Hello everyone. I have a 1970 240Z with a 78 tranny and a 82 rearend. I have a whirring sound that increases as I accelerate, and goes away when the clutch is in or I am in neutral. I don't know if it is a rearend problem or a tranny problem. If you all could help me troubleshoot, it would be greatly appreciated. Thank you all, Rick.

It could be the clutch t/o bearing, transmission, or rear end. If the sound goes away when the clutch is disengaged I'd suspect the t/o bearing first, but someone is going to need to listen to each component while the car operating (in gear) on a lift to attempt to determine by ear where the sound is coming from.

The whirring sound is definately gear derived. I cannot figure out if it is the tranny or the rearend. The sound is only apparent when a load is present. Hopefully this info will help. Rick.

Change the tranny and diff lube then see if you still have the noise. Check the drained fluid for metal bits.

Chris

You're most likely losing a countershaft bearing. It's not uncommon after 60K miles. Steel in the oil is a good (or bad) indicator. $400.00 or so spent on a refresh (new bearings, seals and as-needed sycros is, in my opinion, money well spent on any transmission your going to use. Most "Real" transmission shops will have no problem navigating a FS5C71B, as there's nothing "new" or "High tech" about them. But, I suggest that, You buy the Nissan kit, and supply it to the mechanic, ensuring that he'll use the right parts.

Victor, you are pretty sure it is the transmission?

Yes, fairly sure. The countershaft bearing sits in the bottom of the case and is usally the first to go.

Corrections to my original post

FS5W71B (W not C, indicating "Warner" style brass sycros)

Nissan offers no "Kit" and building one from Nissan stock would be $$$$.00 . However, they are availible aftermarket at a very resonable price $137.87, part # MRK100600 from Drivetrain.com

BTW, I noticed that your in San Diego. If you take your box to Classic Datsun Motorsports, Les will agent the work to a Nissan Transmission specialist that does work you can have complete cofidence in.

I have, in my garage, an 82 ZX 5 speed with 36,000 miles on it. I was told the 78 is a better tranny so I went with that, but I can put the 82 in. Is there an inexpensive LSD kit I can put in my R200 rearend? Let me know, Rick.