Will a lighter flywheel and clutch assembly be easier on a transmission? I picked up a 5 speed not rated for the engine I have built. I have a 3 disk 7" clutch that uses a flex plate. 12 lbs total.
Will a lighter flywheel and clutch assembly be easier on a transmission? I picked up a 5 speed not rated for the engine I have built. I have a 3 disk 7" clutch that uses a flex plate. 12 lbs total.
Probably not, more likely it will be harder on the transmission. A clutch disc with spring hubs and marcel carriers would be better. Edit: I went through this with my 81 Camaro CP car, the clutch was just a bit too harsh for the ST-10 4-speed.
stan_d wrote: Will a lighter flywheel and clutch assembly be easier on a transmission? I picked up a 5 speed not rated for the engine I have built. I have a 3 disk 7" clutch that uses a flex plate. 12 lbs total.
There's a good chance that your new transmission can handle your engine's power, but an aggressive clutch can draw additional inertia energy out of the engine's rotating assy, adding extra torque to the transmission's input shaft. You will need a clutch that can tolerate some slip if you are trying to protect the transmission, but I doubt that a 12lb clutch/flywheel assy will be able to slip very much without overheating. A heavier clutch assy with less torque capacity and more thermal capacity would probably serve you better.
Ideally, the clutch's holding power should be matched to the power you make with very little reserve. Here's a simplified explanation- let's assume the engine makes 500ft/lbs and the clutch's capacity is 700 ft/lbs. When you launch the car, the clutch is going to draw 700ft/lbs…the 500ft/lbs that the engine is making at wot plus another 200 ft/lbs of stored inertia energy that will cause the rotating assy to lose rpm. That extra 200 ft/lbs makes the launch more violent, but as soon engine rpm is drawn down to the point that engine rpm sync's up with vehicle speed, rpm ceases to drop and that transfer of an additional 200ft/lbs of inertia energy stops. The downside is that after you have lost the rpm and used that inertia energy, that spent energy then has to be paid back in full before the engine can recover the rpm that it lost. That inertia energy transfer which made the car launch harder initially now slows the car, as it reverses and some of the engine's power must be used to recharge spent inertia energy back into the rotating assy. In the end, that temporary 200 ft/lb boost did not actually net you any performance gain.
Why subject your transmission and drivetrain to that extra 200 ft/lbs if it doesn't net you anything? What if that extra 200 ft/lbs of holding power gets you a broken transmission?
If a clutch with only 600 ft/lbs of capacity were used it would slip roughly twice as long, which means the car would be traveling faster at the point where rpm and vehicle speed finally sync up...less bog. Not only does the transmission see less abuse, but the engine doesn't lose as many rpm after launch and after the shifts...the engine will be pulling from a higher average rpm where it makes more power.
stan_d wrote: Will a lighter flywheel and clutch assembly be easier on a transmission? I picked up a 5 speed not rated for the engine I have built. I have a 3 disk 7" clutch that uses a flex plate. 12 lbs total.
For high RPM launching, it'll be easier on the trans.
If you have an engine that bucks and snorts and has part-throttle power delivery like a jackhammer (wants to find all of the lash in the drivetrain), transmission life drops markedly with a light flywheel.
In reply to weedburner:
Isn't that the idea behind the "soft lock" clutches you can buy, or the redneck version of mounting a screen door shock to the pedal?
BrokenYugo wrote: In reply to weedburner: Isn't that the idea behind the "soft lock" clutches you can buy, or the redneck version of mounting a screen door shock to the pedal?
The SoftLoc style clutches have a centrifugal component that adds clamp pressure with rpm. Engagement might be soft on launch, but very harsh after a WOT shift.
I'm the guy that invented the screen door style clutch buffer. It softens engagement both on launch and after all shifts made using the clutch. Very popular with NMRA's manual trans Coyote Stock and Factory Stock guys. Here's a link to a page that explains the screen door style clutch buffer and how they work... clutchtamer.com
Do you gave challenge car pricing on the clutch tamer ?
How about a budget friendly DIY version?
It's not as compact, but just as effective if you have the room.
Nice explanation. You know clutches.
To address the original question, directly speaking, no, the transmission doesn't know or care about the flywheel.
But how you drive the car could affect it. A lightweight flywheel can, in super scientific terms, be more jerky which would stress the trans more. :)
But the error weedburner makes is that the driver is the sole determinant, through throttle and clutch application, of the torque that is applied to the transmission. Unless you're talking rev-limiter clutch dumps where there is no modulation.
