Low whining sound from undercarriage

[ZR11974]

Originally Posted by Dynomite

The Pilot and Engine both rotate at same speed whenever Flywheel is Engaged with Transmission. It is only when depressing Clutch Pedal and shifting that the Pilot Bearing is spinning within the Flywheel/Crankshaft.

Some links related to the Pilot Bushing and repair.

TRANSMISSION
Post 35 - Pilot Bearing
Post 36 - ZR-1 Transmission Install and Lift Tricks
Post 37 - Vibration Issues Diagnosis
Post 38 - Throwout Bearings and Clutch Forks
Post 39 - C4 Beam Plates and Installation

Dynomite,
Thanks so much for helping me start my research. I love learning more about these cars!
I appreciate your efforts, my friend.

Geoff
'90 #2591

[oldpro]

Pilot. Bushing mine did the same thing

[Ccmano]

Take it to Crossed Flags Performance in Magnolia if your close enough. There are not many good ZR-1 shops around, he’s the closest to you.

https://www.crossedflagsllc.com/

Steve Schroeder knows what he’s doing on these cars. I agree with the pilot bushing theory based on what I’ve read.
H

[ZR11974]

Old pro and ccmano, thank you for taking the time to respond. It's so great to have a forum like this available to a newbie, like me.
And, magnolia is only a few hours away. Next door, by texas standards.
I will definitely look them up!
Thanks again and take care out there!

[ZR11974]

Kenny,
Thanks for the input. I've already had the car to see Corey, but of course it wasn't making this sound when he did the initial once over for me. Corey is great, and I'll be reaching out to him first to get his thoughts. Really helpful, genuine guy.
I would love to come out to the bbq! Where it's the best place to get info about it?
Thanks again and take care.

Geoff
'90 #2591

[Dynomite]

Originally Posted by Hib Halverson

(edited)

Gears in the early ZF S6-40s have a slightly smaller helix angle and that's why the early transmissions are a little more noisy and have a little higher input torque rating.

Regarding the ZF S6-40 ZR-1 Transmission.......I find that that the smaller helix angle (of the gear teath) attributing to a little more noise and higher input torque rating is of technical interest and worth documenting........something not described before

[Hib Halverson]

Originally Posted by Dynomite

(snip)something not described before

The change was made mid-year 1993, as I recall. Without trying to find some of my old S6-40 articles I can't say for sure. Graham remembers more about that change than I, so maybe he can confirm the time line.

The early S6-40s were designed when GM was still considering a turbocharged LT5 for the future and it wanted some extra torque capacity. After it became obvious there never would be an LT5TT, GM decided to address customer complaints about noise and decided to increase the helix angle as well as the other changes Graham details. The decision resulted in the later transmissions which were quieter and made less noise.

[grahambehan]

The change made to helix angle as mentioned by Hib was a significant change to radiated gear mesh frequency because it increased contact ratio, ie the number of teeth in mesh. There are detail changes to tooth profile and flexibility that affect the load progression across the teeth and thereby reduce the noise generated as the gears mesh also.

Graham

[WARP TEN]

Originally Posted by grahambehan

The change made to helix angle as mentioned by Hib was a significant change to radiated gear mesh frequency because it increased contact ratio, ie the number of teeth in mesh. There are detail changes to tooth profile and flexibility that affect the load progression across the teeth and thereby reduce the noise generated as the gears mesh also.

Graham

As usual, the voice of knowledge and reason. Thanks Graham --Bob