(It takes about a second to shift into Overdrive and I think you have to get off the gas a little. On a 0-60 run in 6 seconds, where is the time to shift the overdrive box?)

Wrong! I have a GV behind a 511 stroker. The shift to OD is instant and you do not need to get off the gas a little, keep it to the floor.

(BTW, the internal workings of the GV look very similar to innards of a TorqueFlite, a planetary gear system with a multidisc clutch. The pressure for the clutch is provided by a pump in the casing.)

Yes it is a planetary gear. The clutch isn't multi-disc, it's a cone clutch. Correct the GV has its own internal pump and sump. It's a single piston pump, about 3/8 di.a.

I'm not trying to be a smart a$$, but have you ever driven a car or truck with a GV installed? Have you ever actually opened one up and looked inside?

As far as the split shift goes it's not practical. Since I have a manual reverse valve body I drive mine like a four speed. 1, 2, 3, OD. If I'm getting on it hard, it's 1, 2, OD, 3. I disabled the GV auto feature and manually select OD. The only draw back to disabling the GV auto feature is you have to remember to deselect OD every time you stop.

"This is the point where we end the gear splitting discussion. It's not needed in a torquey engine with a broad rpm range."

Wow... Pretty arrogant to pop into a thread and try to steer it the way that you want.

My week long experience with a Gear Vendors on a 727 with a stockish 440 was that it was not enough overdrive to warrant the expense and the gear splitting was slower than leaving it alone and shifting it into the overdrive in 3rd.

'Refreshing' to see this mentioned. Most peeps usually 'talk it away' by just saying they're happy with it after having spent about $3k?

Interesting..

My 67 Coronet has 294 gears in it ( automatic) as I like to drive it places.. They are getting boring though...

My research shows a 355 geared car with the GV unit would have an OD comparable to 274 final gears???

Seems pretty perfect to me??? What am I missing??

My 69 Bee 3.55 gear + GV = 2500rpm @ 80mph. My engine is happy, I'm happy. Was it worth $2600? Yep every penny!

New development to my project:

As rear ends go, I have had a few recommendations to NOT do a Dana 60 due to the additional weight. Some guys that race Mopars at the track are actually recommending that I go with a Ford 9 inch. Have many of you heard of this swap? What are your thoughts? I'm making the final choice in a day or two.

Car Craft did a test, used the Dana 60, the 9" and the 12 bolt.

http://www.hotrod.com/how-to/transmission-drivetrain/ccrp-0806-chevy-chevelle-rear-axle-swap/

Some facts for you rather than anecdotal bench racers opinions.

Sheesh . . . if you are thinking Ford 9 inch, then why not go with Mopar 8.75 ??? There were many made for your car . . . just an FYI . . . as was mentioned before, depends what you want to do with your car. I have a 74 Duster360, original 360, 727 auto. It had original 8.25 rear end with 2.94 gears, thought I would like more, so got 3.55 sure grip installed. However, I like driving long distances . . . so these really didn't seem like what I wanted . . . before going to Carlisle, PA show in 1999 I swapped out complete rear for another 8.25 with 2.45:1 gears ! Much happier !!! The 360 still cranks over the right tire (yes one legger) no problem, travelling down the road at 75mph, engine ticking over at 2600rpm, and mileage around 22/23 mpg all day long ! . . . Just my two cents worth . . . build the car YOU want ! . . .

Cheers

Mark

That is a lot less weight difference than I thought it would be.

Wonder if disc brakes would drop the weight more.

Late to the party, looks like a lot of info to pour through in this thread.... but just want to offer that the mere thought of putting any money into an 8-1/4" is silly. And no, it won't stand up to ANY sort of real torque. Whatever website you saw that said it would stand up to 500 hp.... Don't go there anymore.

What rear gear were you running and what tire height?
I'm at 2650 RPM's at 60 MPH on the highway in my Duster with 3.55's and a 27" tire, I know darn well an overdrive button would make me much happier at around 2100 RPM's.

Probably because the 9" is about 10 times stronger. There are alot of fast cars with 8.75 rearends but alot of them break too.

Not stock they aren't.

This is a good point. A 9" is a good rear end, but mostly because the aftermarket has offered them a lot of support. In stock form, they are a far cry from a Dana60, which can handle just about anything in bone stock form.

I was just reading this for fun and have no overdrive info to add but I feel I need to plead with you to NOT put a Ford 9" in your Mopar! You have an 8-3/4, 9-1/4, and Dana 60 to choose from so there is no reason in the world to put another brand of rear end under your car. Please don't be that guy!!!

I also have a 67 Coronet with 3.55 gears and a gear vendors unit. I have three cars with gear vendors units and I very happy with them. Found all three on craigslist and bought for less than half of new price.

Also have to add what others have said. I use it as an overdrive only because of the slight delay.

Stay calm everyone, I'm pretty sure I'll be doing the Dana 60

Hey rapom, when you picked up the gear vendors used did you have to change anything on them? They seem to be tuned for gear ratio and tire size.

Any over drive trans will produce about the same effect as the Gear Venders unit at a much lower price. The only advantage the GV unit has is it can handle more power. The 727 version of the Mopar overdrive automatic can be as stout as your current 727 or most of the Mopar OD 4, 5 or 6 speeds will work at probably 1/2 the cost of the GV unit, even after converting them to fit your big block.

My 93 Dakota 4x4 pickup has a Magnum V6, 500 auto od, 3:55 8 1/4 rear and 235-75-15 tires. It will roll down the road with the od off (switch on the dash) at about 2600 at 60 mph. Turn the od on, and the rpm drops to about 2100, and when the converter locks up, the rpm drops to about 1800 at 60 mph. The V 6 doesn't have enough balls to pull a long hill at a steady 60 (it does better at 70) without unlocking the lockup converter, and if its a really long hill, it might drop out of od. Out of od, I can gain speed going up nearly any hill. A V8 would probably pull the hills without issues. On the highway, my 4x4 Dakota gets around 20 mpg at 70 mph. Gene