in debating to swap a C6 for my sloppy 5 speed, what kind of rpm do you run on the highway, say around 65. my truck has the weeny 3.08 if that helps, and 31 inch tires...

 

I would guess the same as your trans in 4th.

 

It's a little higher than your manual in 4th, the C6 doesn't have a lockup converter so it's going at a little higher RPM's. My C6 in my bronco ran at 3100 RPM's at about 63 MPH. This is with 3.55 gears and stock tires. I'll post back in a minute with what RPM it should be at.

Matt

 

Ok, with 3.08 gears traveling at 60MPH and 31" tires your truck should be running at around 2100 RPM's.

 

that doesnt seem too bad, i bet it would be a pig from a standing start though, i'm not sure how the c6 gears are spread out...

 

The c6 uses 2.46, 1.46, and 1:1. It won't be as slow taking off as you'd think because of the torque converter. The converter is multiplying the tq output of the engine so it helps you get going faster. Like in drag racing, most automatic cars/trucks will 60' quicker than than the same vehicle with a manual. But, the manual will usually mph better cuz they are locked up and no loss through the converter.

 

gotcha, good info, a lock up converter was mentioned earlier, is there such a thing for the c6?

 

No, not as I know of. I think the AOD was the first one to come out with it, If your doing alot of highway use that would be the one I'd put in a truck. what are you putting that tranny behind? If you have one built they can handle some power. If it's a 300 or a 302 you can probably keep it stock with maybe a shift kit, but with a 351 you might want to consider having it built.

Matt

 

I recently swapped my AOD for a S.B. C6.
The Aod is an O.D. Trans but it is really weakly built from the factory specs.
They have a nasty problem with the Throttle Valve having to be set correctly or they will burn up even quicker.
You can build them up by switching parts with various other transmissions.
But the cost is really expensive compaired to just having a factory C6 that is well built from the factory (not to mention adding other upgrades like wider intermediate bands and R-Servos, Ect to the C6 relitivly cheap)

The swap for me was beautiful , the mounts all lined up , the shifter still reads O.D. but it is a 3 speed still.
The only major problem I had was cutting the Drive Shaft back a meer 3 inches. the smallest C6 tail shaft is suppose to be 13.5" as I have, it was still 3" overall longer then the AOD.

The C6 is a perfect beginner Transmission to rebuild also, I tore mine down and rebuilt it in 2 leasurly days. All the "Guts" are big (Tonka) in it compared to the AOD. It's shift points are adjustable with a small screwdriver in the back of the accumulater valve, and the intermediate band is adjustable from the out side (10 Lbs with a torque wrench, back it off 1.1/4 turns or so , and tighten the locknut.

C6 rebuild kit (soft parts ) $90
AOD rebuild kit (soft parts) $120 and much more complicated , smaller parts and much less forgiving tolerances.

New torque converter for the AOD was $130 (low stall)
The C6 was $70 for various stall speeds

I am much happier with the swap, regardless of loosing the O.D. gear.

Now I want a beefier rear axle with a 5 lug set up, I still have the little (8.8 3.55 factory ......I think) factory axle. But I'm sure it wont last long once the 40"s are on.

 

Noneshere, great info. I was saying if your going to use your truck for a daily driver, and not just for racing or towing a C6 has some strains, but I guess with a 3.08 it isn't really that bad.

A C6 stock can handle a 460 or a 429...back in the old days some of these motors made about 500ft lbs of torque, so you'd have to build one heck of a smallblock to tear it up.

Matt

 

I have a C6 behind my 351 and I am very happy with it. Like Noneshere says, the C6 is both durable and simple. My truck has 133,000 miles on it and before I got the truck a year ago, my grandfather put better than half those miles on the truck towing an 8,500 pound trailer. The only work that has been done on the transmission is fluid changes, intermediate band adjustments, and 1 new vacuum modulator.

 

I have the C-6 as well. I have always liked this one as it is almost bullet proof. Behind the 351, it works great and has no problem starting out. I usually find myself going faster then I want to when I start from a light so I have to watch it. I have an L/S 3:55 with almost stock tires.

As a side note, I sold my '67 T-bird about 2 years ago with a 428 4bbl. It had the C-6 in it as well and I never had a problem with it.