GT500 Twin Disk Clutch Install
This page is to document my project to install a flywheel and twin disk clutch from a Shelby GT500 in my 96 Cobra.
My clutch recently started slipping. It's a McLeod aluminum flywheel with a McLeod pressure plate and a dual Kevlar clutch disk installed for me several years and about 40K miles ago. It has never been right, howling loudly when engaging in first gear for the first few years. And I am sure my beating on it did not help. regardless, we need a new clutch. Since I am building a high power Teksid Terminator, I figured I might as well upgrade to something that can handle the power. So I ordered a Shelby GT500 twin disk clutch, flywheel, pilot bearing and throwout bearing. it also will necessitate the upgrade of my T56 to a 26 spline input shaft, so I also ordered a Liberty 26 spline shaft along with a shim kit and an adjustable pivot ball for the linkage. The latter arrived today:
The clutch kit arrived today, along with a throw-out bearing and a kit of parts to fix my backup light switch and connector.
Here is the flywheel:
And the pressure plate with the twin disks:
Bolts and throw-out bearing: (TOB not part of the kit)
The backup light switch repair parts: (also not part of the kit)
I unhooked the battery, and removed the upper and lower shift boots:
I removed the shifter and unhooked the reverse lockout solenoid connector:
I got the car up on jackstands and crawled under it to get started. I unhooked the O2 sensors:
Crawling around, I noticed that the clutch linkage cover bolt hole was stripped and the clutch linkage cover was gone. There is a huge hole through which anything can get into the bell housing. I suspect this may be part of why the clutch failed after about 40K miles:
I then went to the driveshaft to pull it out:
I broke my Craftsman universal knuckle on this and broke the middle finger of my right hand in the process. Sears replaced the universal knuckle. I gave up and decided to take my car to a shop that is equipped to do the job. After asking around, I selected a local performance shop who's name I have redacted because I can no longer recommend them. Read below to learn why.
Took my car up to the shop to have them do my clutch replacement. I was going to wait for the car, but as we got into it, it became clear that there were other problems that will also need to be addressed, so the car would have to be left.
When they got the transmission out, it was clear that the passenger side motor mount is broken:
Polyurethane motor mounts were ordered.
We then got a look at the flange on the passenger side exhaust manifold flange and saw that I did have the leak I suspected from my datalogs. Bank 2 trims were running about 5% lower than Bank 1. Here is the evidence:
New exhaust seals were ordered.
They pulled the front cover off the transmission to do the input shaft upgrade and found metal shavings in the oil. So off to the local transmission shop it went along with the input shaft, and a steel TOB sleeve. The shift forks will now get upgraded, so the only thing that will be missing from a Viper spec T56 upgrade will be the output shaft.
Here's a shot of the rear of the engine:
I also snapped a picture of the front pulley, which is the pulley from the KB blower kit:
The black Prothane motor mounts were installed while we waited for the transmission work to be done.
After the transmission was gone through and nothing bad was found, they tried to put the 26 spline input shaft in, and they learned that my transmission was not a Cobra spec transmission. It is a D&D BA3, which has a 2.97 first gear as opposed to a 2.66 first gear. It also has steel shift forks. But the big impact was that the Liberty Cobra spec input shaft would not work for me, so a new D&D BG45 input shaft had to be ordered and overnighted. After that, the transmission went together smoothly.
The guys installed the twin disk clutch and tried the stock clutch linkage ball and it turned out that the stock ball fit perfectly. The clutch lever did not need any modification and there was no interference with the clutch lever weight. (Note: this was not true. See below.)
We also replaced the backup light switch which had had 60 ohms of resistance from the day it was new. Now my backup lights work again. The guys tapped the clutch lever cover for a new bolt and installed the new clutch lever cover for me so I now don't have to worry about crap getting into my new clutch.
The clutch seems easier to operate than a regular GT clutch now. It seems a bit grabby, but I suspect it will smooth out as it breaks in. I am not noticing any of the noises that others have complained of. I think I am really going to like this clutch.
I am noticing some fairly significant vibration from the polyurethane motor mounts, especially as I let up on the gas and wait for the idle to drop from about 1200 to 850 RPM. Once at 850 and over 1200, I don't notice any vibration.
Now I can get back to tuning.
After driving with this clutch for a year, I still love it. The slight grabbiness went away after a short break-in, and the clutch has been very strong, but civilized since. It can easily handle anything my 341hp KB Cobra can throw at it.
After driving with this clutch for a little over 18 months and 9,000 miles, it has started to occasionally chatter and slip. I am not real happy. I have searched the internet and have learned that the GT500s are having lots of clutch problems, and Ford is replacing them with a different clutch and flywheel. I am running something less than 342 HP, 357 ft-lbs of torque. Grrr.
Per my local Ford guy, the replacement part number for the new GT500 clutch kit is: 7R3Z-7LS96-A.
Today was the day the new clutch was installed and this is what I learned.
When we got the clutch fork cover open, we saw that the clutch fork was slammed against the transmission, so it was keeping the clutch from fully engaging at any time. It was so bad that a bolt on the transmission had pressed into the lead fork weight to the point where you can see the lettering from the bolt head. It is clear that the clutch was never fully engaged, so it was probably always slipping a bit. It was clear from the clutch fork geometry that the stock pivot ball needed to be replaced with a properly adjusted adjustable unit.
Here is a picture of the lead weight:
But it gets worse. Once we got the transmisison out, we saw that they had not replaced the top two bolts that hold the bell housing to the block. Needless to say, I will not be going back to that shop again.
We replaced the clutch with a steel flywheel and a custom made 11" metal puck clutch. My clutch cable was kinked, so we replaced it with a new cable and installed a Ford Racing clutch quadrant.
FYI, Bellhousing to block bolts are part number W500523-S439 and the starter bolts are part number W506510-S437M.