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Discussion Starter #1
The clutch pedal stiffens up and becomes more difficult to depress after driving for extended periods of time in the same gear.


I know that I have read about this before -- is there a known issue and/or cure?
 

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It's a known issue. Mine will get difficult to depress after a highway run, but only on the first press.


I'm betting that your fluid in your reservior is black too. GM say this is caused by the 'carbon black' used in the clutch seals/parts and is normal.


Some others have gotten GM to rework the clutch line (add insulating tape) and install a tranny cooler.


I don't think anyone really knows what is actually going on. Most cures seem to point to heat at the problem, but if that is the case, why doesn't the Ford version have a similar problem?


Mine is not bad, so I'm leaving it alone...


Later...
 

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Discussion Starter #3
Thanks for the reply. Mine isn't bad either, but I am concerned about other side effects -- particularly if it is a heat issue.


A cooler and some Castrol SRF might not be a bad idea anyway...
 

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I can't figure out why heat would cause it to stiffen up, you're not using the clutch when you're staying in one gear so where's the heat coming from.. And if it's from lack of heat, why doesn't it feel like that when you first start it up in the mornings? Edited by: Camstyn
 

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I just don't believe heat is the issue either.


I'm thinking there must be some mechanical binding that happens after prolonged clutch engagement. Maybe things are just getting 'tightened' up....kinda like our oil filter



Later...
 

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Same here. Even when mine stiffens up the clutch travel remains the same. I figure if it goes then I'll know for sure what's wrong.
 

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I have never seen a 6 speed truck, I dont know of any troubles directly relating to that problem. I dont know if heat is the trouble or not, the coolest operating condition for the trans is at a steady speed. Not much heat build up going down the highway. The ZF6 comes with Transynd in it from the factory so you wont upgrade fluid by much. Is it only stiff for the first few pumps or just one pump or.....?
 

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Just the first stoke after a long run . . . probably 3 times the force normally required.
 

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Discussion Starter #9
dmaxalliTech: Thanks for your response.


If heat is an issue I would think that it would be in regards to the hydraulic-assist rather than the trans itself.


I have no idea where the heat would be coming from -- as you pointed out in your response -- there shouldn't be much on the highway.


The latest theory I have heard is that it is an issue with the "self adjust" mechanism. Whatever the case, I do believe it is likely an issue with the hydraulics.


Personally, I don't mind the stiffness, I am only concerned that it is a symptom of a problem that could cause serious problems.
 

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Joe, how's your clutch/flywheel holding up to that Quad 215?
 

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Discussion Starter #11
So far, so good, but it is too early to tell. I am being relatively easy on it in 5th and especially 6th as I would like them to last until I replace them with some stronger aftermarket parts.
 

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Just as long as don't over push your truck you will be all right. I cracked my fly wheel on my other truck because I left the 60 hp tune in one night pulling a 30 ft trailer with 15 rolls of hay and the bobcat on the back. The clutch was slipping but I never backed off till I got home. But if it ever gets that way you will literally have to stand on the clutch pedal to get it to push in.
 

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A buddy of mine is towing a 28ft enclosed cargo trailer with the Juice on the 90 horse setting, is he going to run into flywheel/clutch problems?
 

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Sorry to drag a thread back from the dead, but mine's in the dealership as of today for them to chase this problem. It's stiff for the first hit after any siginificant distance, and the first several hits after towing for a serious distance.


I just got back from a California round trip (Cali's 1200 miles each way for me) and if I ran an entire tank of fuel nonstop, the pedal would get so stiff that it'd lift me out of the seat pushing it in. I'm not a real big guy (160lb) but what really worried me on that is that if my wife drives it (she does occasionally on the roadtrips) and she runs a tank, she won't be able to put the clutch in at all--she'll just have to drag it down against the engine till it stalls on the ramp. Just to put some numbers to it, my '03 has over 27k on it now... and I've had it 12.5 months. About half of that has been towing, but only about a 6-7k pound trailer.


My fear is that a friend has had a stiff clutch be a sign of a failing clutch/flywheel, but his was out of warranty--I don't want a known problem that showed up under warranty, screwing me out of $2k+ when it fully blows up.


Also, the dealer tried pulling some shady crap about a warped front brake rotor--GM Customer Care says 3/36 on the rotors (pads are a wear item) and the dealer tried to tell me that the brakes are 2/24. They've got a service request number, an extension at GM Customer Care, etc., and they're saying "well, we can cover it once, but after that..." Apparently, I should find a different dealership in the northern-Denver area. :(


Edit: Just as an FYI, my truck is a 2WD cab/chassis, box stock. Closest it's got to modifications are a flatbed, a toolbox, and a better hitch--we'll see what the dealer says about my tendencies to "abuse" it in 100% stock form.Edited by: ScottRS
 

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First vote of no confidence... :(


The dealer has had the truck just under four hours, and can't duplicate the clutch pedal stiffening up or the brake pulsation.


I told them that they'd have to drive it 15-20 miles at 75mph (posted speed limit here) to get it to start stiffening, and "oh, there's no way we'll be able to drive it that far".


Anybody have a regional service rep's phone number for the Denver area? A truck that's unsafe for my wife to drive, is an unacceptable state of "normal" to me.
 
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