Differential noise

[Mark E.]

Re: Differential noise

AFAIK they're all the same for any clutch type LSD - GM, Ford, Mercedes, BMW... The NAPA part number for a 4 oz. bottle is NCB 4285V.

Duke

Good to know. Years ago, a GM mechanic advised to stay with the GM product... but maybe that's not necessary.

[Duke W.]

Re: Differential noise

GL-4 didn't exist in the fifties and sixties. Neither did GL-1, 2, 3, 5, or 6.

"Gear oil" back then that was used in virtually ALL manual transmissions and axles in domestic cars was, as I said, a product that conformed to the Mil-L-2105 miltary specification. I recall the last suffix was D. The milspec was cancelled and replaced with the commercial SAE 80W-90 GL-5 API spec around the early to mid-seventies.

Most modern manual transmissions and sidewinder transaxles (that have a helical not hypoid final drive gearset) recommend 75W-90 GL-4 or ATF, most of which are a 70W-75 SAE viscosity grade.

There's lots of internet "advice" to use GL-4 in a vintage manual transmission. but I still recommend GL-5. I have never seen a rigorous durability test of GL-4 versus GL-5. Have you? Also the "yellow metal corrosion" myth has been promulgated for decades by "boutique" oil blenders whose products for the most part are not API certified. I've talked to guys that have overhauled countless vintage manual transmissions. Did they ever find synchronizer issues. Yes, wear. Corrosion, not a one.

Thanks for pointing out the error in the additive size. I corrected it to 4 oz.

Duke

[Frank E.]

Re: Differential noise

Thanks Duke.....

👍👍

[Jack J.]

Re: Differential noise

LATEST UPDATE: Yesterday Morning I went to the shop where they were going to drill and tap, drain and refill my differential. I told the mechanic/tech that next Tuesday’s appointment honestly, was not possible. Rather than attempt to reschedule, I told him that I’ll just purchase the oil, additive and plug he had previously placed in a box Thursday, and that I may or may not drill & tap myself, depending. He told me down the street was a Harbor Freight where I could purchase a transfer pump, which is what I did and I spent an amazing “ON SALE” $5.00 for one. I DID NOT drill and tap. My first posi drain and refill was a piece of cake. Drove it today and the noise is GONE. However, I must say his earlier diagnosis of also checking the posi’s front snubber’s bolt for tightness was correct because I was able to get some movement on it. So possibly, a combination of the 2 part diagnose was the probable cause of the squeaking noise. As a footnote, the first added, 2 bottles of 3.6 OZ additive were labeled as such, “FORD PERFORMANCE PARTS”. Now gentlemen, steer me in the right direction for a “NEW” clutch assembly appropriate for a 365 plus HP with a 3:36 rear end, of which I just love in first gear! Thanks, Jack J.

[Mark E.]

Re: Differential noise

Jack,

That's great news. Thank you for posting the resolution; I wish more folks would do this so we all can learn.

I never replaced a clutch in a Corvette, but there are some good threads in this forum on this topic.

[Jack J.]

[Terry D.]

Re: Differential noise

As for a clutch you can't hardly beat the Luk oem replacement. They made alot of OEM clutches over the years and performed very well. Your 365hp+ is putting a little over 300 to the rear wheels, a stock LUK will handle that with ease.

[Duke W.]

Re: Differential noise

A Flint-built 327/365 will make about 230 SAE corrected RWHP. Honest SAE gross at the flywheel is in the low 300s.

Clutches are designed to handle torque, not horsepower. The OE small block clutch has about 2300 pounds of clamping force. Big blocks are a bit more. Clamping force data is in the AMA specs.

Duke