Gear whine

[Jim Stanley]

I have recently had a clutch kit put in my car. It runs great with no problem. Both before and after the trans was pulled there was a gear whine. It is most noticeable when letting off the throttle in higher gears. Note: The trans oil was changed using 10w60 Castrol. The shop is recommending an additive. Also please note this is a 1990 which I understand had helical gears which supposedly are notorious for whine.
Thanks for you ideas based on experience.
Jim

[George Maz]

1990 trans had Straight-cut gears, yes stronger and noisier. The use of additives can attack the synchro metal...beware.
Sounds like an alignment issue of the trans. Bill Brodreau & Rockland Gear (ZF) have specific guidelines for install to minimize whine.

[Jim Stanley]

Thank you George, most helpful.

[George Maz]

Contact me via pm, with an email or text #. I'll forward the info I gathered when I had my transmission replaced.
Bill sent a pdf file, and the guy at Rockland gear spoke to me at length about his procedure.

[WARP TEN]

Originally Posted by Jim Stanley

I have recently had a clutch kit put in my car. It runs great with no problem. Both before and after the trans was pulled there was a gear whine. It is most noticeable when letting off the throttle in higher gears. Note: The trans oil was changed using 10w60 Castrol. The shop is recommending an additive. Also please note this is a 1990 which I understand had helical gears which supposedly are notorious for whine.
Thanks for you ideas based on experience.
Jim

Just as an aside, the whine you describe as being both before and after trans pull, and on deceleration, is also characteristic of rear end whine. Most of the stock rears on ZR-1s had some level of gear whine on decel, mine did with both the '93 and '95, and even my 4.10s installed by experts Haibeck Automotive on both had some. Of course it is hard to hear with a loud exhaust. -Bob

[gbrtng]

Originally Posted by WARP TEN

Just as an aside, the whine you describe as being both before and after trans pull, and on deceleration, is also characteristic of rear end whine. Most of the stock rears on ZR-1s had some level of gear whine on decel, mine did with both the '93 and '95, and even my 4.10s installed by experts Haibeck Automotive on both had some. Of course it is hard to hear with a loud exhaust. -Bob

Agreed ... and the tranny does NOT have straight-cut gears ... where did that idea come from?

TGF

[Paul Workman]

Originally Posted by gbrtng

Agreed ... and the tranny does NOT have straight-cut gears ... where did that idea come from?

TGF

U R correct, Glenn.

Doing some research on the ZF for a possible article in the HOTB, I came across some facts from reliable (ZF manufacture's docs and ZF mechanics), as well as the (many repeated?) myths, e.g., the "straight cut gear".

For anyone curious, this is what I've found so far...

Black vs. Blue tag'ed units essentially only denote where the units originated from. Black tag denotes those units which originally were built/supplied by Germany. Later, when GM attained the rights to build them in the US (Vernon Hills, IL), those units have the BLUE ID tag attached to the case, denoting their origin is the USA, including warranty work on all of the ZF transmissions used in the ZR-1.



In all there were 6 different iterations of the ZF used in the ZR-1 during the 1990 thru the 1995 production, but these are grouped into two major differences: The 610Nm units and the 540Nm units.

With exception of reverse gear, BOTH the 610 and the 540 ZF have helical cut gears.

Some background: "Straight" gear cut is where the cut is parallel with the axis of the gear. Straight cut gears have the advantage of zero lateral thrust as the force is at right angles to the teeth of the gear.
Helical cut gears' teeth are cut at an angle to the gear axis. The advantage is the gears run quieter, especially noticed as speed increases.
However there is a trade-off: helical cut gears also produce some amount of lateral thrust as the force is at an angle to the face of the teeth. When it comes to handling torque, often the limiting factor is the transmission's case's ability to stay together under the lateral forces developed by the helical gears.
The greater the angle, the less whine. The angle of the ZF gears was increased to mitigate some complaints about gear whine in the "610" ZF. However the trade-off was the torque rating: the increased angle reduced the gear whine, but also increased lateral thrust. Thus, the rating was reduced from 610Nm to 540Nm (approx. 450 pounds torque rating reduced to to 400 pounds, respectively).

Photos:

A cut-away of a ZF - just which version, was not available (610 vs. 540). Note the helical cut gears.

A good example of the differences in the gear cut angles and the advantages and disadvantages is the Muncie M21 and the famous M22 "Rock Crusher" (The rock crusher name was given to it because of the gear noise resulting from the shallower helix cut - that racers happily accepted in exchange for the strength.)

[ssrszz4]

Much misinformation cleaned up lol

Sent from my XT1585 using ZR-1 Net Registry mobile app

[George Maz]

Thank you Paul, and I'm looking forward to the the new article.

So, if I understand it a little more correctly now, the early version has "straighter" cut gears than the later version greater angle cut gears ...and both are categorized as helical cut design.
Seems like somewhere along the way people got used to just saying 'straight cut' when referring to the early version transmissions.

If increased trans whine wasn't present before clutch service, and also now has slightly noticeable whine while car is stationary, that would narrow it down to an alignment issue.

[Paul Workman]

Originally Posted by George Maz

Thank you Paul, and I'm looking forward to the the new article.

So, if I understand it a little more correctly now, the early version has "straighter" cut gears than the later version greater angle cut gears ...and both are categorized as helical cut design.
Seems like somewhere along the way people got used to just saying 'straight cut' when referring to the early version transmissions.

If increased trans whine wasn't present before clutch service, and also now has slightly noticeable whine while car is stationary, that would narrow it down to an alignment issue.

The best cure for trans rattle is the B&B exhaust.

After a couple hours in Ami's Z, I can't hear a damn thing!