Thanks for the post Peter. I have been driving big rigs for the last 30 years and I agree with you about our trucks can't be compared to the big boys. I have read several times fellows are shifting without using the clutch and I don't agree with that either. I am running your Con-O clutch and it is a great clutch. My Freightliner is an N14 with 525hp. I need to call some day and find out if you make a clutch for it.<br>Michael

 

Ok question, Peter. Do you feel that the SBC will handle the rigors of decel if shifted properly, keeping the strain and shock of shifting to a minimum? In my case the weight is being pulled, the downshifts are necessary, and on a down shift I would never pull the gear in without matching the engine speeds. I am talking of the six speed clutch and your best.

 

one rule that ive always heard from truckers is that you always go down hill in one gear lower than the gear you went up in and is it true that downshifting is bad for fuel mileage if so then how much?

 

I was taught-same gear up or down. Most ppl just ride their brakes. Just watch. Most ppl are brain dead. Never LEARNED to drive. Automatics: the ruin of the driving public. If'n you didn't learn to drive on a stick, you probably don't know how to drive. Just me opinion. 8)

 

You can always use one of those run-a -way ramps instead of down-shifting.

 

I HUAL A BIG CAMPER,3000LBS DRY + BOAT,ALWAYS DOWN<br>SHIFT IF TACH ALLOWS,THIS HELPS EXHUST BRAKING AND<br>PREVENTS BRAKES FROM OVER HEATING ON LONG DOWN HILL<br>RUNS.180000KMS HAVE NO PROBLEMS ORIGINAL CLUTCH.

 

This is my first (as far as I know - my home 'puter doesn't do Java!) post.<br><br>I am reminded of several times in my driving life.<br><br>A manual trans vehicle with a hydraulic clutch that would leak (old Datsun PU) would sometimes have no clutch pedal. Would usually always try to park on a slant. Push it off in 2nd, and shift clutchless to where I needed to go.<br><br>A UPS Package Car back about 1988. The trans got stuck in 4th. No amount of push-pull-kick would change it. My supervisor asked if I could drive it in. I said it will kill the clutch IF I can do it. He said it's cheaper than a tow truck. I slipped the HELL out of it and got it back about 18 miles to the building. We had a ramp to go up, stop while still inclined and then proceed into building. Smoke was POURING out of my car but damned if I did't stop!<br><br>My current 1990 F-350 CC 7.3 Non Turbo with E4OD. I pull about 3500# about 75 miles around once a week. No trailer brakes. I pull out of OD, and I downshift to help out my brakes.<br><br>I hope to own a second gen 12v Cummins powered D-250 in around 6-8 months. Got to see how things go.<br><br>My buddy has a 1991 Regular cab CTD auto, and a 2000 Club Cab auto. We just did Chicago to Houston in the 2000 with approx. 6000# in addition to the truck and trailer . We were towing at an average speed of just over 63 mph in OD. If it were MY truck, we wouldn't have done it in OD, but the truck stayed at at least 1800rpm an any hill I saw and shows no ill effects.<br><br>I probably won't post much here, but if it's something I know something about, you'll hear from me!<br><br>

 

Great post y’all, I thought I knew how to drive and still learned some thing’s. I also would like to read Peters thoughts on H.I.D.’s last post. Thanks for all the info.If it will make you feel better H.I.D., just because you don’t have hair or teeth that don’t make you an old phart. It’s all in the mind …….I hope.

 

[quote author=SeaRay88 link=board=11;threadid=6817;start=30#69008 date=1037677017]<br>I was taught-same gear up or down. Most ppl just ride their brakes. Just watch. Most ppl are brain dead. Never LEARNED to drive. Automatics: the ruin of the driving public. If'n you didn't learn to drive on a stick, you probably don't know how to drive. Just me opinion. 8)<br>[/quote] <br><br>Very untrue being in the business for 30 years..Ive seen the ladys that start driving the big rigs...and put the men to shame...one little lady 4'10&quot; tall never drove a gear shift in her life...until she got a CDL...I road tested her fresh out of school...best gear graber Ive ever seen never ground one gear ...BUT BEING SO SMALL she couldnt crank up a loaded trailer if it was parked with the landing gears low...even I couldnt shift as good as she did ( of course she was only one person)...and remember alot of these PRO drivers we have on the road now cant even tell if the brakes are adjusted correctly to stop their rigs in time on a downgrade hill...their answer is IAM NOT A MECHANIC....ok Iam off my soap box for now

 

