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6 Speed Transmission...

IraPlayer

Active member
Joined
Oct 3, 2001
Messages
29
Location
Dublin, CA, USA
Corvette
1994 Black/Black Coupe
Hi all, first post...

I recently bought a 1994 Black/Black Coupe with a 6 speed transmission.

I have noticed that when I'm not playing (engine noise minimal w/Corsa exhaust) I notice a significant increase in the gear noise in third gear coompared to all others.

1st and 2nd I'm sure are quieter. 4th and above tire noise starts to impact evaluation.

Is this a problem I need to address, or just normal for the tranny?

Thanks in advance for the help.

Ira :confused
 

Yoda

Well-known member
Administrator
Joined
Oct 12, 2000
Messages
4,885
Location
Amarillo, TX
Corvette
1981 UL5
Ira ~ Welcome to The Corvette Action Center Community ~

Ira,
Sorry I can't help you with your question, but, there are plenty C4 owners here that can, and will be along shortly.

I just wanted to jump in and welcome you nieghbor.. I'm just over the hill in Modesto :D You should like this place, we have the best members and helpful, friendly and sometimes a little funny too ;)

Hang in there help is on the way. Welcome aboard enjoy the ride.
 

twiget

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Nov 2, 2000
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1,302
Location
The Land of Enchantment
Corvette
In the market
Ira, I have to agree with Racer. Check the oil in your tranny. Though GM dosent recommend changing the oil, just checking it and topping it off if it's low, the oil really does need to be changed.

According to the guys at ZR51 Performance, depending on the oil in the tranny it should be changed between 10,000 and 20,000 miles. From the factory, GM fills the tranny with Havoline which is good for 10K. You can also use Mobil 1 5W-30 (the same stuff you use as engine oil) also good for 10K. Red Line MTL (Manual Tranny Lube) is good for 20K. And then the stuff recomended by ZF (the tranny's manufacturer) and the guys at ZR51, Castrol 10-W60. This is the motor oil for the BMW M5, and BMW is the exclusive importer of it. You will have to contact your local BMW dealer to get it. It's good for 10K, but provides superior lube and protection.

I just changed the tranny oil on my GS a week ago to the Castrol and as soon as I put her into reverse and backed her off the driveway I noticed a huge diffrence. Like you, I had noticed increased tranny noise in lower gears, a whining, almost like a turbo spinning up. And the shifts where getting progressivley more notchy and harder. With the changing of the oil the tranny noise was noticebly less, and the shifts where much smoother and easier to find.

If you have any questions about how to change the oil in your tranny contact Bill Boudreau of ZR51 at BillB@zfdoc.com.

Hope this helps.

Jason
 

IraPlayer

Active member
Joined
Oct 3, 2001
Messages
29
Location
Dublin, CA, USA
Corvette
1994 Black/Black Coupe
twiget said:
I had noticed increased tranny noise in lower gears, a whining, almost like a turbo spinning up. And the shifts where getting progressivley more notchy and harder

I'm not noticing the notchy and harder, but I have nothing for comparison. :D

I plan on doing the tranny oil change this weekend. I thought I'd ask first to make sure I'm not causing damage. The "turbo" sound is quite descriptive. It is really restriced to 3rd gear. I ran the "test" again, (running slower than I like in 4th and 5th to keep tire noise down). The noise definitely peaks in 3rd.

I'll let you all know post change.

I'm also going to join a local Corvette club. Hopefully a few will have C4's with the 6 speed and can have a listen.

(I don't have a "regular" mechanic for the Vette at this time. My experience with having someone I don't know give an opinion is almost always "This needs a compete rebuild. You're lucky it got you this far.":bash )

Thanks for the input.

Much appreciated.
 
B

Barbie

Guest
twiget said:
From the factory, GM fills the tranny with Havoline which is good for 10K.



Hey Jason, I've heard rumours that factory fill had additives in it. Do you have any knowledge of this?

Welcome to the CACC Ira! Most ZF 6 speeds have audible gear noise which is considered acceptable. I get a slight amount out of first gear, and change my oil annually. Very reliable transmissions though.

Barbie
 

IraPlayer

Active member
Joined
Oct 3, 2001
Messages
29
Location
Dublin, CA, USA
Corvette
1994 Black/Black Coupe
Barbie said:

Welcome to the CACC Ira! Most ZF 6 speeds have audible gear noise which is considered acceptable. I get a slight amount out of first gear, and change my oil annually. Very reliable transmissions though.

Barbie

I feel very welcome already. Thanks all for the input.

Ira
 
D

Dennis

Guest
There has been much discussion on this subject on several of the forums. I have had correspondence with Bill Boudreau at ZFdoc and as a rebuilder of ZF's, he has to be considered expert.
The factory fill GM P/N 1052931 is not just a 5-30 motor oil. It has additives to meet a GL-3 Gear lube requirments.
Bill does not recommend using Mobil-1 in these transmissions. He has seen wear on the synchronizers in ZF's that were using it.
His favorite is the Castrol RS 10W-60, BMW P/N 07 51 0 009 420, and recommends changing it every 10,000 miles.
He also recommends changing the GM lube at 10,000, and the Red Line MTL at 20,000.
The difference between these three products is probably slight. Changing them at regular intervals is important, even if GM does not require it.

BTW, I have the BMW RS in my Grand Sport.

:beer
GS-598
Dennis
 

twiget

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The Land of Enchantment
Corvette
In the market
Everything I know about the ZF I learned from Bill Boudreau.:) He really is the expert on the ZF tranny's. Glad I could help though.

Barbie,

I guess Dennis answered your question about the factory fill. It's the first I had heard about any additives being added.

Jason
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I put after market Castrol in our 89 six speed and it was a major mistake. Not only was it noisy, but when the outside temperature started cooling off, it was hard to shift.

Went to my C4 expert at the local chevy dealer. He said to run nothing but the factory recommended GM fluid. You can buy it from the G.M. dealer. It appears to be nothing more than 5W-30 oil. However, it smells like GL 3 or 4. Anyway, put that it and it was fine from there.

Serviced the 90 six speed with the same factory stuff.


These are noisy transmissions by nature. The two piece flywheel makes plenty of raquet during shut down and slow idle along with the meshing of the gears.

Our is strong at 150K. You should get plenty of long life from yours.
 

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