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looking for experience/wisdom 71 240z driveline issue


Triumph26

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Hi guys, first let me say that my Z is not at my house.  It's at the shop, so I can't actually look at it right now.  But this issue has me up at 3:30 AM (to be fair I got off work at 2) and I'm looking for some thoughts on an issue the car has.  Without getting too wordy, I inherited this car when my dad passed away last November.  I just got it home to OR (towed from PA on a trailer).  I drove it a bit while in PA, and it ran and drove great except for a vibration in the rear end above about 50 MPH, which seemed to get better over 70 but didn't go away.  I know my dad was trying to solve this issue, (I have records from when he bought in new in December of 1970-although the car is a 71).  He had a bunch of u joints replaced over the years, but the vibration issue seems to have started around '04. He had the inner u joints on the rear axle replaced and the issue was better but not solved.  I've searched this site and some others but haven't really found an answer.  I'm aware there's a lot going on in the rear end of the car that could cause a vibration and I'm not looking for diagnosis right now so much as anyone who has had this happen and how they solved it.  When I was driving it in PA it started a pretty loud popping noise at all speeds definitely coming from the rear driver's side.  I figured it was a u joint or perhaps wheel bearing.  When I got the car to OR I took it to my local mechanic who I trust, but he works on everything from farm tractors to Subarus and has zero experience with these cars.  He replaced both u joints on the driver side rear axle as well as both driver's side wheel bearings.  I drove the car literally 20 miles before the same popping sound started again, although I thought it was from the passenger side.  I figured the other side went and I'd buy the parts and do it myself this time, but the next time I drove the car the water pump died.  I replaced it this past Tues, and barely got the car out of my driveway before the rear driver's side outer u joint literally grenaded.  Luckily no damage except to the joint, and I had it towed back to the mechanic.  He replaced it free, thinks he damaged one of the clips installing it.  Good guy, felt like crap about the situation.  He called me today and said that when he replaced the driver's side joints the first time all the others seemed tight, but now they seem loose.  He asked if I wanted him to just replace them all, his theory being that the car may have sat too long and all the grease is super dry.  I do know that the car was driven very infrequently over the last ten years, maybe a few hundred miles a year.  

 

My brother says he read that the first gen 240s had a known issue where the driveline was too short and they went through u joints like crazy.  Datsun had the issue solved by 1971.  This sorta jibes with the records I found of what my dad had done.  I don't think the vibration is tranny related due to it occurring at a certain speed.  It had a new tranny installed in the late 80s when the first one got stuck in 4th.  Dad had it rebuilt but it did it again.  He contemplated having a later model 5 speed installed but was always a stickler for cars being original and had a 4 speed put in.    

 

I just realized how long this is, so I'll try to shut up.  Can anyone confirm or debunk that the early 240s had a known driveline issue?  I want to drive the car and am not a stickler for originality, I'd upgrade to a 5 speed if it works better.  Any thoughts on the u joints going frequently?  I trust my mechanic, but any thoughts on his theory of old dry grease being the culprit?  I know that I will continue to have small issues to deal with due to the car sitting, but I want to drive the thing!  Any thoughts are appreciated.  I'm hoping to get the car back all good to go, but given the fact that my dad was having trouble solving the vibration issue I am not all that hopeful new joints all around will be the silver bullet.  Thanks!

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I'll check but I don't think the driveshaft length changed from 240 to 260 to 280. There was an early 71A 4 speed that was replaced by the 71B in '71 ish. That's about it. Didn't you say it had low mileage? Maybe a bent rim or wheel weight fell off. Maybe the tire is damaged. Tires are better made and balanced today.

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It's a good point.  It's got about 66k on it.  The tires are in good shape but pretty old.  A rubber upgrade would be a sensible expenditure.  I stopped by today to visit the Z at my mechanic's shop and was able to look at it while up on the lift.  There was definitely slop in the joint from the differential into the axle shaft on the passenger side that was bad enough to cause the vibration on its own.  I'm also having him replace the diff and transmission fluid, as I can't find a record of when that was done last.  A lot of the old records I have are handwritten with minimal info and just a cost.  Thanks for the info. 

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I got the car back today from my mechanic.  He replaced the other three u joints on the half shaft/axles, and the rear one on the driveline.  It's pretty clear to me that the differential was never moved back.  It's something I'd like to do, but I'm not really sure how to go about it.  my mechanic says that the driveline is pretty shot, and he had trouble getting the joints to fit securely.  He also thinks it's bent a little bit.  He tightened all the bolts on the 2 piece rims as well.  I didn't even know they were two piece rims.  End result it that I drove the car today and it had almost no vibration.  

 

I want to replace the driveline, but I'm not sure if I should just replace it with the same (early) 240 or?  Any input is appreciated.  Additionally, I'm going to be looking into new wheels.  The original EMPI magnesium wheels are cool, but I want to put a more modern wheel on the car along with new tires.  

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Glad to hear you've got her back and driving well.

 

Now, just slow down Grasshopper!  

 

Drive her a bit before doing anything (unless the old tires are dry rotted or cracked).  After a few hundred miles, you may be perfectly happy.  Just make sure the rubber brake hoses on all four corners are good.

 

EMPI wheels from the 70's are two-piece?  Who knew????

 

If by "driveline" you are referring to what we Americans call the "drive shaft", Datsun calls it the "propeller shaft". 

 

See the FSM pages PD2 & PD3 for details and troubleshooting.

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Good advice dgi. The tires are servicable, but at least ten years old. The brakes were rebuilt in 2012, and are good. Yes, the "propeller shaft" is what is at issue. The vibration that I'd felt before is all but gone. I can feel it most under somewhat hard acceleration in 2nd. Next project is an oil change and greasing every fitting I can find.

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