Peter from SBC could you please explain what on these clutches that you say are failing and what was the actual cause of failure. I have seen in large trucks where big power was abused and the clutch centers were torn out, have also seen this same problem occur in the CTD. A clutch disc is simply a splined yoke attached to a metal disc usually by rivets, a riveted/bonded friction compound on both sides of the outer disc which the pressure plate clamps between it and the flywheel. Unless excessive slippage from riding it trying to move or improper shifting up or down the disc becomes clamped good to a certain amount of pounds of force and is designed for X amount of foot pounds torque. By pulling with 300HP/600FtPds torque and switching to a retarding torque 160HP/400FtPds by removing pressure from the throttle trying to decelerate I cannot see a clutch failure resulting from this. I have yet to see component failure even on vehicles large or small HP increased or not with a good smooth and consciencious driving method. My trucks are not abused but well used, the CTD's are subjected to loads up to 25000 lbs gross and the class 8's have pulled up to 425000lbs on 196 wheels. Not trying to be a wise guy as I have already posted on clutchless shifting, dont race the trucks unless on a mountain grade pulling but I am looking for a explanation of your view as I have never experienced a clutch failure unless I got rammy. It should be noted that long before anybody built high torque spec equipment the big boys pulled big loads with some pretty wildly enhanced power units eg;3406's at 540/2000+ torque- 3408-V8's at 780/2400 rwhp. Most of the component failures we had were on the 3408's as the torque rise comes up faster than the 6's and if you don't featherfoot it the clutch centers or the input shafts would break. Again this is a driving technique generated through experience and &quot;feeling the power&quot; and knowing when to make adjustments on the foot feed to prevent destruction. When dragging large weights around you become more patient in driving because driving takes constant planning, if this carries over into everyday driving habits especially in traffic you will become a smoother driver and kill less parts. PK

 

Haulin in Dixie,<br><br>Properly done, no there should never be a problem. Which brings us to P Kennedy's post which relates to the same subject. Now this is only one case of all the clutches that I've had dealing with the 13&quot; design, but I had a guy call me that had ripped the center portion out of the clutch disk at this point. Picture 1 He actually seperated the clutch facings from the dampened portion of the clutch disk. I asked him what had happened and he said he was just driving along. : After I hung up on him three times, his 4th phone call said, ok, I was pulling a heavy load on an upgrade and missed a couple of gears. The truck started lunging severly and I let off. Then nailed it again in the proper gear but the truck would not go forward. I don't think I have to explain what happened. But we were then able to talk better. LOL<br><br>This is a picture of the drive side of the stop pin being hit in the 13&quot; design. Picture 2 Then you have the non-drive side of the stop pin being hit as well. Picture 3 Looking at the whole clutch disk Picture 4 you can see how far the hub has to travel on the drive side (right side of the stop pin) to hit the pin. What happens at this point is the spring is collapsed to the point of taking the coil out of the spring thus giving the spring a shock. If this continues a very long period of time the spring will eventually break. Under normal driving you will not see the stop pin being affected, it is only when it is overloaded. As for the other side, the only way that it can hit that side is reverse torque. It does not compress the spring completely to reach this point but is working the spring back and forth thus creating more wear. Again, properly done (downshifting), this will not be a violent action. With this picture Picture 5 you will see the 12 1/4&quot; clutch with significantly more damage to the stop pin. This cause is due to the size of the dampened center. The springs are not as strong and the travel is not as great therefore failure will occur at a much more rapid rate to the point of destruction. Picture 6<br><br>With the older semi's the original designed clutch was a double disk ridged setup just like what is used in the sled pulling clutches for your diesels today. The problems that occured with them was the ridgidity of the hubs causing damage to the input shaft with wear to the spline or input shaft breakage. Also, there was breakage to the clutch hub disk and at times, we saw the splines completely gone out of the clutch disks. They then designed what they refered to as a spine saver. This was a long, independent hub, that slid over the input shaft and the hub was splined on the outside to accept the clutch disks (double hub or spline). This worked well to save the damage that had occured previously but problems that still continued were harshness of engagement and the overall damage done to the transmission through shock so they then designed the spring loaded disks. This worked very well to save the input shaft from failure or wear and gave extended life to the transmission. The problem was, the springs were still in a ridged state with the torque applied one way or the other. Through the vibration of the engine and the torque loads the spring life was not long. So they finally got smart and designed the spring to fit the disk like this: Picture 7 What you're looking at is the spring does not fill the window that it rests in, thus allowing the center of the clutch to oscillate. This is called free travel. Now you have a clutch that can handle the vibration caused by the diesel, torque and spiking action at the crank related to the diesel. This is a picture of the disk assembly. Picture 8 We have conformed this disk to fit the midsized trucks and are using it in the 6 speed power strokes. With a few more modifications, this might just be our upcoming disk for the dodge applications.<br><br>I hope this helps.<br><br>Peter

 

Peter, I guess its not a good thing to gear down to lock up my duallies and put the truck into a spin then huh? <br><br>Great Pix and explanation. ;D<br><br>Still waiting for that 18&quot; Yugo clutch.

