Adjusting clutch fingers too often.

[Paul Baker]

Three or so years ago I lost high gear. After some research I figured out that I just needed to adjust my clutch fingers. I did so, and all was good. For a couple months. Then they fell out of range again. I assumed my clutch spring was weak, so I installed the spring spacer sold by the vendors. That worked great for a year or two, but then this past summer I started to lose high gear again. I checked and, alas, my clutch fingers were out of spec again. I tightened them once more and my clutch is back to working great. But for how long?

One thing I've realized is that I start to loose high gear when I put lots of weight in the car which is usually when I give rides with multiple people in the car.

My friend was thinking it may relate to the clutch disks. I have Jack Rabbit disks that Kevin Prus put in when he rebuilt the engine in 2009.

I do not drive the car a lot, so the frequency of this problem is concerning. We're planning to take it apart later this Spring and see if we can find the culprit but until then I was hoping to find somebody that may have experienced this previously to help focus our effort.

Thanks in advance!

[Jerry VanOoteghem]

Go back to the stock Ford discs and never look back. Once the Jack Rabbit, (turbo 400), clutch discs are allowed to slip a bit they are done for. Yes, you can adjust and get them back, but it won't last. Jack Rabbit clutches require a higher strength spring to help prevent this.

Also, I'm wondering what your driving habits are. Do you slip, or feather the clutch when shifting to high? Shifting to high should be a quick engagement once the engine has been allowed to slow a bit, to match the vehicle speed.

[speedytinc]

You can not allow the clutch to slip with 400 disks. Slippage wears out the lining material. You will need to replace the clutch disks. Spring pressure must be strong. I NEVER use original springs, even if testing shows 90#. Get the stronger replacement spring that test @ 110-120#. As extra insurance, I give another 1/2 turn on the 3 fingers above the 13/16 dimension. Engagement should be like a modern manual transmission clutch.

I have seen maladjusted clutch linkage cause a less than consistent full release of the pressure on the spring. It can be caused by the clutch lever adjusting bolt slightly touching the hand brake lever cam. In any case, its operator or mechanical adjustment error.

I run these lined disks in all my T's. All are way over 20 HP. One is a Rajo powered touring that will burn rubber. Never had a slipping or wear issue.
One T with around 10k miles got an engine/transmission refresh. The disks showed no wear, so I reused them. That disk pack has over 15k miles on it now.

[Paul Baker]

Thanks guys. Your info is very helpful. But please explain how the disks would change the 13/16ths clutch finger setting?

FYI - I've learned to just let the clutch quickly get into gear and not feather it. I used to do that, but haven't in a long time. Also, I only drive less than 1000 miles/year (if that), so don't see how such a dramatic change can happen so quickly.

[speedytinc]

Thanks guys. Your info is very helpful. But please explain how the disks would change the 13/16ths clutch finger setting?

FYI - I've learned to just let the clutch quickly get into gear and not feather it. I used to do that, but haven't in a long time. Also, I only drive less than 1000 miles/year (if that), so don't see how such a dramatic change can happen so quickly.

The lining wears down from slippage. Thus, the pack narrows also decreasing spring pressure.
Any slippage wears the disks quickly.

[RVA23T]

You dont have standard metal clutch disc, so the 13/16" might not be enough for the jackrabbit /turbo 400 disc after their initial use.

[speedytinc]

You dont have standard metal clutch disc, so the 13/16" might not be enough for the jackrabbit /turbo 400 disc after their initial use.

Even with OEM style steel disks, the 13/16" dimension is a starting point.
See the service manual.
After a test drive, the fingers are to be adjusted to remove excessive slip or lighten up the engagement for some limited slip.
Dont be a slave to the dimension.
With th400 disks, the manual dosent apply in this respect. There must be a solid & sustained lock up.

[Allan]

Some transmission discs fail when there is water in the oil. It affects the bonding agent that glues the friction material to the metal plate. This was a problem with early automatics which ran the trans fluid through the radiator bottom tank for cooling. Any little flaw let water in the trans fluid.
Your car having sat for a length of time may have accumulated enough condensation to cause a problem.

Allan from down under.

[Jerry VanOoteghem]

But please explain how the disks would change the 13/16ths clutch finger setting?

As the discs wear in thickness, the 13/16ths dimension will decrease. Subsequent adjustments will reestablish the 13/16ths dimension, until finally you run out of adjustment.

[Paul Baker]

Thanks everybody. Definitely know where to look seriously now.

[Rich P. Bingham]

Be aware of lining fragments in your oil as the clutch discs fail. They can cause an engine failure. From experience, I agree the original clutch pack is best. Lining fragments likely caused a piston-pin to seize in my T by blocking the oil hole.

[Rich P. Bingham]

Be aware of lining fragments in your oil as the clutch discs fail. They can cause an engine failure. From experience, I agree the original clutch pack is best. Lining fragments likely caused a piston-pin to seize in my T by blocking the oil hole.

[Norman Kling]

I even pull the parking lever into neutral position while waiting for a signal. It is much safer than holding the pedal in neutral. With the foot it is easy to either slip the band on the drum or wear the disks. Ok at a stop sign when the stop is very short time, but with the modern signals it can be quite a wait.
Norm