zf 6speed - 1st gear whine - normal or ?

[froggy47]

96 LT4 49k miles.

This car is new to me so I can't compare to when it had fewer miles. The tranny has some gear whine in 1st only. Is this normal?

Also hard shifting into reverse. I read this is a symtom of clutch master & slave cyl needing work.

Any ideas?

Thanks!

 

[B17Crew]

ZF Six-Speed

froggy,

I have 44,700 miles on my LT4, and I too have a subtle gear wine in 1st gear. I’m pretty sure that it’s a characteristic of the ZF tranny. I’ve had four C4’s, three of them had the ZF, and all three of them had a subtle whine. I’ve heard that using Redline Synthetic tranny oil will help reduce the gear noise -- More knowledgeable forum members can chime in on specifics. A simple tranny oil change may be all that you need.

As for getting into reverse, I’ve noticed that my ‘96 will occasionally take a little more effort to reach reverse. The ‘93 and ‘94 six-speeds I had came with the reverse lock-out (reverse lock-out was done away with in the ‘95 model year), the ‘93 and ‘94 didn’t put up much of a fuss trying to get into reverse, but I have noticed that my ‘96 will occasionally take a little more effort. It’s intermittent, and does not happen often, so I don’t think it’s a part failing, just another characteristic of the ZF.

Over the years, I’ve talked to other ‘96 owners about the high effort going into reverse, none of them have had any ill effects.

Hopefully, other C4/ZF 6 owners will offer up their personal experiences with their cars.

B17Crew


P.S. That gear whine -- I kinda like it, it’s a mechanical symphony to my ears!

 

[Vettelt193]

I get gear whine all the time with my '96. I really think the so called 'update' to these transmissions is the worst thing they could have done. I wish I had my old '93's 6-speed... It worked much better... never gave me any problems.

 

[Rob]

Bob,

Regarding the 1990 ZF transmission chatter, the following was posted over the ZR-1 Net on July 12, 2000:

From ZF:
"All S6-40 transmissions installed in the C4 Corvette contain 100% helical gears. In fact, all of the gearboxes ZF produces for passenger car applications, contain helical gears, the primary purpose of which is to increase gear contact ratio and thereby minimize gear noise.
There is one major difference between the model year (1989-1992) and (1993-1996) C4 Corvettes - the contact ratio for the later years was further increased in order to reduce the gear noise. There, however, was a very slight reduction in torque capacity of the gearbox (from 610 Nm to 540 Nm) when ZF increased the gear contact ratio in the later year transmissions.
The noise you hear in 1st gear is commonly termed "1st gear growl". This noise is inherent to the design of the 610 Nm gearbox and in no way is detrimental to the reliable function of the transmission and your [Corvette]. With the increased gear contact ratio in the 540 Nm gearbox, ZF also was able to reduce the "1st gear grow"."

Basically, it's normal. They all do that, including my '90 when it's parked, in neutral and idling.

 

[sothpaw]

what about 6th?

I get a whine--I would call it a burble--in 6th if I have my foot
on the gas lightly, as in cruising. If in 6th and giving it gas to
actually accelerate, there is no burble.

Is this a bad bearing? It's been like this for a while.

 

[B17Crew]

sothpaw,

Are you experiencing the “burble” below 65 mph while in 6th gear?

Reason I ask is I remembered reading in Gordon Killebrews’ booklet, “Top 50 Questions from Corvette Owners and Dealers with Answers,” that 6th gear should never be used below 65 mph. Here’s the paragraph that I am referring to. (page 18, paragraph G)

Six Speed Shift points
Never use 6th gear below 65 mph. If, on going up an incline, the engine rpm drops too low causing a chatter in the drive train, merely downshift to 5th gear. To give you and idea of the 6th gear ratio, a Doug Nash four speed overdrive was .68 ratio. The ZF 6th gear is .5 ratio.”

Next time while on the highway check your speedo and see if you are below 65 mph when the sound occurs. If it’s not related to the paragraph above, then you can move on to other possibilities that may be causing the burble.

B17Crew

 

[trrgod]

The gear whine is NORMAL. These were originally a truck trans and were built to take a beating but in my opinion they are too noisy and very hard shifting.
I still love it and have fun driving it even after all these years======Mine is an 89.

 

[Skant]

The ZF6 is just plain noisy. It makes all sorts of whirrs, whines, and grumbles.

You're driving a street legal race car with a very strong transmission. It's the price you pay for that strength. It's nothing like a cozy quiet Cadillac.

So just consider it part of the vette experience. This is the way all street legal race cars are. You sacrifice quiet for performance.

- Skant