Rear end and driveshaft woes

[wingwalker]

I bought a partially done project--a relatively rust-free 280Z with what appears to be a rebuilt Vortec V-8. Those are the good things I can say. This car had once had another engine in it, the hood had a cutout section where there may have been a blower sticking through, and in the glove box were several drag-strip timing sheets in the 12s (so if there was a supercharger, on it it wasn't all that effective). The seller said that the original engine blew, someone bought it and was installing this engine and then ran out of steam. She bought it and thought her boyfriend could finish it, but from what it appears, he just had her order some expensive parts, including a new aluminum radiator, new Holley 650 carb, new fuel pump and a few other things.

 

I've had to redo most of the boyfriend's efforts, and in other posts, you may have seen the issues I've faced.

 

I am using a different motor-mounts and  tranny--a rebuilt GMC 2004R--so the engine sets back. Therefore I had to pull the driveshaft and have it cut down. If fits, but doesn't properly mate with the differential. I've spent three long afternoons under the car, trying to get the companion flange on the driveshaft to properly mate with the flange on the diffy. Never could get the flange to drop in so that the two faces mated. And this is the flange I took off it, the flange that the dragster owner had in place. I'm certain that the machine shop didn't somehow swap out that part, because I marked one corner with a center-punch so I'd mate it as it had been.

 

Finally in exasperation today, I pulled the shaft out for the millionth time and measured the male flange, then went under the car and measured the female cut-out. I was stunned!

 

The driveshaft flange is 157+mm and the machined slot on the flange on the front of the differential is 49mm and change--they never mated! Must have been a vibrating ride--wild and noisy.

 

So, this tells me that the flange is for a different rear end than mine. I am going to include photos with this of the flanges in question and of the differential. I think I read on this forum that a smooth rear cover might indicate it is a  R200 rather than an R180. So, the questions are:

 

1. Can I swap out either the flange on the driveshaft or differential? And if so, which? The flange on the U-joint would be easiest. And I am not taking this to the strip, so it doesn't need to be the most robust. 

2. Can you tell from the photos which diffy I have back there?

 

There's the driveshaft--local shop did a nice job cutting it down

Here's the flange on the U-joint. If that can be traded out with one that fits the diffy, it would be easiest.

 

Here's the flange on the front of the differential. That machined well is only 49mm and change.

If this is the flange that needs changing, do I need a puller?

 

Here's a side view of the differential and below is a shot from the rear. Can you tell me which it is?

 

Thank you in advance for the answers.

 

Edited June 12, 2020 by wingwalker

[NewZed]

What years 280Z?  The 75 280Z's had R200's with the same pattern as the later 300ZX's (I thought..).  They were oddballs.  Check your driveshaft u-joints to see if they are removable, look for the internal clips.  280Z's had staked u-joints, not replaceable without machining.

 

Here's some part numbers from an old thread, below.  I'm not sure what's what in the thread, I thought that the 75 280Z parts would fit the 300ZX diffs.  Not sure which if these is which, but it shows where your problem probably started.  You'll have to do some more searching and checking of your parts.

 

https://forums.hybridz.org/topic/113866-280z-r200-differential-pinion-flange-wanted/

[NewZed]

This might help.

 

https://shell7.tdl.com/~jags/Pages/Parts_DAT_driveshaft_flange.html

[wingwalker]

New Zed,

Thank you. Both links are very helpful. Looks like I need the DAT110 flange, but before I order it I need to go back under the car (for the million and first time) to take careful measurements to ensure it is what I need.

 

My 280Z is a '77 built with auto transmission. The u-joint does disassemble with clips, so it may be the converted Chevy part per the JTR manual. Your first link shows that the flange is on a spline, so I doubt it'll need a puller. And that's good. But nothing is simple.

 

I have the rear drums and brake parts off, so I won't be able to set the handbrake to hold that shaft steady when I go to take the big nut loose. So, I need to finish rebuilding the brakes before I can fix this driveshaft issue. I've ordered a liter of brake fluid that won't be here until Monday evening. I want to use it to flush the lines before putting new hoses and brake cylinders on it. Every step hinges on another, Nothing is simple.

 

Can anyone ID that differential?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[NewZed]

The R180's have axle holes surrounded by five bolts.  The R200's don't.  For some reason I can't figure out the side view that you showed, the axles are in shadow.

 

Also the R200's have a rectangular chunk of aluminum on the bottom of the diff cover.  Your second picture seems to show it but it would be upside down.  Can't see the drain plug to know what's up or down.

 

It looks like an R200 but those are bad pictures.

 

 

[Miles]

delete

Edited June 12, 2020 by Miles

[Twisted46]

That looks like the R200 case in my car. The problem with project cars is you never know what you will find and people do some pretty hair brained stuff. On top of that I have learned that Datsun did a lot running changes in those years (my 74 is a mixed bag of what "should" be on there and it was all original when I bought it save for some fuel and brake lines. If you want to be extra sure and not have to reorder parts then pull the diff and measure the ring gear. 

[wingwalker]

Thanks,

I'll go out and inspect the differential more closely--sounds as if the bolts around the axle holes are the clue. And I need to make some careful measurements to ensure that part is the one I need.

Always a challenge working on these old things--especially when some PO had creative engineering notions.

 

[Miles]

Do you have the JTR Datsun V8 conversion manual?  It covers all of the issues you are having.

