T-5 Transmission Information
The transmission used behind the Ford 289/302 engine is a fairly new Borg-Warner T-5 manual transmission. Some of the problems faced with attaching the transmission to the engine were discussed in the Power plant section in regards to the pilot bearing and engine plates. The use of a hydraulic throwout bearing and the needed modifications will be discussed here.
Being the Z cars used a hydraulic slave cylinder for its transmissions, I decided that with the lack of room in the transmission tunnel for any mechanical linkage, I would do the same for the T-5 transmission, except go one step further, and use a hydraulic throwout bearing instead. The throwout bearing is made by McCloud Clutches and slips over the snout on the front bearing keeper of the T-5. The literature included with the bearing indicated the need for a master cylinder with a 1-1/8" piston travel. Unfortunately, the Z cars use a 5/8" master cylinder with about the same travel. Well, I tried it anyway, and found to my dislike, the pedal was mushy, and full travel was needed to disengage the clutch. This is not very conducive to quick, smooth, shifts. In desperation I even tried to use a 7/8" brake master cylinder (sense the bolt pattern was the same) with both lines tied together with a T-fitting, but this was too large. The clutch pedal was now too hard to push, and the pushrod going through the firewall was bending. I was beginning to feel like Goldilocks!(one too big, and one too small). But, as has happened throughout this entire car building process, luck (very good luck) was with me. After weeks of looking in salvage yards for a larger diameter clutch master cylinder, I finally found one on a very early Datsun pickup truck (mid sixties model I've been told **) that was in diameter, and had a little over a 1" stroke (all the other ones I looked at were 5/8" cylinders) and had the same identical bolt pattern as the original Z cylinder. I didn't realize though, how lucky I had been in finding this part until I tried to replace it with a new one. No one lists a clutch master cylinder for any Datsun vehicle, not even Nissan. I even searched through over 50 boxes of rebuilt and new master cylinders at a prominent foreign car parts house, only to find they were all 5/8" bores, except for one bore cast iron cylinder used on an '86 Land Cruiser with a triangular bolt pattern. I eventually was able to use the Datsun pickup cylinder though, after some rebuilding (see note below). Anyway, with the larger clutch master cylinder in place, I connected the brake line to it and the throwout bearing with the help of some metric-to-SAE brass bushings. The clutch works beautifully!
The last thing to mention here is that the rear transmission mount is a simple steel piece I made that is bolted into the transmission tunnel using the factory transmission mounting points. The engine and transmission are now solidly bolted to the chassis at six points. This has added to the rigidity of the chassis a great deal.
Note: The pickup truck master cylinder I got from a salvage yard was in poor shape, in that the bottom of the inside bore was pitted from moisture accumulated over the years, and because of this, leaked brake fluid past the firewall seal at a slow rate even when it was not being used. As a result, I had trouble passing the pre-race inspection with all the paint under the brake pedals and on the floorboard peeling as a result of reacting to the leaking brake fluid. As I mentioned in the above article, I was not going to be able to buy another cylinder to match this one, and I wasn't going to have any better luck in finding a rebuild kit for it either. The only other option available to me, other than using the heavy cast iron Land Cruiser cylinder with the different bolt pattern, was to try and rebuild the pickup cylinder with makeshift parts (remember, I have nothing to loose now). First I used a brake hone to hone the bore (aluminum remember) very carefully so as to not remove too much material. I would not be able to remove all the pitting, but I was going to at least try to smooth the edges of the pits. Then I used fine emery cloth to complete the conditioning of the bore. I happened to have some brake master cylinder internal parts from some odd project I had earlier (don't ever throw anything away), so after comparing the rubber seals on both these cylinders, I came to the conclusion that the brake seals were slightly larger in diameter and a bit more flexible than the clutch cylinder seals. With some very slight filing on the clutch piston-to-seal interface I was able to replace two clutch cylinder seals with two brake cylinder seals that were comparable in shape and thickness in the area of the bore where the pitting was at its worse. Upon reassembly, I am happy to report No leakage at all, even under heavy use.
** As of 8/95 I finally found another Datsun pickup with the same master clutch cylinder, and found this truck to be a 1967 vintage. Now I have some solid information in which to find more like it, and at least rebuild it.