My 1200 has had a bit of a shudder over 40mph. The shudder grew to a shake to today when I was trying out my weber. I had initially thought the wheel alignment was out at the back but after today I'm pretty sure I'm in the market for a new diff.

How available are are new centres?
Should I just got for the h150?

just lock it :)

is it 100% definitely the diff? No chance it is a stuffed uni on the tailshaft? (typically diffs whine rather than shudder, about the only exception is with two seriously mismatched tyres on the rear causing the diff centre t have to considerably compensate, generally if the wheels are within a few % of each other it has no trouble, but beyond that, well the cross pin is a 'bushing' with the spider and end gears, they aren't needle roller bearinged or anything, and they can get stressed if they have to massively move/spin/rotate to compensate for greatly different axle speeds from different sized wheels/tyres)

Jmac: you might be on the money with the uni joints. The clunking and shaking could definitely be caused by play in the joints. That's good to, I would much rather take the drive shaft to get refresh(?) than replace my centre/rear axle.

Can uni joints be done by an amateur or will it require professional machinery and skills?

Datsun 1200 u-joints are non-replaceable except for early units.

Take it to the pro's if you don't know how. it's not something that gives a lot of prob. If it was shaking at 40mph and then stoped at say 60mph my money is on the drive shaft too. But remember to check the seal on the tailpice of the gearbox too. The shaking can damade it or even brack it, hope you can sort it!!

If the uni joints are non repairable as such, there is surely a workaround, even if it required different flanges on the tailshaft to be welded in, and a uni joint with the right diameter cups, but able to be locked in place used in there. In other words it could be more expensive, but there'd have to be a workaround.

On the topic Kiri1 mentioned - I absolutely agree. A few years back, friends of the family had a bluebird (owned since new). It ended up seizing a uni. It was still 'driveable' but would shudder at anything above 50km/h. Being that I used to work on cars for a living, I offered to fix it for the cost of the uni, no probs. Instead of that, they took the attitude of 'i'll just drive it slowly and it'll be allright' and left it. It ended up tearing up the extension housing bush, then eventuaally bearings inside the box, as the ooutput shaft could 'flop about' as the tailshaft span. That $20 uni joint ended up costng them the gearbox (they actually paid to have it reco'd but it seemingly did something to either the output shaft or the bearings between it and the mainshaft, as it was still (relatively) sloppy thereafter and ended up vibrating again. All for a $20 part.

If you were in melbourne (and if they are still there, haven't been past in a while) then I'd suggest 'univeral driveshafts' near the lost dogs home in north melbourne (I'm not 100% but think it is gracie street. Not necessarily the cheapest guys in the world, but reliable and consistent with their work in my experience.

I haven't (so far!) had to replace the unis on my datsun coupe, so I haven't had a massively close look at them, but coming from a general revheead background, custom tailshafts and/or different flanges being welded on to each end, to enable things like a supra box behind a holden engine, going to a ford 9" diff, such work is commonplace. Surely there is a solution out there for datto 1200 enthusiasts?

Read a bit about u-joints.

http://checkerauto.com/Maintenance/MaintenanceDriveShaft.aspx

And a bit about replacement.

http://www.automedia.com/U_Joints_-_I ... al_Joints/res20010201uj/1

Although it is an important job if you take your time and pay attention to detail, even a first-time job can come out with good results.