[NewZed]

That "shell7" link I placed above is a page of the JTR web site.

 

https://jagsthatrun.com/collections/datsun-z-parts

[wingwalker]

Great help, everyone. Thanks.

 

I measured carefully and then spoke on the phone with someone at JTR. It is the DAT 110-2 flange I need.

 

So, another $85.00 into this never-ending project, and I should have the driveshaft and differential properly mated.The man at JTR said they have it on hand, so it should ship on Saturday. With new brakes on all four corners, that should take care of the moving parts needed to move this thing down the road.

 

A close look at the differential reveals no bolts around the axle holes and a rectangular bar across the bottom of the cover. I hope the ratio will be good for highway driving. My transmission, a GMC 2004R, has a decent overdrive ratio in fourth--so I'm not worried. What I want out of this is a nice highway cruiser with pep.

 

I still can't get over discovering that a previous owner ran this car on the quarter-mile, running fast, with only bolts in shear holding the driveshaft onto it. Ignorance is bliss, I guess.

 

I want to get this thing on the road, then I can go back and pull stuff such as the differential, refurbishing what needs it, and cleaning up and detailing as I go along.

 

I have welded patch panels into all the holes and indentations on the rear, so a day or so of body filler, sanding, priming, more filler, more primer, block-sanding and lots of dust  lies ahead. Then I'll bolt the gas-tank in after all that mess is finished. I was happy to find that the tank was clean and rust-free. It was in the trunk of the car when I hauled it home, so I expected the worst. I pulled the sender and used a flashlight and mirror to see as much as I could, and was pleased. It's painted, and I have new strap-liners, so that should be an okay project.  Next big issue will be the a/c installation. It looks like a lot of work, but all of it appears straight-forward. I have the dash out, so that will help.

 

Thanks again everyone.

 

[ritrebor]

77 280z with auto came with a R180.

Manual came with a R200

So probably it's been swapped.

 

ritrebor

[wingwalker]

The proper U-joint flange from JTR (the DAT-110-2 flange version) arrived in the mail--a nice piece, and I swapped it out for the improper one the previous owner had on it. Mated perfectly without any drama whatsoever. Tightening the four bolts that hold the flange to the differential is tedious, with two open-end wrenches achieving about a 1/16th turn at a time, but it's in . I finished rebuilding the brakes yesterday with the help of my son (who drove over from the Seattle area, about five hours from here). Wonderful father's day gift--two masked men getting grimy doing brakes on a car precisely as old as my son.  When we flushed the brakes, we used up almost a liter of fluid until we achieved clear stuff--it was nasty stuff. Glad I replaced the master, the calipers and rear brake cylinders, along with flex hoses. Should be a tidy-clean system now.

 

Miles, you asked if I have a JTR manual. I do, and it has been a great help. But on the drive-shaft issue I didn't refer to it, since all I was doing was putting a part I had taken off back on. I am still astounded that that the previous owner was driving and racing with a driveshaft improperly mated and fastened. It depended on nothing more than the shearing strength of the four bolts--not the strongest way to use a bolt. Also, the flange had to have been misaligned. Must have vibrated like crazy! But thanks for the reminded; I plan on going to the manual as soon as something seems amiss--even if the P.O. had been using it that way!

[Miles]

2 hours ago, wingwalker said:

The proper U-joint flange from JTR (the DAT-110-2 flange version) arrived in the mail--a nice piece, and I swapped it out for the improper one the previous owner had on it. Mated perfectly without any drama whatsoever. Tightening the four bolts that hold the flange to the differential is tedious, with two open-end wrenches achieving about a 1/16th turn at a time, but it's in . I finished rebuilding the brakes yesterday with the help of my son (who drove over from the Seattle area, about five hours from here). Wonderful father's day gift--two masked men getting grimy doing brakes on a car precisely as old as my son.  When we flushed the brakes, we used up almost a liter of fluid until we achieved clear stuff--it was nasty stuff. Glad I replaced the master, the calipers and rear brake cylinders, along with flex hoses. Should be a tidy-clean system now.

 

Miles, you asked if I have a JTR manual. I do, and it has been a great help. But on the drive-shaft issue I didn't refer to it, since all I was doing was putting a part I had taken off back on. I am still astounded that that the previous owner was driving and racing with a driveshaft improperly mated and fastened. It depended on nothing more than the shearing strength of the four bolts--not the strongest way to use a bolt. Also, the flange had to have been misaligned. Must have vibrated like crazy! But thanks for the reminded; I plan on going to the manual as soon as something seems amiss--even if the P.O. had been using it that way!

 

My first 72 240Z was a father and son project. It was an old SBC v8 conversion that was badly done. There were so many conversion/mechanical/electrical  issues with the car that we pulled it completely apart. It was worth the effort though. So I bought another 72 240Z and did the V8 conversion. The car had a severe vibration around 70mph. I ended up pulling the drive shaft and took it to a different shop. The shop discovered that the previous shop had welded the shaft off-axis after they cut it. The shop re-cut/welded and balanced the shaft. No more vibration.

 

The JTR manual is not perfect. Over the years I have found mistakes in the manual, but is does get you off to a good start.

 

Glad you found the vibration. A drive line vibration  can make it impossible to enjoy a z car.

 

Mine is down due to a carb (Holley) issue and a leaking 240sx rear caliper. Got ten years out of that caliper (Nugeon)