Clutch install tip's??

[NIsaacs]

If you click on the link and scroll down the page to Note: it recommends not down shifting because it is hard on your clutch?? How can you tow, use your exhaust brake and not down shift? I have never heard of this and will ignore it Am I all wet, any comments?

Nickhttp://usdieselparts.com/

PS: Dang it, the link is not quite right. So here is the quote: "It's very important to break in your clutch with 500 miles of stop and go driving before you pull a load. Your clutch will last longer if you avoid down shifting whenever possible. Down shifting flexes the pressure plate causing uneven wear. Just remember, use your brakes instead, they are cheaper to repair." Huh??

 

[Woodenhead]

Crazy talk, ever heard of a clutch failing prematurely from down shifting? I guess anything is possible if you're hard enough on the equipment. I down shift and use my exhaust brake most of the time when unloaded and all the time when loaded. I do tend to double clutch to save on synchros and always keep the the RPMs lines up when engaging the clutch. The only time my clutch really slips much is when taking off from a stop.
To each his own I guess, just my $0.02.

 

[GCroyle]

NIssacs,

IMHO downshifting is a part of using a clutch, the question is when is it appropriate and then the drivers skill to complete a downshift. I don't have the time to try the link right now but anytime that you can minimize clutch use, up or downshifting you are saving component wear. I'm not advocating floating like big rigs. When I'm towing I'll try to anticipate the stop light as best as possible and be maybe a bit conservative.

Downshifting comments.

1. Do not skip gears, unless you have dropped the road speed enough to make that 6->4 the correct move for example.
2. Match engine RPM to road speed to minimize the lurch and taking the Cummins from idle to road speed, make it smooth.

How downshifting CAN damage a clutch.

1. Over speeding the disc at a downshift by picking up (accidently) a really low gear. Talked to a couple of folks over the years that have turned a disc into a turbine and kablooey. This was even reported years ago on European made tour busses that had like a 17" single disc (IIRC) and if you drove it kinda old school sloopy and hit the wrong gear with the syncro, over speeding and guess what, kablooey again.
2. Drive strap buckling. The drive straps pull the pressure plate in engine rotation, only mechanical connection of cover stamping to pressure plate casting. If you do a Monster downshift, the straps now try to PUSH rather than PULL the casting, straps can get bent, no more release, pressure plate position is affected might even show up as a vibration. Call tow truck.
3. Regarding #2 above in particular to cars, no need, no gain, no reason to test drive a manual trans on the rack with the wheels in the air. DON'T DO IT. Straps can really get damaged this way. If you want to test for release, push clutch pedal in, trans in gear then have someone rotate drive shaft, should have reserve release travel.

The torsion damper of lets say standard configuration clutch discs DO have a damper spring curve that is different for drive vs. coast.

Gary

 

[RikDavis]

I have always geared down. Never had any problems with the clutch however I put a Gear Vendors unit on the 99 and had all kinds of problems until the factory just happened to mention you should not do that with their unit. Who would have guessed, and it wasn't in their manual, at least back then.

 

[Tuesdak]

Even South Bend hasn't overcome or 100% adapted to engine brake use. Engine brakes were invented not to save wear on service brakes, but, to keep your speed under control on long grades where the service brakes overheated to the point of no longer working. You buy an older Dodge with a manual because the older automatics can't take engine braking without help/mods. There are places that take even modern pickup 4 wheel disk systems to their limits towing. California's Grapevine (99 north of LA) comes to mind as badly needing a engine brake in addition to just downshifting and squealing hot brakes...

Sure it adds extra strain and wear on every component. A trade off many are willing to make to have cool brakes to shut it down quick if needed like when encountering: Elk, suicidal drivers, and other misc things in your path... Something faded hot brakes can't do.

I'd like to know what "drive surfaces" are vs. friction surfaces in SB's answer. I would be guessing with their reference, but, they don't clearly spell it out as the damper or say if they mean in addition to the damper assembly.

2nd to the last question.
http://www.southbendclutch.com/troubleshooting.html
Is it ok to use my clutch as a brake?

 

[NIsaacs]

NIssacs,

IMHO downshifting is a part of using a clutch, the question is when is it appropriate and then the drivers skill to complete a downshift.

The torsion damper of lets say standard configuration clutch discs DO have a damper spring curve that is different for drive vs. coast.

Gary

Thanks Gary, I was hopping that you would respond. Anything can be broken, however in general, downshifting is not any harder on a clutch than upshifting. Again, in general, a down shift and exhaust brake use is easier on the clutch than full bore power, at say, 800 lbs of torque. It would be almost impossible to match that torque with a down shift. Yes, I agree that the damper spring curve is different for drive v/s coast, however some say that the clutch is designed to torque one way only....thats not so. They are just not that fragile. I think to say "don't down shift" shows a lack of confidence in the product.

Nick