89 Daytona - clutch wont fully disengage?

[jory]

So I just got my daytona back running after swapping the tbi for a 2.2 turbo. I used a TIII pressure plate (orig came with a large spline disc, used it in my old car) with a small spline disc and 6 bolt flywheel. I changed the clutch cable because I noticed the old one was frayed, the cable came out of a 88 shelby z with a555.
Now when I started the engine I went to pull it up on ramps. I pressed the clutch and tried putting it in first, and I was met with much resistance. I jammed it in with no grinding but it couldn't have been good for it. When I start it in first with the clutch depressed it acts like it wants to creep forward. The pedal feel is great and the friction point is right where it is supposed to be. with the engine stopped it goes through all gears fine. So what gives? I don't want to pull the transmission again.

[ShelbyZD]

I pressed the clutch and tried putting it in first, and I was met with much resistance. I jammed it in with no grinding but it couldn't have been good for it.

I think that's pretty standard. If Im doing 10kph+ in my 88 Shelby Z it doesn't like to be put back into 1st. I'd expect it's some kinda safety so your engine doesn't over-rev if you accidently put it in 1st when your past 5k rpm in 2nd.

[puppet]

This might have more to do with the lateral position of the crank shaft inside the block. Don't be surprised if the next time you change the oil you see flakes. That will be the #3 thrust bearing on the main.

[Force Fed Mopar]

I think that's pretty standard. If Im doing 10kph+ in my 88 Shelby Z it doesn't like to be put back into 1st. I'd expect it's some kinda safety so your engine doesn't over-rev if you accidently put it in 1st when your past 5k rpm in 2nd.

Put down the pipe

So I just got my daytona back running after swapping the tbi for a 2.2 turbo. I used a TIII pressure plate (orig came with a large spline disc, used it in my old car) with a small spline disc and 6 bolt flywheel. I changed the clutch cable because I noticed the old one was frayed, the cable came out of a 88 shelby z with a555.
Now when I started the engine I went to pull it up on ramps. I pressed the clutch and tried putting it in first, and I was met with much resistance. I jammed it in with no grinding but it couldn't have been good for it. When I start it in first with the clutch depressed it acts like it wants to creep forward. The pedal feel is great and the friction point is right where it is supposed to be. with the engine stopped it goes through all gears fine. So what gives? I don't want to pull the transmission again.

You did put the disc in the right way, right? Beyond that, if you used a jack to raise the clutch fork lever all the way up as far as it will go (I think I saw you post in DodgeZ's thread that you did) and it isn't bottomed out to the trans case, it's either a PP or flywheel problem.

[jory]

I dont think the disc would even fit backwards, lol I got at least a week before the title comes in so I've got some time to play around with it. I don't want to take it on the street loud like it is, not to mention my nosy neighbors. I might just drop the transmission and swap the plate if I can't make it release by driving it. The last thing I want to do is mess up my synchros.

[shelbymopar89]

Did you use ARP crank to flywheel bolts?

[Vigo]

I think that's pretty standard. If Im doing 10kph+ in my 88 Shelby Z it doesn't like to be put back into 1st. I'd expect it's some kinda safety so your engine doesn't over-rev if you accidently put it in 1st when your past 5k rpm in 2nd.

Hes talking about putting it in first from a stop.

What you're talking about is normal. There is no safety mechanism, but once you understand what is happening it makes sense.


In your manual tranny you have two shafts with gears on them. On one shaft the gears are splined onto the shaft and are always spinning the same speed as the shaft. This shaft is (basically) connected to your tires and its speed is determined by your road speed (output). On the other shaft, the gears ride on bearings and may be moving at very different speeds from the shaft they ride on. This shaft is basically connected to your engine and its speed is determined by engine speed (the clutch disconnects this shaft from the engine). That's the input shaft. The gears on these two shafts are always meshed with each other.

SO, if your car is at a stop but your engine is turning 800 rpm, and you are in neutral, the input shaft will be moving at 800 rpm while the gears that ride on the shaft will not be turning at all (0 rpm).

If you are rolling down the road at 30 mph in neutral and turn the engine off, all of the gears will be spinning on their bearings while the shaft they are on is at 0 rpm.

When you try to engage a gear, what you are doing is connecting the gears on the input shaft to the shaft itself, and to connect them they have to be turning the same speed so that the splines/teeth on the shift collar can slide on and engage.

Your synchronizers in the tranny are basically tiny clutches between your gear and the shaft that bring them to the same speed by spinning up or slowing down the input shaft to the same speed as the gear. Since the gear is constantly meshed to the other gear, which is effectively solidly connected to your tires, its speed will be related to your road speed, and so it has all the momentum of the whole car resisting a change in speed, while the input shaft only has the inertia of the shaft itself to overcome to change speed (assuming you have the clutch pushed in and the engine thus disconnected).

So you can imagine that at a given road speed, say 20 mph, the input shaft and the engine would be turning different speeds in different gears.

i.e.

1st 4500 rpm
2nd 2700
3rd 1800

etc.

So if you're going 20 mph in 3rd and you want to shift into 1st, the first gear synchronizer has to overcome the inertia of the input shaft and equalize the difference between the numbers shown above by speeding up the shaft by (4500-1800=) 2700 rpm. This is a difficult job for the synchro, and its powered entirely by your arm pushing on the shifter.

When you upshift, the synchro would actually be slowing the shaft down instead of speeding it up. Upshifting is easier because you generally only upshift sequentially, like 1-2, 2-3, 3-4, etc, so the difference in speeds is limited. Also, when you push in the clutch, the shaft slows down naturally due to bearing friction, and so most of the work the synchro would do is already done before you even start using it.

The exception to that, is if you shift very slowly, or put the car in neutral for a while and then engage ANY gear, the shaft will actually slow down PAST where you wanted, and be sitting there running at idle speed (~800 rpm). So if you want to shift from 2nd to 3rd at 20 mph, you want that shaft to be running 1800 rpm for the gear to engage, but if you do it too slowly the shaft will actually drop from 2700 rpm all the way back down to idle, and the synchro actually has to speed the shaft up, even though you are upshifting.

THUS, if you are coasting down to a slow speed like 10 mph and then trying to get into first, your synchro will be hard pressed to speed the input shaft up from either 0 rpm (if you've been coasting with the clutch pressed in) or 800 rpm (if you've been coasting in neutral with the clutch out and the engine idling) to the target speed of ~2500 rpm.

It WILL do it if you push hard enough and long enough, but it wears the synchro quickly if you do this regularly. Not only that, but if you 'get used to' just powering through resistance in the shifter, you'll be much more likely to misshift into a lower gear and not notice it, which could damage your engine when you let the clutch out if the road speed is too high for the gear you've pushed it into (over-revving).

So that's why the shifter resists being put into 1st when you are rolling faster than about 5 mph.

The easy way to get around this that's nice to your synchros and will make them last longer is to learn to double clutch, but thats another long explanation and i've got to make a movie showing in 30 minutes!

So is this the wrong thread to be writing sticky material in?

[jory]

^great post, stuff everyone should know.

I swapped pressure plates and it fixed my problem. How much power/boost should a stock T1 clutch hold? Now that the transmission is perfect, I think I need to do the head gasket.