movement besides it just getting worse and to a certain point where a hard launch with it on opposite of it's movement giving it enough momentum to slam and cause impact damage.

Thanks for the quick response TrevorS and I apologize about the distance thing. Assumed it was Km. Mine is at about 122,000 miles so maybe it is related to mileage. Though as I recall I had a 1990 all original drivetrain with 220,000miles and had no movement what so ever. AND had a leaky seal on transfer case.

 

[kchaazz]

Regarding fluids, select the appropriate weights, then: GL4 in the trans, and GL5 in the t case and rear, but NEVER GL4- 5 in the tcase and rear, according to TRE's info.
Regarding backlash on the rear diff, you can put the rear wheels in the air, lock in the ebrake, then use whiteout to draw a straight line from the pinion flange to the case, then, rotate the driveshaft as far as you can, and mark the case where the mark on the pinion flange is sitting. Measure the distance between the first mark on the case and the second mark, and I believe its not supposed to exceed 5mm, but Ill have to consult the factory service manual to confirm and get back to you.

 

[TrevorS]

Ahh, yes. Going to be doing a full Redline fluid change in the next few weeks, hope that will absorb some of the sound of the clunking. But as for the movement, it's discouraging if there is a problem and have no idea what causes it.

If it has always been there but wasn't audible because of the newer fluid in it then it's understandable. Course my driver side rear axle is leaking at the diff so may need to be opened and checked or just upgraded to the 4 bolt.

I wouldn't think there'd be any bad effects from this movement besides it just getting worse and to a certain point where a hard launch with it on opposite of it's movement giving it enough momentum to slam and cause impact damage.

Thanks for the quick response TrevorS and I apologize about the distance thing. Assumed it was Km. Mine is at about 122,000 miles so maybe it is related to mileage. Though as I recall I had a 1990 all original drivetrain with 220,000miles and had no movement what so ever. AND had a leaky seal on transfer case.

Crazy thing to me is that from day one it was audible and for the life of the car to date Mitsubishi people have considered the sound normal -- they smile and nod as in "yeah, they do that". I'm a pretty easy driver and only occasionally dip into the turbo and practically never hard, no launches and no racing of any sort. It was my DD and that was how I drove it, mostly just point A to point B. Maybe whoever was setting up the differentials tended to do a mediocre job? Perhaps something to do with the parts themselves? Perhaps a traditional Monday/Friday laxness in the U.S. plant?

I'm looking at picking up a 4-bolt setup and getting some hands on differential experience. When I get this one off, I'll definitely be taking a close look at it.

Regarding fluids, select the appropriate weights, then: GL4 in the trans, and GL5 in the t case and rear, but NEVER GL4- 5 in the tcase and rear, according to TRE's info.
Regarding backlash on the rear diff, you can put the rear wheels in the air, lock in the ebrake, then use whiteout to draw a straight line from the pinion flange to the case, then, rotate the driveshaft as far as you can, and mark the case where the mark on the pinion flange is sitting. Measure the distance between the first mark on the case and the second mark, and I believe its not supposed to exceed 5mm, but Ill have to consult the factory service manual to confirm and get back to you.

I was hoping to find such a spec in my '90 Service Manual (two volume set, second being electrical), but only found shim setup info using dial pointer ring gear measurements and contact patch analysis. If you do have a spec for shaft rotation at the differential, that would be great!

 

[kchaazz]

The manual Ive got access to at home does indeed have the shaft rotation spec in it. I will look it up when I get home and post the info for you. Sorry about the wait, I wasnt home all weekend, but Im getting ready to prep my transmission guts for the new build so Ill be in the shop tonight for sure, and if my cell camera will cooperate, maybe Ill just snap a picture of the page and post that.

And one more thing I will make mention of is that it is possible that the splined section of the t case, where the output shaft of the transmission goes in can be literally cracked, which will allow your output shaft to jump within the splined sleeve when initially accelerating and decelerating, and god knows how bad during full boost pulls. Between myself and my roommate, weve got 12 or so tcases, and only one happens to have this issue and was clunking in the previous owner's car, and I have never seen this before so Id say it is rare. It is somewhat troublesome to check for this because youve got to pull the tcase, then remove the seal to notice the crack, so Id definitely go for checking the backlash on the rear end first, since its so simple once we have the information posted.

Alrighty. Ive got the manual in front of me and the instructions for checking the rear backlash are as follows. First put it in neutral. Then set the ebrake and jack her up. Then you are to rotate the driveshaft clockwise as far as it will go and put a mark onto the companion flange and case while holding the driveshaft in position. Finally you are to rotate the driveshaft counterclockwise and mark the case where the mark on the companion flange ends up. Then you measure the space between the first mark on the case and where the mark on the companion flange is now and the limit is 5mm between the two marks . If the backlash exeeds the limit you need to remove the diff and reset the backlash. If you end up needing to reset the backlash my manual covers that too.

 

[TrevorS]

Thanks Dude, that's great -- I pasted that paragraph into my notes !

 

[TurboAnything]

It is very common for the output shaft splines from the trans to the t-case to wear and cause slop in the drive train.

 

[TrevorS]

It is very common for the output shaft splines from the trans to the t-case to wear and cause slop in the drive train.

Maybe true, but I'm manually rotating the shaft adjacent the rear differential, not the transfer case (though I've rotated there too ).