Well, I finally converted my truck over to a ZF6 manual trans and manual Transfer case. Took about 20 hrs, but was well worth it. I have not driven too many 6 speed 7.3's so I had a few operational questions about it. It seems to shift well through all the speeds, but in third gear under power, the shifter bounces around quite a bit compared to the other gears. Get off the accelerator and it stops bouncing. I am thinking something may be bad internally; but what? Next I noticed I can't get into 4x4 high if I am driving, all I get is grinding. If I stop it goes in just fine. Is the manual transfer case not capable of 'on the fly' changes? Finally, If I am decelerating and put the clutch in to come to a stop, the engine speed drops at a predictable rate, but it keeps going down to around 400 rpms then returns to curb idle. It only does this sometimes but not in neutral. Have any of you 6 speed drivers noticed anything like this?

I appeciate any comments!

 

Welcome to the zf6 club.

The 3rd gear issue sounds like it could be something wrong but as long as its not going to pop out of gear I wouldnt be worried.

The idle drop issue is normal, some trucks do it some trucks dont, some truck do it bad some truck do it a little.

I can look in my owners manual but I am pretty sure the manual T-case is not suppose to be sift on the fly.

Anything els let us know hope i was some help

 

Yeah, it seemed like it was draggin down to below curb idle then comes back up. Sometimes the engine knocks once as it comes down. I will try to get a video clip of the 3rd gear shaking deal. Oh, one more thing. I noticed where the transmission case comes together there was some sort of red grease coming out of the casing seperations and was not sure if they even used sealant on the casing faces or what. It was definately not transmission fluid, and it isn't leaking either, but I am curious on what is was. Assembly lube? Seems strange at 98,000 miles for it to be seeping still. The ZF6 sure is much stiffer to shift than the ZF5 7.3 I drove for years, but then again, this tranny has less than half the miles. Thanks for the help!

 

The manual t-case is only shift on the fly if you've got the front hubs locked in. I've popped it in 4wd at 60mph without a hint of grinding. Also, don't shift the t-case into neutral with the engine going. Trying to get it back in gear without grinding doesn't work...at least on the auto.

As for the drop at idle, my auto will do it if I coast downhill for a long time. Once the t/c unlocks and the rpm's drop, its like it takes a second for the injectors to kick back in and keep it at idle. Sounds like its gonna stall out on occasion.

 

Don't know about the 3rd gear issue. My truck drops to the same RPM when I press the clutch in. Also the manual t-case should be able to shift on the FLY

 

Did you change the PCM? The PCM gets info back from the transmission that affects how it runs. A chipped PCM that is programmed for auto will almost not run in a 6 speed (at least it runs very poorly). This may be the reason for your idle problem.

 

I believe the manual states that you can shift into 4-hi up to 55 mph. As long as the hubs are locked & the front wheels are turning the same speed as the rears, you shouldn't have any grinding at all. Now if you were sitting still & spinning the rear wheels & shifted it, you would have some grinding. I have an auto but my manual t-case is smooth as silk going into 4-hi. You have to come to a stop for 4-lo.

 

Welcome to the club lol.
As mentioned some trucks the shifter will shake a good bit, some don't mine does, it just seems to hit a sweet spot with the vibration and rotating parts and will shake a little, alot like an out of balance tire that only does it between 55-60mph.
I have the same rpm drop, its typical when the engine goes from a load, to zero load quickly like when you disengage the clutch. Its normal.

The PCM should have nothing to do with it, you can run an auto PCM in a manual trans truck, and everything will perform spot on other that the CEL will stay on. You can also run a manual PCM in an auto truck, the motor will run fine, but you will have to manually shift the gears on the column.

x2

 

Jody told me the tunes for manual are very different from auto - something about torque curves being different. I've never noticed the idle drop you described, but my truck hasn't been 'stock' for a looooong time... (315k miles total)

The little button on top of my shifter where the #'s are has been loose a long time. It has just enough play to 'buzz' at highway speeds. I generally put a piece of tape over it to shut it up. Never had any bouncing in any gear. I don't think I'd pull trans unless it was jumping out or develops trouble going in or out of gear.

What clutch did you use? Did you use stock-type pilot bearing??

 

The RPM issue is not an issue they all do it. The only red grease commonly used that i know of is Dielectric I dont know why that would be there???

 

Thanks for all the replies! Yeah, I feel like an idiot. I had the hubs disengaged and was trying to use 4 high. I locked the hubs and it all works great now. haha. I noticed I may need to pcm reburned sometime as on slight inclines I have to really feather the clutch to get going or use low, so maybe the torque output is lower or something with the auto. I could be crazy though. I also noticed since I have a bare metal floor that the hump gets really hot even though I have the radiator cooler still working but once it gets airflow around it, it is only warm. As far as the clutch, I got a south bend with a kevlar bushing. It sure works nicely!

 

Got any pics? How much did you have to modify the hump?

The auto is detuned, but I didn't think it would make that big a difference starting off. I never have to feather my clutch. Get the chip and you'll be happy.

 

Are you starting off in "1"??? Im running a SB clutch and can use the clutch without any throttle on small inclines to get going.

 

I have 108 pictures which I plan on doing another 'how to' since a few people had asked for it. I start out in 1 but have to bring up the engine speed quite a bit to get going. Low I can get going well. Just seems like I have to hang onto the clutch longer than the IDI 7.3 we had. I can pretty easily stall it in '1' if I bring out the pedal too fast. I hopefully will get the how to posted in a few weeks. The floor pan had to be trimmed a lot.

 

Without a heavy trailer attached, I'd have to leave my foot on the brake while letting the clutch out to get mine to stall. Get the PCM re-flashed or get a chip. A stock ZF-6 has about the same power as an auto with the Edge programmer, so you're going to need more power.