6 speed transmission

smokey · December 11, 2001

Does anyone know if there is a difference between the ford and chev 6 spd manual transmission for the diesel engine? I know they are manufactured by the same company.

Thanks.

Kansas Kid · December 11, 2001

Supposedly there were some changes that GM requested be done for their version of the transmission to make it easier to shift and transmit less vibration through the shifter. If they actually did, I don't know because I don't have enough experience with the GM version to compare. I do know that GM uses a dual mass flywheel as opposed to a single mass flywheel used on the Fords. The dual mass tends to have some problems as power levels are increased, but it does damper alot of vibrations from the engine going through the drivetrain. I also know that the clutch release on the GM trucks is absolutely pathetic...

smokey · December 11, 2001

dang I am trying to find a reason to trade my Ford in for a Chevy Dmaxx but most things seem to point to getting another ford.

Those clutches in the powerstroke are hard to push down as compared to the ones in the gasssers. Get good exercise driving them.

Kansas Kid · December 12, 2001

The one comment I have heard about the GM clutch is that it is the easiest of the big 3 to push in, it requires alot less effort. What I noticed in the one I test drove (I've heard several people complain about this), is that the clutch seemed to be either fully depressed or fully released. It was like I had never driven a manual before, because you could not get a smooth start. I heard that by simply removing a spring from behind the clutch pedal fixes this, but I don't know. ???

But the worst part about them is trying to even find one. Gm allocates 25 Duramax engines per day to go in front of the ZF out of the 400+ per day they produce...

Larry · December 12, 2001

I have a 01’ extended cab shorty 4x4 with an 8.1 and ZF S6-650 with 4000 miles. I was one of the guys that posted on other threads that driving this truck was like I had never driven a manual before. While helping out around my dad’s shop I learned to drive a stick when I was barely old enough to reach the pedals. Every 4x4 truck I have ever owned has been a stick except for a couple of two-wheel drive hotrod trucks that I currently have cluttering up my garage. It seems the pressure plate on this 01’ HD likes to be either fully engaged or fully disengaged with little or no slippage. It is almost impossible to launch it smoothly without jerking it to death, pealing off a couple 32nds from the tires or killing it. I have looked into the clutch pedal spring folklore tale with friends in the truck TAC group, which has turned out to be a false rumor. It seems the condition is with the pressure plate but no repair is necessary, as the condition is considered normal. Despite all the hype around the ZF, I think it has the most awkward shifting manual transmission on the market not to mention the shift gates are still as notchy as Fords. I would have much rather seen GM use the NV5600 6 speed as the Dodge Ram uses instead of the ZF. The ironic thing is GM had originally planned on using the NV5600 in the HD’s but was nixed it close to the media launch time.

Normal or not I am starting to wish I had adopted for the Allison instead. The only reason I bought this truck over the one I really wanted to order was because it was the right color and already in the dealers stock when the 0% interest rate was introduced. My dealer also had identical trucks as mine with Ally’s but they had the NP1 electronic shift transfercase. No way in hell was I going to settle for the NP1 option as a career detour through Detroit has burnt a negative image of electronic transfercases in my mind forever.

quadrunner500 · December 13, 2001

No complaints from me on the ZF 6 spd or the clutch. Still lovin' it! (Maybe I'm just a better driver?) ;)

CMNTMXR81 · December 13, 2001

Guys, guys, guys....it has to do with the hydraulics (master cylinder and slave) that actuate the slave and throw out bearing that make it easier to work than older trucks. Not the flywheel or clutch itself.

If this clutch and hydraulic setup is similar to the ones used on LS1 powered F-body's, be prepared to do some upgrading if you plan on upping power levels.

GM changed them from a push style (to release pressure on the pressure plate) to a pull style and it isn't as effective in holding power. Unfortunately, GM or should I say Valeo the maker of the clutch, has patented this system so no one on the aftermarket can sell one without paying royalties.

