Screamin' down the highway!

[Farmall Ford]

Hey ya'll, posted a couple months back about purchasing the 87 f250 6.9 w/c6 tranny. The tranny was supposedly "built" as it was used mostly for pullin horse trailers. I let it sit for a while and finally got it running pretty strong. Decided to drive it to school today, noticed when I was around 45mph the tach read about 22-2300rpms, 55 was about 26-2800 and 60 was pushin 3 grand. Im guessin there must be some pretty big gears in this thing? 4.10's or 4.56's? Any ideas? Thanks

 

[Greg5OH]

410s and non locking converter!

 

[Farmall Ford]

Ughh not what I want to hear lol...not another faulty part. If it is my torque converter not locking could that be a simple fix or should I go ahead and order a new beefed up converter?

 

[OLDBULL8]

It's not a faulty part. C6 trannies don't have a lockup convertor. RPM's your seeing is normal for that tyranny. Only thing to fix that is a over/under drive or different rear end.

 

[79jasper]

C6's don't have a locking converter.....

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[Farmall Ford]

Ok thanks guys lol haven't done any searching on the "issue" yet

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[vegas39]

410s and non locking converter!

I just did a c6 conversion from 5 speed on my truck with 410's and added a Gear vendors to compensate for that very problem. It is a sucky setup if you dont have the overdrive unit.

 

[1466IH]

How big of a deal is it to switch to the e4od a truck that i am looking at has a c6 and those speeds would never work for me lol

 

[icanfixall]

A complete wiring harness is needed for a E4OD trans swapped inplace of a C6. Or an aftermarket trans brain like Bauman or some of the others. But its plenty of work doing that swap. A Gear Vendors is a much simpler addition to get the rpm's down.

 

[1466IH]

I may be easier to go with a GV but my labor doesnt cost me a dime but if it is that big of a deal i would just go to a zf. i didnt know how much different they were if it was all internal or what

 

[Coyote_Red]

I think you have even higher than 4.10's more like 4.56's. 4.56's puts your RPMs at 2296 for 45 MPH.

 

[Farmall Ford]

Those are about exactly the rpms I'm running...time for a gear swap or are these good?

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[Coyote_Red]

That depends what are you are trying to do with the truck?

 

[Farmall Ford]

Pull trailers..daily driving..possibly a local truck pull for fun

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[Coyote_Red]

I would say that 3.73's would be a good all around gear set, for more economy you can put in 3.55's.