Turbo-Geist

I had other things to do on Saturday so I picked back up yesterday after church. Both downpipes had to be removed to get the bell-housing off. It's been a while since I've done a clutch swap with the engine in the car and forgot what a pain it is without a lift.

Here's a picture for comparison to their Figure 7.

The fingers are supposed to be below the straight edge.



Here's a measurement they asked me to get for them last week. This is essentially from the mounting face of the crank to the pressure plate fingers. ~ 3.25"

Turbo-Geist

Today

I'm on the phone with McLeod right now. I sent them my other RXT 1000 and they received it Monday, April 17, 2017. I called and asked about it last week and they didn't have it in the system. Last week they said they would go look in the shop and send me an email regarding the status. This didn't happen.

I'm on the phone today and they are telling me they will go look in the shop. They go look in the shop and tell me it's on the stand for rebuild but needs a new floater plate and those aren't in stock. They expect to receive the new floaters tomorrow April 25th. The clutch can then be rebuilt and shipped.

Regarding the 3.25" measurement, according to McLeod, it should be 3.05". I'm not sure if this is when new or at the service limit. I guess when the new one shows up, I will check.

Turbo-Geist

I forgot to post this picture. The clutch is designed to operate with a throw-out bearing travel of 0.450" to 0.455". This picture shows the travel on the slave to be just under 0.500". So, the slave is extending far enough to do it's job, but the clutch disks aren't fully disengaging.

SBCGENII

Just saw a car with a bad pilot bearing that was locking up on the input shaft of the torque tube. The guy couldn't shift to reverse because it was spinning the torque tube.

Turbo-Geist

Thanks. I checked the pilot bearing and input shaft and they are both in good shape. This is similar. If the disks won't separate from the pressure plate, the driveshaft is still turning and won't allow you to place the trans in any gear when sitting still in neutral. It also made the car very difficult to shift during a race before it got to this point.

Chevy Guy

I'd say that is more than enough to disengage the clutch. The fingers don't have to move very much, and the clutch disk itself only has to move a fraction of an inch. That's more than enough throw to operate a clutch.

Turbo-Geist

Yes. This video was at the beginning trying to figure out the problem. I probably didn't word things correctly. There only needs to be 0.025" between each disk, so 0.050" total. It's not a 1:1 ratio between slave travel and pressure plate movement. They specify 0.0450" to 0.455" of slave travel and I believe I have verified it has enough movement. There appears to be a mechanical issue with the clutch/pressure plate assembly. With the pedal depressed and the slave as shown in the video, the pressure plate is still in contact with both disks.

Chevy Guy

Ugh - that sucks. Especially seeing how much of a bear a clutch can be on a C5. I have a mantic and I've been very happy so far. Some of these so called performance clutches are not made very well and need a ton of additional work, which in a C5 isn't so easy.

Turbo-Geist

The car is completely torn down waiting for a new clutch. I'm planning to go to the Pump Gas Invitational and race on May 13th so time is ticking. McLeod has the spare RXT clutch and is in the process of upgrading it to an RXT 1200.

I have been talking to them about the issues with the current RXT 1200 and they agreed to pay for shipping back to their facility. I'm not sure what will happen next, but it's a step in the right direction. I will take some pictures of the rest of the parts tonight and then ship the clutch assembly back tomorrow.

helga203

Your giving great info on Mcleod rxt clutches that is a hit or miss with these clutches. I'm in the same boat with this clutch. My going to go with the mantic and skip the BS with the rxt when i decide to tackle the work involved. My clutch still works it's just hard to get into gear. I've put over 20k on this clutch so it's not like i didn't get my moneys worth. Just not going to take a chance on them rebuilding it and having the same problem.

Turbo-Geist

Thanks. I'm not exactly sure what is going on but I'm trying to learn more than I knew before. I figured others might be in the same boat given some similar posts over the last year or two. There are some critical dimensions to check. The 0.200" of free play between the clutch fingers and TOB is a factory spec to give the fingers room to extend as everything wears. In my opinion, the other critical measurement is the recommended separation between the disks. If they don't disengage, it lowers the chances of ever making a quick fast shift with a synchronized manual transmission. I will be checking things on every install from here forward. If something doesn't check out, the clutch will not get installed and used. The 3.05" measurement that McLeod gave me is an easy one to check before you ever in install the clutch in the car. Although that's where the 0.200" of free play comes in. If you don't have at least that much you will be in the situation I am here with the slave bottomed out and the TOB right against the pressure plate fingers. As you will see in the next pics, something else was going on since the pressure plate wouldn't move far enough to fully release the disks.

Turbo-Geist

I decided to take each piece apart last night for a final look before shipping it back. Judging by some uneven wear, I'm think the pressure plate surface wasn't square and flat or the disks themselves were concave/convex.

Full assembly



Top Disk (in contact with pressure plate)
You can see that there is a lot of blueing but it was hottest out toward the edges of the disk.



Pressure Plate Surface



Floater Plate Top surface

Turbo-Geist

Top Disk - Up close view



Bottom Disk - Top side view
Similar bluing, but some pads appear "hotter" than others



Bottom Disk - Up close view

Turbo-Geist

Bottom Disk - Flywheel Side
Appears to be some bluing out at the tips



Bottom Disk - Flywheel Side - Up close



Flywheel Surface



Floater Plate - Bottom Side

Turbo-Geist

I took some measurements back when the clutch was new and took them again last night.

New top disk thickness: 0.310"

Worn top disk thickness: 0.280"

One pad is about 0.075" thick now


New bottom disk thickness: 0.325"

Worn bottom disk thickness: 0.295"

Floater plate is about 0.25" thick

Complete assembly weighs ~ 37lbs

inspector12

That thing looks like toast Ben LOL! Its definitely gotten hot!

BLOWNBLUEZ06@RKT Performance

Shimming is only to prevent over stroking of the slave to the point that it pukes the seal out and ensure enough space for the fingers to grow as the clutch wears. It doesn't affect or help with anything else except that you need. These hydraulic systems are self adjusting. They zero out at the point that it hits the pressure plate fingers. If you shim it, you only change the zero point but still get the .440" stroke regardless of where you start from. Changing to a Tick master (if you change to the 7/8" bore Tilton cylinder) increases the stroke capability to roughly .513".

Turbo-Geist

A 1/16th of an inch difference at the slave can mean the difference between having good release, i.e., 0.0125" between each side of each disk or dragging, i.e., with 0.00625" between each side of each disk. Not enough clearance will cause poor shifting and ultimately lead to worn parts in the clutch assembly and the transmission.

BLOWNBLUEZ06@RKT Performance

Not sure if this is a reply to my comment. If so, I absolutely agree, however shimming doesn't affect how much stroke is yielded. The zero point is reset when you shim it and the pressure plate continues to get stroked the same amount regardless.

Turbo-Geist

Thanks, Bret. I totally understand what you are saying now. The only reason to shim is to get the slave within the recommended range as far as the A and B measurements. As I understand it now, this will not improve overall travel or give you more stroke. The slave is still going to travel 0.440". By adding the shim, it moves the slave forward but it ends up getting pushed back down and takes up some of the free space below. The shim only adjusts free travel but can't make up for a clutch that wasn't built correctly from the beginning. Make sense?