To those being diswayed on whether or not to purchase a Chevy or stick with ford, it's not the trans itself, just the clutch that needs attention.

Kansas Kid · December 13, 2001

Well, I did something stupid and forgot to mention that there is a major difference between the GM and Ford version. Ford learned this through experience, yet GM decided not to use it anyways. The Ford version comes with an external oil cooler, similar to what is used on the auto transmissions. GM decided to get rid of the cooler and use synthetic fluids to combate the higher temperatures.

Now you may think that a manual transmission doesn't need an oil cooler, but they do, especially when you tow alot in OD. Ford found that out with the first year they installed the ZF S6-650 without a cooler. Wonder how long it will take GM to figure this out?

btw, I wouldn't wait until going up in power to change the clutch on the Duramax/ZF I drove. If GM wouldn't fix it, I would have to do it before long, because it was awful. Must just be the luck of the draw since Quadrunner doesn't have a similar problem with his. I still like the ZF better then the NV5600 in the Dodges though.

Timberline · December 21, 2001

I too have the ZF6 and when I first drove it off of the dealership lot I also looked like I had never driven a stick before. Yes, I was embarrassed but when I came back to the dealership to sign the papers I let the owner of the dealership drive it and yes he looked like a beginner too. It doesn't take long to get the hang of it and before you know it you are shifting it smoother than any automatic ever could.

I'm glad I ordered the 6spd. No complaints here.

CMNT81 · December 21, 2001

Kansas, unfortunately there isn't an aftermarket clutch available that is compatible with GM's new "pull" style hydraulic slave system. There are clutches available, but generally you either have to convert to their hydraulic system and/or shim the clutch and continue to re-shim as it wears in.

GM's supplier, Valeo patented the "pull" style slave, so no one on the aftermarket can copy it's design without paying royalties.

It sucks cause I've gone through three clutches on my Camaro because of this stupid design.

Kansas Kid · December 22, 2001

Geez CMNT81, you just know how to make a guys day. LOL That royally sucks about not being able to get a direct fit aftermarket clutch. I guess its a good thing for GM's supplier, but not for anyone who has to drive a vehicle with this setup. Then again maybe us truck drivers are extremely lucky, and GM didn't use the same setup as your Camaro. ;) I can't say I know much about the setup as a whole they are using, other then it has a dual mass flywheel.

But whatever happens, when I get a Duramax/ZF trucks, it is going to go up in power. You can be sure of that, I just hope by then somebody has a clutch that can hold it all...

CMNT81 · December 22, 2001

Oh trust me, if I could tell you my tales of woe in regards to my clutch.

GM has gone with this new style "pull" hydraulic system in all it's higher power applications. Why? I dunno.

Dual mass flywheels only will exaberate the problem as their is more the clutch has to fight against to hold.

A lot can be overcome by changing the pressure plates springs to increase it's clamping force, but you run the risk of overpowering the hydraulic system (primarily the slave and it's throwout bearing), in which case when you pushed the clutch pedal in, noting happens....anotherwards, no disengagement.

Quite frustrating indeed.

quadrunner500 · January 10, 2002

Hey K-Kid,

I wuz lookin' under my truck briefly, and noted some kind of a cooler (heat exchanger) right next to the fuel tank. I didn't have time to see where the lines went, but maybe there is a transmission cooler on the ZF 6-spd?

Tom

Kansas Kid · January 10, 2002

I'm going to make an assumption that the cooler you saw was directly in front of the fuel tank? If so, that is a fuel cooler. The fuel gets heated pretty by the time it is returned to the tank, so it has its own cooler. I will try to find a picture of this if I can.

The ZF tranny cooler on the Fords goes up front towards the radiator just like an auto transmission cooler.

quadrunner500 · January 10, 2002

Okay. That's what it was then. You're right, just in front of fuel tank. A fuel cooler occurred to me, but I thought how could it get hot just being in the tank? (forgetting that it's circulating, and being returned to the tank.)

You the man! Thanks,

Tom