 

Thank you Peter for posting an explanation that uses logic and explains what does happen. No where do you say that &quot;proper&quot; shifting up or down will kill your clutch, however it does explain to those that don't use a clutch for shifting, it can cause damage by not shifting smoothly. There was another post which said that Road Ranger transmissions were to be shifted without the clutch, sorry wrong info the Eaton brochures say &quot;may be shifted clutchless&quot; but they recommend using the clutch especially when switching ranges. Improper shifting with or without the clutch is as Peters testimony and pictures show detrimental to the clutch and downline components. One of the things we were taught was a transmission properly shifted can be done with 2 fingers on the top of the ****, any more pressure than this and excessive force is being applied. This was demonstrated with a transmission that was cutaway to show how the forks moved the gears inside. Add 3' of gearshift with 200lbs attached to it (the driver) and inexcess of 600ft lbs of torque is being applied to the shift forks- (force shifting). Another thing I have seen while being a driver trainer is the operator completely releases the throttle when shifting up, those that learned to drive on Cat engines will rock back on the throttle but maintain some pressure (rpm) on it. Only experience can teach you this method of smooth shifting, it is not going to be perfect the first day as many truck drivers have discovered. All three fuelling systems on the CTD can be shifted effectively this way up or down but one must study the gear splits. Bottom line is your clutch is taking the beating in all this when improperly managed with residual damage down line in the driveline. Peter hopefully with these postings the number of clutch failures presented to you created on flat land driving down the highway will go away?????, okay so that might be dreaming. Sorry I had to bait into this explanation but misinformation is unfair to those that don't know any different and want to learn, Thanks again great presentation. PK

 

I will say that clutchless shifting if done properly will have no effect on the clutch itself (flat road!!) but I do believe the long term affect on the syncros will take its toll. Will it save the clutch? I would rather put a new clutch in after 100,000 miles then have to rebuild the transmission after ..... miles.<br><br>Your call, your truck. <br><br>Peter

 

Peter,<br><br>Thankyou for the very unbiased response. To do the work that I must with the CTD, downshifting is a must and I do accomplish this with the LUKGOLD clutch at this time. Of course this clutch is only 30 some thousand old, but the original clutch had 126 on it before the center went out. After reviewing the pictures I need to dig the old clutch out of the junk pile and look at the pins but there is a problem. How mine went out was that it started shifting poorly, finally getting to the point where I could not release the clutch. This was on one load, not a long problem. The idea was to get home. Having done that before in other situations, I started the truck in gear. Thought I was going to make it home, as I was 200 miles away. Of course this is really destruction to the clutch center. It gave away with a large crunch. If I had to do it over again, I would do the same. It took me two days to retrieve the truck, the trailer and the load. I might have made it.<br><br>The condition of the clutch was excellent except for the center, which disintegrated. The input shaft was good; the pilot bearing was pushed into the flywheel where no contact with the pilot was possible. In the first picture of the bad clutch the facings look to be seriously burned, so this was a very mistreated clutch. I have never had a condition like that on any clutch. As a matter of fact, on an old 238/RTO13 I had put in a new clutch, center plate and reground flywheel. After over 400,000 the pull type release bearing went out, yeah clutchless shifted from Seattle, and you could still see the grind pattern on the surfaces of the center plate, flywheel and pressure plate. I am easy on a clutch and on the 13, never used the clutch once moving.<br><br>Sometimes on the CTD on flat easy driving, I clutchless shift, and as mentioned that is a one or two finger deal, but on a hill or where aggressive shifting is necessary, I double clutch. Any driver that says that he never shocks the system is untruthful, but I normally do not. As a matter of fact I can just about tell you how we broke the original clutch. I mentioned this in another thread and now am very careful of this. I pull into a truck stop, the last fueler spilled fuel all over, and I get into the truck push the clutch and put it in gear. About this time my fuel coated shoe slips off the clutch. With a loaded trailer behind me and brakes on, the truck lunges at the full power of the Cummins, takes a second to respond and correct the situation. It amazes me that this had been done I think three times, twice by me and once by my son (that he admitted!), and the driveline is fine. Like the T-shirt says, XXXX happens! You fix it and go on.<br><br>I am sure that your best clutch is much stronger than the original, so it should be more than strong enough. If I should break it as I mention above, I have to work it out. Again I appreciate the responses. After Christmas stuff is over I will be calling to set up a purchase. I had intended to install the six speed over the holidays; my life is a nightmare of constant goings here so it has to wait a bit. Thanks again,<br><br>Bill<br>