Diff issue, vibration, several questions

[Zed Head]

Your first description sounds like bad u-joints, in the half-shafts or propeller shaft. Maybe they didn't get them centered correctly or bent a yoke. Horrendous at acceleration implies low speed, lots of torque through the shafts.

Could also be something simple like a bad wheel bearing. You really aren't giving enough information though, guesses about vibration can go on forever. Still don't know what bushings you actually replaced. Good luck.

[Diseazd]

I will pull consider pulling the shafts and drive shaft and see what they balance out like. When I say pro, I mean guys who do nothing but drive shaft stuff all day long. I have sent them a ton of business over the years and they are really good, but everyone makes mistakes. I may pull the shaft out of the donor car and put it in, are the auto and 4 speed the same drive shaft?

Yes.....But your early Z has the short drive shaft......so you'll need another early Z manual or auto driveshaft. Why not try the spacers first.....a lot easier to eliminate alignment of the driveshaft ends first. If someone removed the mount without replacing the spacer, that could easily be your problem. BTW....beautiful car! PS.....make sure the PO didn't already move the diff rearward.....in that case you would need the 72-73 longer driveshaft.

Edited February 20, 2014 by Diseazd

[jmortensen]

FWIW I have an early driveshaft with new U-joints, which I bought and then decided to go the V8 route. $50 shipped if you're interested.

[Richard Oben]

Zed Head, everything has been rebuilt or replaced. I took it all the way to the tub, new wheel bearings, new half shaft U joints, new prop shaft U joints, everything. I am not sure what more info you want. Ask and I will try to be more specific about what was done or not done.

I have an early shaft in the parts car so that will be cheap and easy.

To be clear it is not a low speed vibration, it is applied throttle above 60 MPH, not low speed. Wheel speed and shaft speed are a good thought, it does sound like wheel speed more than prop speed. It rained last night so I may move the car around and get it on the lift and check the things listed. Thanks for all the thoughts. Hundreds of heads are better than one. Richard.

[madkaw]

Motor mounts and tranny mount condition?

[Richard Oben]

Everything new, motor mounts tranny mount all new. I basically saved the tub and if it was available new I bought it, if not I rebuilt it. New torque converter, new mounts new bushings new, new, new. Now I fully understand that new may not mean good but. If it moved or supported something that did move I replaced it. Every piece of weather strip, gasket, bushing, mount. I kept the rubber on the mustache bar and the rubber for the Motor and Trans mounts but did urethane for the all the suspension stuff.

I just can not get past the 60 to 65 MPH and applied throttle only part and the fact the diff swap virtually fixed it. I am going to dig it out since the rain moved all the ice and get a look at it today. Richard.

[Zed Head]

The 60 to 65 mph news is a good fact. Everything from wheels to driveshaft increase RPM proportionally to road speed. The "horrenodus" part of your earlier description also sounds like a high inertia object, wither heavy or large range of motion. The driveshaft or a wheel both fit.

jmortensen's price on that driveshaft is a good one, and they're hard to find. Plus he used to be a part of a company that did driveline work, M2 Differentials, so the work on the driveshaft is probably right. You might pick that up and try it. $50 for a spare part and a cheap diagnostic tool.

You might also swap your spare tire for each of the four to see if one of them has an effect. Did you remove the rear wheels when you replaced the diff? Maybe one of the wheels is bent and ended up in a new spot.

[Richard Oben]

I drove it Friday and before I do anything else I am going to have the tires balanced. I had a steering wheel vibration too. Working down the list. I have a series one shaft so I do not need two spares. Thanks for the all the ideas. Richard.

[Mark Maras]

Looking back at your original description of the problem, I've never had a vibration that was horrendous or changed with applied power except the front of the drive shaft. Slack in the rear of the drive shaft will give you clunks but not a horrendous vibration. Here's my suggestion- With the car safely secured in the air, trans in neutral, hand brake off, crawl under the car, grab the drive shaft near the front yoke and push, pull and twist in all directions and try to see any movement then rotate it and do it again. There should be NO MOVEMENT except rotational. It only takes a few thousanths of an inch to give you a terrible vibration that will change with power application. Other possibilities-the u-joints that were installed will not balance. The front yoke was damaged during u-joint installation or not installed in the same position in relation to the drive shaft. The old c-clip was used on the new u-joint. The drive shaft is bent.Another club member, a while back, said that he had found a problem with the out-put shaft in the rear of his automatic. By your description this doesn't sound like it is relatable to wheel speed. I've had some severe wheel vibrations but they pale in comparison to drive shaft vibrations because the drive shaft turns about 4 times faster than the wheels and axles.

Mark in Portland

[djwarner]

Re-reading your posts, it reminds me of an issue I had with a '70 510 wagon automatic that I purchased new. I had waited for the Japanese mfg'd automatics to arrive because the Borg-Warner AT Datsun had been using didn't have a very good reputation for reliability. With 11,950+ miles on a 12,000 mile warrantee, I was driving across I10 at 70 MPH when I heard a sudden loud bang followed by a bad vibration. Stopped at a garage where we pulled off the drive shaft and found the rear transmission seal was torn and a half moon shaped chip had worn off the aft end of the sleeve bearing at the end of the rear shaft housing.

The chip had lodged between the bearing and the spline spinning the bearing in the aluminum housing. The housing was ruined as the eccentric bearing/shaft spline vibrated. It turned out the transmission, being new, had no spare parts in the US. We pulled out the chip and put things back together and I found that if I got the car up to 65 and eased my foot of the gas, the vibration would stop until the speed dropped to under 45. I ended up driving the car 1,000 miles that way until it gave up the ghost in Dallas. Datsun ended up pulling parts from a dealer demo car to get me back on the road.

In my case, the drive shaft was perfect, but the rear transmission housing and sleeve bearings were shot. As Mark said, If you jack the car up and get any play at the front of the drive shaft, that is probably your source of vibration. However, the problem may be in the rear housing - the only part of the car you haven't messed with yet.

[Richard Oben]

What gets me is the fact that changing the diff to another used one virtually fixed it. Maybe the front bearing in the diff was bad enough that it could not take a load.

[jmortensen]

jmortensen's price on that driveshaft is a good one, and they're hard to find. Plus he used to be a part of a company that did driveline work, M2 Differentials, so the work on the driveshaft is probably right. You might pick that up and try it. $50 for a spare part and a cheap diagnostic tool.

Just to clarify, my company sold driveline parts, we didn't do driveline work. But that shaft came from preith, who built it for use in his race car but never used it.