Is there anything I can do to drop my rpm's at highway speed?? I'm running at 3500 at 55-60mph. It's even worse when I hit the 4lane. I would like to swap in a auto trans with OD from a newer truck but I don't know what kind of trans to look for. Would this be worth looking into or would I be wasting my time and money?

 

Boss50,

I feel your pain. I'm running a C6 behind a 460 with 4.10 gears. 60mph is almost 3000rpms (sluuuurp!).

I bought and am going to install a US Gear overdrive unit (they call it thier "Dual Range auxiliary transmission"). It bolts to the back-end of the C6 and provides an overdrive (or underdrive if you order it as such) of .8:1. The cool thing is that these things are beeeeeefy, and will hold up to 35,000# GCVW! It's switchable from normal to overdrive with a button you mount on the shifter **** (go to their site for more info: www.usgear.com). The shifting is manual, and the unit can be left in overdrive for when you're driving around unloaded.

You could also go with the Gear Vendors unit, which is fully automatic, but has drawbacks with expense and use (it's not rated as high of GCVW, has many more parts to make it go, and they do not recommend decelerating in OD with any sort of a load).

The E4OD is another option, but you'll need an after-market transmission controller (they are out there, but I don't remember the brand).


You could also do a combo of one of the first two with the third for ultra-overdrive!


Anyways, the complete kit for my truck was a shade over $2000, but was very complete, and very nice. I felt I got my money's worth. No extra parts needed for the install except for 2 quarts of gear oil.

No matter what you do, you'll need to have the driveshaft shortened, and if you have a 4x4 you may need to dent the fuel tank to get things to fit together, as the transmission/transfer case combo will be lengthened by about 11.5" (US gear unit) to accomodate the OD unit, or E4OD. Any driveline shop should be able to do that for you though.

I'll be putting together a tech article of my install with pics and whatnot as soon as the weather gets a bit warmer and drier for me to do the installation.

Hope that helps a bit, or at least gives you some ideas.

 

quick question about the c-6 does it have a govenor for shifting or to limit my speed?

and why is there a hose connected that when its gets loose i can only go to first gear?


thanks

 

There is a governor that tells the transmission when to shift out of 1st and 2nd...I believe on the C6 it's a deal with weights and springs that spins off of the output shaft via a gear. This can be adjusted by a technician at a transmission shop by removig int from the transmission and changing the springs to allow for more RPM before the wieghts fly out and cause an upshift (I've done this on a GM 700R4 before to move the shift RPM up on my IROC-Z).

The tube is for your vacuum kick-down...when vacuum drops (like when you floor it on the freeway) it knows when to downshift into 2nd to pass or accelerate hard. Without it connected, it thinks it needs to hold in a lower gear (1st) because it thinks you've floored it. Best to leave that connected!

 

i find it best to keep away from the 4.10 type gears. I have a c6 and 3.50 gears but 31s that take a little away and i turn 2350-2400 at 55. I personally see no benefit from the super low gears. Sure you can pull more, accelerate harder but you use more gas and wear out the engine faster.

 

I'm going to have to agree with Matt, the 4.10s are deffinately going to result in poor mileage at highway speeds. BTW, where ya at in Iowa? I just bought my pick-up, and it would be cool to know somebody in the area with knowledge of the beast.

 

small world, i'm an iowan as well, marshalltown here. cant help with the c6 tho, sorry

 

The weird thing is is that I don't have low gears like 4.10's. I have 2.75's. You'd think these would be good on the highway. I'm just frusterated from high rpms and bad mileage. I bought this truck as a daily driver instead of my Mustang but everything about my stang is better, even the mileage and acceleration.

 

What size tires do you have?

According to my calculations, at 1:1 (3rd gear) with 32" tires, you should be running about 1800rpm at 60mph.

At 3500 RPM you would be going 121mph!!!

Are you sure it's shifting into 3rd?

 

I have 31's. I'm pretty sure it's shifting into 3rd. I've counted the shifts before, unless my tach is that far off.

 

6 or 8 cyl? It's possible the tach is not set correctly for the engine in your truck.

For example, if you have a 6 cyl, but the tach is in V8 mode (I believe there is a selector wire that needs to be grounded for the 6s) then it could be showing 20% more RPMs than you are actually turning.

Just a thought...

 

the reason why i asked is that someone suggested me to remove the pvc system for some reason i dont remember, probalby because of new air cleaner, anyways from the pvc it goes into the wiper area where it has 3 hoses one going into trans ant the others i dont remember. so im stuck

thanks

 

I live in Onslow about 200 people its 45 miles northeast of cedar rapids. There a are few members around the urbandale area I believe.


And boss 50 if you are turning 3500 you don't have 2.75 gears anymore. They have been swapped to like 4.56 or you are in second gear. But if your c6 shifts twice you are in 3rd gear and if you are turning 3500 rpm you can tell by the sound of the engine if the tach isn't working. And yes make sure the cylinder selector on the tach is at 8 because at 6 and 4 would would be turning crazy rpm. I have left the 4 setting on my 300 6 and it turned liked 8000 rpm if i remember correctly while on the right setting it could only go to 5500 max.

 

Herman,

I am not sure that he was right about the vac line to the tranny. Mabey someone else can confirm this for me as well.

Isnt the vac tube that runs to the tranny what makes it shift up and down under normal acceleration??? I was under the impression that the kickdown into passing gear was accomplished by the kickdown linkage ( metal rod that connects from the linkage on the drivers side of the carb to the shift linkage on the drivers side of the tranny.)

Anyway, I dont think that you are stuck.. I assume when you say that your buddy told you to get rid of the pvc stuff he meant to get rid of all the emissions crap. you can still do this (If your state emissions laws allow) I did it on my plow truck- 83 f250 460 with a c6.. also on my 80 150 with a 302 and a c6.. I have the vac line from the back of the carb run directly to the tube on the tranny and do not even use the 3 leg tee that is mounted to the firewall..

I hope that this helps.. and if I am wrong will someone please correct me.


also, does anyone have the kickdown linkage (the funky-twisty bar) for a 302 with a C-6 and a 2bbl carb. I have been looking for one for 3 years and cant find one.. the only thing that I can find is one for a van and it will not work.

 

UglyTruck,

You may be right...I know that some vehicles use a kickdown lever off the throttle, and some use a vacuum-activated kickdown device. Depends on the vehicle I think....but they both accomplish the same thing.