Engine/Transmission (1998.5 - 2002) Issue 38 "Clutch Life"

[Gary - K7GLD]

"Lugging" isn't purely determined by engine RPM - but is a combination of engine speed vs load - and sometimes by rate of accelleration... You might idle along in 3rd or 4th gear at engine idle RPM with NO problems in heavy, slow traffic situations, or sight-seeing - but try to accellerate rapidly, and THEN you'll likely be lugging severely!



I've idled my truck slowly of 8% grades in 3rd gear in isolated mountain roads as we admired lovely mountain scenery with NO discernable stress upon the engine, as it burbled along quite happily - and still had excellent accelleration ability from that speed as needed.



Lugging is operating the engine down at RPM that causes the engine to labor noticeably, and either makes it difficult to maintain speed or accellerate in a reasonable manner FROM that RPM/speed...

 

[Wheaties]

I agree with Gary. The definition I have heard (here on the TDR and elsewhere) is that lugging is running the engine at a load and rpm such that it cannot accelerate, or worse maintain rpm. I do it too! It is fun to let the truck take itself across the parking lot at idle, hardly any stress on the engine at all. In fact, I think I heard two cylinders say to the other four just the other day, "Don't get up, we have it... !"



If you look at the torque curve on the Dodge sales literature, it says the engine can deliver something like 300ftlbs at idle! This is more than a lot of clutches ever see, let alone from a standing start. This kind of power has to be hard on it!



Matt

 

[Mschevey]

I agree lugging is based on RPM and LOAD. When I am driving in general driving conditions with only a loaded tool box across the bed, I try to keep the RPM's over 1500.



I also only use the clutch when starting out. It does not grind at all and is very easy after a little practice to find the RPM marks. Down shifting without it takes more work but works well with some practice.



NOTE: I don't recommend people who have never done this learn on this these transmissions.



Shifting this way has to put less wear on the clutch disk, but it may put significantly more stress on other parts if not done smoothly.



Mike Schevey

 

[Pit Bull]

Originally posted by Gary - KJ6Q

"Lugging" isn't purely determined by engine RPM - but is a combination of engine speed vs load - and sometimes by rate of accelleration... You might idle along in 3rd or 4th gear at engine idle RPM with NO problems in heavy, slow traffic situations, or sight-seeing - but try to accellerate rapidly, and THEN you'll likely be lugging severely! Lugging is operating the engine down at RPM that causes the engine to labor noticeably, and either makes it difficult to maintain speed or accellerate in a reasonable manner FROM that RPM/speed...

Good explanation Gary. I have not lugged mine and don't want too. It helps when your driving a ETH/DEE and it only weighs 7000 lbs with you in it

 

[JHerrlich]

Whew, I'm glad I don't have any of those springs in my clutch... Just one less thing to worry about. I don't lug it and burp the throttle when I downshift too.

 

[South Bend Clutch]

Here is also an example of lugging. Say you are cruising down the highway and you have cruise control on. You hit an incline in the road and you got a pretty good load behind the truck. The incline does not have to be that great but the truck starts to slow down. You don't catch it in time and the truck starts to chug before you catch it and down shift. At this point you do not have the rpm's high enough and the torque to great which is causing the chug. The chug IS the clutch disc (dampened portion) collapsing. This is what Andy was trying to explain. Same thing with trying to start out in to high of a gear. When you feel the chug, this is what is happening. Down shifting is something we know needs to be done but like some have said above, properly done will help relieve the stress it gives the clutch disc but if you here the rpms rise when doing this you are definitely working on the spring assy. of the disc.



I hope this helps, it is hard to write everything but if you have any questions feel free to give us a call and we will give as much time to you that is needed.



Peter

 

[RJOL]

Good to hear from you, Peter.



I guess the main question most of us have is how much shorter life can we expect if we do downshift, or start off in 2nd gear (not towing) in our trucks with 4:10 gears. Are your clutch upgrades any less susceptible to the problems discussed in the article?

 

[South Bend Clutch]

I would say that the 13" clutch is more suited for this kind of work the the 12 1/4" design.



Peter

 

[Sled Puller]

Originally posted by esommer2500

I normally shift without the clutch going up between 3 and 4, and then between 4 and 5. Downshift without the clutch between 5 and 4, and bump 4th out without the clutch while braking. I normally start in 2nd on flat or downhill, and really only use 1st when towing or starting up a steep hill. I found the article interesting, but don't think that I will take the advise given. I would like to think that my personal driving habits are pretty conservative on clutch wear of both clutch surface as well as the springs. Only time will tell.



Eric

They may help the clutch, but you are destroying your transmissions synchronizers.



These synchros are absolutely not designed for clutchless shifting.



I too enjoyed the article, very informative. I think most of us know what to do to get long clutch life, but the happy pedal does not let that happen!:{

 

[THancock]

JTroiano, reving the engine while the clutch is in does bring the rpm's up to match the clutch engagement for the higher revs the lower gear needs. Double clutching brings the rpm's up to match the gears before the shift, which is easier on the transmission. Two totally different things, one's easier on the clutch and the other is easier on both the clutch and trans.