But that aside, you can in theory drive either smooth but less flywheel mass would make it more difficult.
jfryjfry wrote: But the error weedburner makes is that the driver is the sole determinant, through throttle and clutch application, of the torque that is applied to the transmission. Unless you're talking rev-limiter clutch dumps where there is no modulation.
I find it's more fun when you are able to drive it like you stole it 
stan_d wrote: Do you gave challenge car pricing on the clutch tamer ?
Nitrous jet, a line lock, and some misc. fittings/tees
The nitrous jet is the calibrated restriction so the clutch lets up at a certain rate, the line lock is so you can switch between restricted and unrestricted action.
Guy pulls 1.3 short times on short/narrow slicks.
The whole thread is chock full of low-budget performance hacks.
I always assumed the lighter flywheels I put in were irrelevant to the transmission and imapctful to the valve-train as suddenly it was the link spinning down that energy.
84FSP wrote: I always assumed the lighter flywheels I put in were irrelevant to the transmission and imapctful to the valve-train as suddenly it was the link spinning down that energy.
Transmission failures on certain cars can be traced to removal of the balance shafts on the engine!
Another thing to think about... Dual mass flywheels. Yeah they are heavy and expensive to replace, but they are effectively a harmonic damper between the engine and the trans. Change that to a solid, now the harmonics are buzzing the gears/bearings in the trans...
Knurled wrote: Nitrous jet, a line lock, and some misc. fittings/tees The nitrous jet is the calibrated restriction so the clutch lets up at a certain rate, the line lock is so you can switch between restricted and unrestricted action. Guy pulls 1.3 short times on short/narrow slicks. The whole thread is chock full of low-budget performance hacks.
Reaction time sucks using those. Launching from a full tree, you will have to leave a little earlier. On Pro Tree or arm drop/flashlite style starts, you will want something that hits a little harder/quicker.
The reason for the solenoid is that style restriction delay slows down engagement too much after a shift, so during a shift the delay needs to be disabled. But with the delay disabled, you are back to harsh engagement. If the OP has a T5, he will also want to protect 3rd gear at minimum.
With my style of buffer, there's no delay at all on getting the engine's power back to the transmission's input shaft after a shift. The delay only becomes active during the last excessive/damaging part of the engagement process. No reason not to use it during the shifts, as this style of controlled slip actually helps make the car quicker.
What if you only use the clutch to launch?
Guy I worked with had a slick shifted T5 in his Mustang. He said he just held pressure against the shifter and when the engine hit the 8800rpm rev limiter, it would pop right into the next gear, no clutch or lifting.
IIRC it was deep in the 10s, all motor and stock stroke. This was in the 90s when that was really impressive
Unless you're drag racing, you should be driving it so that the clutch doesn't cause shifting to shock the transmission at all. Either shift quicker or slower so that when you pop the clutch, the engine is at the right RPM to match the input shaft, and you have no problem.
I have learned how to shift without the clutch in normal street driving.
I will have to treat the 5 spd as glass. Also the 7.5 rear until I get the 8.8 in.
stan_d wrote: I have learned how to shift without the clutch in normal street driving. I will have to treat the 5 spd as glass. Also the 7.5 rear until I get the 8.8 in.
Be careful when shifting a synchronized trans without the clutch. The synchro blocker ring is basically a brake that matches the input and mainshaft speed. If the input shaft is still attached to an engine, then it "rides the brakes", and can wear out the friction material much sooner.
It's a good skill to have, but not the best to use all the time. Unless you have an unsynchronized transmission. Then it's okay.
Yeah it doesn't matter how good you think you are, ANY mismatch in speed trying to shift a sycnhro box clutchless is making the sycnhros work a lot harder than operating it as intended. You're asking them to (in futility) slow down/speed up the entire rotating mass of a running engine, rather than just an input shaft and clutch disc.
It's not even the rotating mass of the engine, it's the braking force or power of the engine that you're putting on the synchros. If it were just a flywheel that weighed as much as the engine's rotating assembly it wouldn't be nearly as bad.
I looked into this for directly coupling an AC induction motor to a synchronized gearbox and using clutchless, automatically rev-matched shifting. When this kind of motor is freewheeling it really is like a giant flywheel.
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