datsunan Posted November 17, 2005 Share Posted November 17, 2005 So my CF II clutch could not hold the hp of my turbo L28 so I bought a XTD clutch that was good for 400hp. The clutch pressure is slighty heavier now. I am having problems with shifting at high rpm. Someone said that maybe the slave and master cylinder are not big enough to open the clutch all the way. Has anyone else had this problem? It shifts ok at lower rpm and at idle so I'm not sure thats it. Any other thoughts. Yes I bled the lines. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 17, 2005 Share Posted November 17, 2005 When I put my ACT pp on I lost the slave cylinder within 3 days. If the master or slave was even remotely weak your new heavier pp will sent it to an early grave. Replace both master and slave and you should be good to go. You might also want to take a quick look at the shift fork. They tend to split where the pivot ball is with really heavy pp's. Quote Link to comment Share on other sites More sharing options...
john kosmatka Posted November 17, 2005 Share Posted November 17, 2005 Yeah I remember reading posts a while back I think jersey had problems with the fork splitting. I guess it goes with saying that if your using a heavy pressure plate, your best off getting a fresh slave, master, and fork. Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted November 17, 2005 Share Posted November 17, 2005 i would like to know what are the best bolt on upgrades we can do for our cars that have heavy duty clutch kits. i have the spec stage 4 un-sprung with a 10lb flywheel, i need a new slave cylinder but i dont want to just get a reg 280zx n/a unit. i rather do a upgrade now then later.. mike Quote Link to comment Share on other sites More sharing options...
rudypoochris Posted November 17, 2005 Share Posted November 17, 2005 I wish i could afford a hydraulic t/o... you guys with heavy pressure plates might want to look at that, it gets rid of the fork altogether and frees space for the exhaust. Quote Link to comment Share on other sites More sharing options...
datsunan Posted November 17, 2005 Author Share Posted November 17, 2005 This is my 2nd slave since building my car 1 1/2 yrs ago, it might have 10k miles on it. The master was also new when I built it, I'm not so sure thats it. The only other thing I did was to change the gear oil in the tranny, I used mobile synthetic 75w-90, maybe its to thick and causing problems with the syncoes (sp ?). Is ther a way to test the sycroes, someone told me if I shift the car without the engine on then start the engine and shift, if its easier to shift with the engine off then the syncoes are going out.? Quote Link to comment Share on other sites More sharing options...
johnc Posted November 17, 2005 Share Posted November 17, 2005 Grassroots Motorsports recently had a good article on clutches and pressure plates. You might want to find it because it explains why you're new system is having trouble with high rpm shifts. Annular clutch release systems are very common on racing 240Zs and typically run from $400 to $800 depending on whether SAAB or Tilton cylinders are used. I just finished setting up this Tilton 800 clutch release on a GForce T5 that's being installed in a vintage racing 240Z: Quote Link to comment Share on other sites More sharing options...
datsunan Posted November 17, 2005 Author Share Posted November 17, 2005 Thats a really nice set up, but I'm getting tired of chasing down weak links and spending money replacing new parts, I just want to drive! When will it end? I have other cars waiting to be restored and I'll never get to them if I keep having to spend my money on this money pit! Sorry need to vent. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 17, 2005 Share Posted November 17, 2005 I'd be interested to hear how a heavy pp can influence high rpm shifting John. Seems to me the only way it could is if the shift fork were BENDING. Otherwise regardless of the size of the master and slave, as long as the seals in both held the fluid is not compressable, so it should still completely disengage the clutch. If the clutch is completely disengaged then the trans should shift smoothly, and if it doesn't then the problem is synchros in the transmission. Again, unless something else is giving, either the fork or the master or slave seals. By the way, is that YOUR vintage Z that's getting the T5? That puts you in CP3M, correct? Quote Link to comment Share on other sites More sharing options...
johnc Posted November 17, 2005 Share Posted November 17, 2005 Is ther a way to test the sycroes, someone told me if I shift the car without the engine on then start the engine and shift, if its easier to shift with the engine off then the syncoes are going out.? Don't listen to that someone. Looking at your sig its pretty obvious that your transmission is the next big weak link. Heavy clutches (large MOI) put a lot of strain on the synchros (the syncro has to slow down the transmission gears and the clutch) and they slow down the shifts. You're just going to have to be more careful shifting until you can afford a transmission and clutch that will handle 400hp. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 17, 2005 Share Posted November 17, 2005 I'd be interested to hear how a heavy pp can influence high rpm shifting John. I said "heavy clutch" not pressure plate. The clutch is splined to the input shaft so it adds to the MOI in the transmission during the shifts. That's one reason why small OD multi-disk clutchs are actually easier on a transmission then larger OD single disk clutches. By the way, is that YOUR vintage Z that's getting the T5? That puts you in CP3M, correct? No, its for a customer's car and yes, it runs CP3 Mod. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 17, 2005 Share Posted November 17, 2005 I think you're taking him too literally John. I don't think he means the pp or the clutch disk weighs 20 lbs, I think he means that it has a lot of clamping force. The clamping force shouldn't change the way the transmission shifts, assuming the clutch linkage and hydraulics are working correctly. If the disk were heavier, yes, it would shift slower for the reasons you stated above. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 17, 2005 Share Posted November 17, 2005 OK, I wasn't trying to solve the problem, just providing information and I didn't confuse "heavy" with the pressure plate force. Its very difficult to solve clutch problems over the internet but here are a couple things to check: 1. Extra-stiff pressure plates often overpower the slave cylinder or even the master cylinder. When shifted rapidly, the fluid simply bypasses around the piston and insufficient fork movement is the result. In addition, at high speed, if there are add-on weights on the diaphragm fingers, they significantly increase the load on the hydraulic system. 2. In an effort to beef up the friction surface, manufacturers add extra material to the clutch disc. This can cause a problem because there's normally a slight air gap between the flywheel, clutch, and pressure plate. There's only so much room on that area. When the clutch disc is thickened, it can drag slightly even when the clutch is fully depressed. 3. A thicker clutch disk also might reduce the mechanical advantage of the clutch fork, making shifting more difficult. Quote Link to comment Share on other sites More sharing options...
