Bent pinion flange R-180

[johnbell47]

I have hunted this problem for over a year, did all the things that you do, U joint angles, balance the shaft, twice, etc. etc. I found the vibration by putting the car up on six jack stands, taking off the wheels and firing that baybie up, 5th gear, idle screw set to 80 mph,(this is when the vibration gets really bad) then crawling under with a stethoscope. when I touched the nose of the diff it liked to have knocked the ears off my head! this pretty much isolated the vibe to that area. The dial indicator told the rest of the story, I figured the pinion shaft was bent, as the indicator on the flange indicated twenty thousands out, but when I removed the flange and put the indicator on the shaft, it was perfect. that's when we went to the drive shaft shop, chucked it up in a lathe and checked the runout. it is thirty at the front of the flange and was in fact 20 where I checked it. So, the machinist verified what I had found. How did the flange get bent, I don't know. It was bent when I bought the car I guess. Could be the 400 horse 350 and a hard launch, could have been a U joint turned loose 30 years ago and banged the dang thing, I just don't know. There has been a lot of speculation among those that have looked at it, but nothing that I definitive.

[johnbell47]

One thing I wondered about that you might answer. The Nissan flange is difficult to find, the Subie flange is out there all over the place, My drive shaft is 1310 U joints with an adapter to the Nissan flange. there is probably an adapter from the 1310 joint to the subie flange available, but I wonder, would the late model subie flange fit the old Datsun pinion shaft? The Subie flange looks to be a lot stouter!

[beermanpete]

We were able to swap the companion flange from our 73 240Z R180 to a 2006 Subaru STi R180 without any issue. Based soley on this I will yes, you should be able to use a Subaru flange.

Edited June 25, 2013 by beermanpete

[johnbell47]

Is the spline count on the axles, the same? Is it possible to just buy a 2004 Subi rear and bolt it up? I hate to be so stupid by my brain is swimming with all the info out there. I have, basically a street machine, it is a boulevard cruiser, So I am interested in reliability, I have a tuned down 350 which is plenty of power for me, air conditioning, lots of sound dreading material, quiet exhaust, etc. What I want to know is can I actually swap out a diff that is 30 years newer, get a gear ratio that works better with my T-5 overdrive transmission for a hell of a lot less money? really?

[Captain_Zeros]

Nope, axle splines are different. It's a damn shame.

Beta Motorsports makes a stub axle with subaru splines though, looks like wolf creek is selling them now. $500, but I guess that's still probably cheaper than hunting down an OS Giken LSD.

Tranny & Rear Diff Parts

Edit: Or you can have custom axles made.

[johnbell47]

I finally fixed the vibration. I was unable to find just a pinion flange and had to buy a complete 3rd member. I changed the flange, didn't fix the vibration, then I noticed that the driveshaft had the paint worn off the slip flange about 1/2 inch rearward from where it goes into the transmission, then I got to looking and the moustache bar was in contact with the down braces for the rear of the A arms. I had built a Ron Tyler mount according to the specs that I got I know not where, but the dang thing moved the 3rd member back. I put the factory mount back on and reworked the Tyler mount to be just a snubber to prevent the front of the diff from moving. Basically I sandwiched the diff between the factory mount and a modified GM transmission mount, I shaved about 3/4 inch off the G.M. Mount eliminating the single bolt on top. now we just have a rubber block with a two bolt mounting flange, I compressed this about 1/8 inch with the front crossmember. That moved the vibration rearward. I did not have the half shafts on so it had to be the rear end. I took a chance and mounted the junk rear end that I had bought to get its flange and that was the problem. No more vibration. I cannot see anything in the bad rear that would make it vibrate, but there is something wrong in there. this car is smooth as silk up to 95. It has never been right, but I just did not know what "right" was. With the Hushmat, quiet mufflers, mild 350 chev, stock rubber suspention all new. new KyB struts, air conditioning that works pretty good, all new rubber window and door seals, Mid line Sony sound with component speakers and Lexus Mirrors,Honda wiper motor with working washers, working rear window heater, flashers, seat belt warning chime, etc. I believe this baby is ready to drive just about anywhere in comfort.

[Patcon]

Good for you Pictures please...

They always help keep me motivated.

Charles

[johnbell47]

Did not take a single pic. I was too determined, to greasy and too worried to even think about it, but next time I jack it up I will take a pic of the front differential mount set up. That's about the only thing that is different than stock.