 

[Pit Bull]

Originally posted by South Bend Clutch



Down shifting is something we know needs to be done but like some have said above, properly done will help relieve the stress it gives the clutch disc but if you here the rpms rise when doing this you are definitely working on the spring assy. of the disc.

Thanks Peter, I try to alway give it more fuel to match the rpm's when I down shift so I don't get the RPM spike. This has been a good thread and reminded everyone of what they should be doing. Now if they don't I guess they will be calling you sooner rather than later to buy a new clutch

 

[rubberneck]

I dont know about clutch life cause i still haven't broken the thing, but i can tell you a quick way to wear out the factory michelins. Add 400 hp, put in CON FE, rev to 2500 rpm, put trans in 3rd gear, let the left pedal fly, watch the smoke. pretty cool.

 

[Steve Campbell]

Peter, I thank you and Andy....

for what your intention was here, To help us all get "more" life out of the clutch. For someone who sells clutches to make a living to put that information out there is first rate in my book!!!

 

[BPINE]

Re: Peter, I thank you and Andy....

Originally posted by Steve Campbell

for what your intention was here, To help us all get "more" life out of the clutch. For someone who sells clutches to make a living to put that information out there is first rate in my book!!!

Nicely said Steve, thats what South Bend clutch is all about I have found out over the years. There is no one clutch that fits all and education on which one and how to use it is always a priority at South Bend Clutch. If you need a pulling clutch and called them I think you would be surprised at the answer you got, they are not afraid to send you in the right direction.

 

[Rockcrawler]

More theory and direct experience...

My O1 5sp is mildly warmed at about 300/700. I just had the stock clutch replaced (used a stock 12v clutch as recommended by several TDR popular shops for my application). The clutch was replaced for no other reason that the dealer was in there to give me a new SB at 69k due to the 8" crack in the 53 series block. (New SB is a 56 series)



Half my miles are towing something, since i bought a quiet family car last march the truck is almost always towing, grossing 15-20k depending on which toys etc.



On the stock disc, the support pieces, which are prone to contact and wear when the springs compress, are symetrical, that is equal "cushion" using fwd or reverse. In the article these pieces were skewed to give more cushion in the forward direction.



I'm also 355'd and 33" tires, a second gear starter unless towing or on a hill and I down shift, with an ex brake and never thought twice about aggressive downshifting coming off an exit ramp. The Fwd motion side on these posts showed clear evidence of contact with the mating surfaces worn about . 010 and . 020" respectively. No danger of compromising the disc though IMO.



The reverse side showed no evidence of contact though it may have at some time- no visible wear. As a techie, it's hard for me to imagine the torque from aggressive downshifting even with my ex brake being any harder on it than backing up a slight incline, with a heavy gross and initially engaging the clutch from a dead stop at the approximate 5/1 reduction in reverse- a lot of inertia absorbed in this example. Based on the lack of wear I am quite comfortable to continue my down shifting habits, even loaded heavy and with ex brake.



The reason people gave me to go to the 12v clutch was the springs. The longer, maybe skinnier springs in the 24v are prone to dislodging/breaking etc. One of my six outer springs had the internal one broken, the short piece turned sideways and was preventing the outer spring from seating by about 1/4".



FWIW, wear on the disc at this point was about . 030/. 040 from the closest rivet. The rooving in th lining was starting to dissappear in random fashion, though the grooving was about 95% there.



The pilot brg was bad- I did not get to see it- the tech said he could not be sure if it was bad or damaged in removing the engine. I'm pretty religious about sitting at lights in neutral with the clutch out.



Clutch problems, based on the broken spring, were likely not far away. A lot of my towing is 19-20k through 40 west, colorado, utah etc. Truck pulls hills real well, set cruise at 7-8 over posted limits (=78-83 towing speeds). I've never felt or noticed clutch slippage, always downshift at 15-1600 rpm, which is not required very often at all.



I'm pretty sure I've read on several occasions from good sources - one being new venture that shifting the NV4500 without clutching is real hard on parts and will kill the transmission.



Hope this info helps others, great thread!

 

[DEZLPWR]

Double clutching....

I have heard that it is good to double clutch... . Would someone please explain what it is, why it is good, and a step by step process for doing it?

 

[South Bend Clutch]

DEZLPWR,



This was a post on the Dodge-Diesiel.org site about the same issue and artical.





"ASFMSgt as long as your driving a synchromesh transmission you will never need to learn, find your RPM split on the upshift and reverse it for the down shift. Double clutching is the taught method of shifting a NON-synchro transmission with straight cut gears. Start by finding shift point push in clutch take transmission out of gear to N push clutch in again put into next gear, basically 2 clutch movements 1 gear change. Reverse this along with down shift method stated before and you have it built--- theoretically of course, perfecting this with a real 9,10,13,15 or 18 spd takes a little more time. Start adding a second transmission and you can really have some fun. PK"



I hope this helps,



Peter