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Happy New Year to you all. 

New Year = New Z problem and I'm hoping someone out there has some wisdom they can share. Sorry for the long post. 

I'm having an issue with my tailshaft where the rear uni joint keeps breaking. Prior to it breaking the first time, it was in the car for 6 years and never had an issue; the tailshaft was made professionally after I did the s13 gearbox conversion. 

After it broke the second time, I started looking at the rest of the driveline and noticed my gearbox mount was stuffed. I had another lying around so I replaced it and then used some chain to stop the gearbox from lifting under acceleration. Drove the car easy and there was no vibration and everything seemed fine. 

Under heavy acceleration, bang, same uni broke. Nursed the car back home and started looking over the whole car. I measured the operating angles between the gearbox and diff and I don't think it's right. Does anyone know what the angles are and what the tolerance is? I've checked online but haven't had much luck yet.

My diff is 4° up, tailshaft is 0.5° up and gearbox is 1.5° up. I'm in the process of modifying the gearbox crossmember to suit a S13 polyurethane mount and I'm trying to work out if I need to shift the gearbox to change the angle? I checked the diff mount and it looks fine. 

The only changes I've done in recent months is coilovers and tyres but that was months ago. I also raised the height of the car slightly to get more ground clearance for a roadworthy so I could get club reg.

Any advice would be greatly appreciated.

Marc.

 

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Are the TS UJ's greasable, Marc?
If so, replace them with Hardy Spicer R-seres units.

I highly doubt it's the TS angle..
 

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Thanks for the reply. They're hardy spicer uni's, no grease nipple. The body of the uni isn't breaking, it's shredding the bearings and breaking the bearing caps.

Edited by my_mad_z

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If it’s shredding bearings then I would suspect angles are the culprit.

Ideally gearbox and diff need to be at the same angle or at least close. The actual angle isn’t really important (no more than 5 preferably) as long as they are the same.

Assume it is a conventional tail shaft with slip joint in the gearbox or is the slip joint in the shaft itself?

Edited by KatoKid

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1 hour ago, KatoKid said:

If it’s shredding bearings then I would suspect angles are the culprit.

Ideally gearbox and diff need to be at the same angle or at least close. The actual angle isn’t really important (no more than 5 preferably) as long as they are the same.

Assume it is a conventional tail shaft with slip joint in the gearbox or is the slip joint in the shaft itself?

I had a chat with Locky and after some discussion, I thought about the diff. The LSD was cooked from the day I got it and after putting clutches in it, it stopped open wheeling. That, along with some stickier tyresmight be causing the issue. When I had the tailshaft redone, the guy said the uni's won't handle more than 300hp, looks like I might need to upgrade the tailshaft. Checking a few more things to see if I can change the angles so the diff/gearbox are parallel. 

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I put RB box in my car and by putting the larger subaru diff flange on my datsun R180 diff I was able to use the complete skyline shaft. These larger skyline unis seem to be able to handle plenty of power. 

I saw your car at a Japanese car show in Melbourne a couple of years ago. I like the wheels on it so much I bought the same. :)

Edited by GregTas

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So I mounted everything back in and I removed the thick washers from the moustache bar as I replaced the original bushes with polyurethane ones; my diff angle is now 3.5° up, tailshaft and gearbox are still the same. I found a good app that helps with driveline angle and it says the setup is out of tolerance. I think I have to change the gearbox angle to try and get it within tolerance. I'm not sure if anyone has measured their angles? If so, and you're happy to share, please let me know. Last thing I want to do is get a beefier tailshaft a s break it cause my angles are wrong. 

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If you can’t lower the nose of the diff or raise the rear anymore then as you point out the only option is to change the gearbox angle.

Are you using the standard diff cross member and mount or an RT type diff mount? May be easier to modify this if so.

Dropping  the gearbox mount will require some decent spacers to get 2 degrees so you may want to look at spacing the engine mounts to raise the nose of the engine as well if you have room?

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7 hours ago, KatoKid said:

If you can’t lower the nose of the diff or raise the rear anymore then as you point out the only option is to change the gearbox angle.

Are you using the standard diff cross member and mount or an RT type diff mount? May be easier to modify this if so.

Dropping  the gearbox mount will require some decent spacers to get 2 degrees so you may want to look at spacing the engine mounts to raise the nose of the engine as well if you have room?

I'm using the R200 longnose setup with a standard mount and cross member; the only difference is the polyurethane bushes in the moustache bar. I can't adjust anything in the diff setup without modification. I wonder if my engine mounts are stuffed, I haven't checked them thoroughly so I'll check that next. Nice idea about raising the engine mounts, if mounts are stuffed that could be the reason why it's out of whack... thanks for the advice!

I've replaced the original gearbox mount using this https://au.gktech.com/polyurethane-gearbox-mount Hopefully I can get the angle I need by spacing the engine/gearbox. 

Marc.

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