95 6-Speed weirdness (and a million other questions)

[ediconu]

6-Speed owners,

Part I:

Have any of you guys had your transmission not want to go into 1st gear when the car is stopped? I can get it in, but sometimes I have to go to 2nd and then push it up thru the center into 1st.

For example, I'll approach a red light, take it out of 4th or 5th gear, not downshift through the gears, then when I try to put it back in first after I've stopped, it feels like I'm pushing the shifter into a wall. I can go into any other gear with no problem (reverse excepted, but that's another issue) I can usually put it in 2nd, then push it thru the middle and it'll go into first smoothly. The other option is letting off the clutch with it in neutral, then hitting the clutch and putting it back in gear.

Would repalceing transmission fluid make this smoother?


Part II:

Often when I'm driving at low speeds with the windows down and I shift out of first into 2nd, it feels smooth, but I hear a small clunk coming from under the car. I don't really feel it, but it's loud enough to upset me. I don't think I'm doing anything the transmission doesn't like, but I may be. (I can only hear it when I'm next to a wall or line of cars, something to reflect the sound back to me.)

On an unrelated note, should I be able to hear something spin up when I'm going 40 mph and it's time to downshift? I put it in 2nd gear and I hear a little "Zip" noise like something synchronizing to the speed, but the clutch is all the way in. I always thought it was fully disengaged when the clutch was all the way in.

Does anyone have a good resource about the specific transimission in a 1995 vette that includes information about the best way to drive it, all the little noises, and any basic info about how to tell it's time for fluid change / maintenance / repairs before it compeletely stops working?

I'd also like to know how the overdrive is different from the rest of the gears and why there's such a loss of power related to it's use.

I'm severely bent on learning as much as I can about all of the operations and mechanical aspects of my corvette (and everything else on the planet...). Any assistance in getting there is greatly appreciated. FWIW: I read the how-stuff-works about transmissions already and found it incredibly interesting, but not specific enough. http://auto.howstuffworks.com/transmission.htm

Thanks!
Mike

 

[Tuna]

To part 1 - Yes.

This happens fairly often as I roll up to stops with the car in neutral a lot. Then when I get ready for first, it does not want to go there until selecting another gear.

This appears to be related to the alignment of the synchronizers and the gear - they are butting edges and refuse to asjust positions to engage. By selecting another gear that is better aligned, the first gear alignment also shifts and I can select first.

Other times when this happens and I'm ready to go, I just ease out the clutch with pressure on the shifter and it slips into first and away we go.

Now to see what others say!


Part 2 - this may be a bad u-joint in the half shafts or drive shaft. I'd look there first.

That's all I've got.

 

[Skant]

Part 1: This is so normal that it's actually in the owners manual (at least for my 96).

The method documented is to double declutch. That is... press in the clutch, shift to neutral, let out clutch, push in clutch again, shift to first.

It's not uncommon on racing transmissions.

I actually do this every time I shift into 1st now. A friend recommended that this will help the synchros last longer in general.


Part 2: The ZF transmission is downright noisy. It makes all sorts of whirrs, clanks, gravel sounds, vibration sounds, etc. Some of them even sound like bad noises like it's going to break or something. It makes all these noises because it's a very very tough transmission. Making a transmission quiet requires techniques that generally make it more fragile. So I think of the noises as a reminder of how tough this tranny is. It's designed to be tough, not elegant. Exactly what I want!

That being said though, I'm not sure about the clunk going into 2nd. This tranny makes really annoyed noises at you if you don't match rpms well when shifting. So that might be it. Or it might be a real problem.. more likely with the rear end than the tranny.

As for the 'spinning up' sounds... yeah that's normal. Did I mention this transmission makes a lot of whirrs among other noises?

From what I understand... if something goes wrong with this tranny, you'll _feel_ it. Don't try to diagnose it with your ears, you'll just scare yourself.

Sounds are a good indicator about the rear end, though...

- Skant

 

[caddy]

What type of oil?

I have a 94' LT1 Coupe with a 6-speed and I was wondering about changing my transmission oil, what is a good brand or type to use?
:confused :confused

 

[Tuna]

Re: What type of oil?

I have a 94' LT1 Coupe with a 6-speed and I was wondering about changing my transmission oil, what is a good brand or type to use?
:confused :confused

I use Red Line MTF in my 92 6-speed. Works really well.

The 03 doesn't have enough miles on it to worry about changing the oil in the trans yet.

 

[caddy]

Great thanks, BTW would the Owners manual tell me how many quarts I need, I don't want to sound to stupid, but what all is involved in draining/replenishing the MTF?
thanks

 

[ediconu]

I'm glad to hear that the noisiness is perfectly normal and good. I was reading about the contact area / helix design and what not that make it quieter than other transmissions that have similar power... I think the clunk is when i don't give it quite enough time to sync the speeds up when i'm shifting. I'll assume everything is as it should be until i feel a problem or some noise that i grow accustom'd to becomes worse.

I'm still interested to know if any resources where people tear down a C4 transmission and talk about the peices and functions. More information is more better.

Mike