260DET Posted November 18, 2005 Share Posted November 18, 2005 Nothing to do with what oil is in the gearbox? I suspect that Nissan syncros are a bit particular in the oil department, you can beat them if you shift too fast and/or the engine revs are not well matched when shifting at high RPM. Just starting to look at this, drained the full synthetic Castrol Syntrax out and have replaced it with non synth Shell 80W gearbox oil. See if that makes a difference. I know that the Skyline boys swear by Redline Shockproof in their boxes. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 18, 2005 Share Posted November 18, 2005 I think the clutch manufacturer would be fairly incompetent to put a clutch disk in that is so thick that it can't disengage. I still think you're looking at a fluid leak, broken fork, or bad synchros. I agree with Richard that lube can make a big difference. I assume you're using a T5. If it were a Nissan transmission I'd recommend SWEPCO 201, but I think some of the T5s take ATF??? Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted November 18, 2005 Share Posted November 18, 2005 If you still have the Centerforce Shifting fork and collar in the transmission. You need to replace the collar with the longer version. For some reason the centerforce clutch had to have this (shorter version) to make it work. How do I know about this. Because I had it happen in my Z. Had the Centerforce clutch go bad in my Z. When I replaced it with a stock heavy duty part from nissan, the transmission all of a sudden started shifting real hard. It seemed like the clutch was not totaly releasing. I tried bleeding and adjusting the rod with a longer rod. Nothing seem to work, so I did some research and found out that there is three different size collars out there. I put in one that I got out of a car I was stripping and it fixed the problem. The car now shifts like it should. Quote Link to comment Share on other sites More sharing options...
datsunan Posted November 18, 2005 Author Share Posted November 18, 2005 Hey redneck, this clutch came with a new TOB and it looked very different then the stock one which is what I was using for the CF. I used the same colar that I used on the CF. I think the colar I used was from the bw t5 that I am using and I remember that the other 5spd I had used a shorter colar. The long colar worked fine with my CF, althought when I pulled my CF and disk out I noticed some wear on the springs for the disc where something was hitting it, the bolts on the FW also had marks on them on the outer edges where some thing was hitting them. Originally I thought the springs where hitting the bolts but I just went out and looked at it and the spings are on the PP side of the disc. I looked at the PP and see marks on the weights located on the PP fingers. So it looks like the wieghts were hitting the disc spring and possibly pushing them into the FW bolts. So I guess I had the longer colar in there already and that screwed up my old setup but is it right for my new one? What tranny did you get your colar from ? Someone told me that if the clutch is pushing in to far you can have problems with engagment, he said to try and shift with the clutch to the floor and again with it most of the way down to see if thats the problem. I can't feel a difference. I'm going to start with the easy stuff and change out the gear lube, bleed the clutch and maybe make an adjustment to the peddle. John, what are my options for a better tranny and how much more do I need to spend? I am using the BW t5 from an 83 turbo. I saw a BW tranny out of an 03-04 mustang that looked similar to mine, don't know if the bell housing could be swapped and the shaft turned down to fit the crank pilot. ? Thanks for all your input guys, I think I'll make another donation! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 18, 2005 Share Posted November 18, 2005 Uh, I just want to make sure I have this right. Your springs were facing the pressure plate, not the flywheel? And when you pushed the clutch pedal it forced the pp spring weights into the clutch disk springs, then that forced the clutch disk into the flywheel bolts? Is that correct??? If so, you've got your clutch disk mounted backwards there datsunan... that's probably your whole problem. The springs go towards the flywheel. If you have them the other way, then the springs could be interfering with the clutch disk (like your old one) and that might prevent the clutch from disengaging all the way. You must have been flexing the hell out of the disk in the old setup to cause it to bend far enough for the flat side of the clutch to hit the flywheel bolts. EDIT- I don't think it's possible for the clutch disk to have hit the flywheel bolts if you had the disk in backwards. That would be a hell of a lot of flex. Leaves a bit of mystery as to how the flywheel bolts got hit and what they were hit by. Quote Link to comment Share on other sites More sharing options...
datsunan Posted November 18, 2005 Author Share Posted November 18, 2005 No I had it in right, theres no way to put it in with the spings facing the FW. The FW bolts are even with the FW surface leaving no room for the 1" of depth the springs would need, besides, the disc is marked "this side toward FW" on the side opposite the springs. The sping side you see in the pic fits into the center of the PP. Thats the only way. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 18, 2005 Share Posted November 18, 2005 OK, guess I was wrong on that one. I seem to remember my clutch disk fitting in the other way... it's been a couple years though. Quote Link to comment Share on other sites More sharing options...
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