Gear Vedors Oveerdrive

[hemirr]

Anyone have any experience with a gear vendors overdrive behind a 727 with a big block?  I have a 68 Charger with a 440 and 3:55 rear.  At 60 mph I am turning about 3200 rpm.  Way too much for me.  I am thinking about the gear vendors unit.  Expensive but supposed to be bullet proof and worth it.

[mauve66]

some love it , some hate it, some of us have yet to try the one installed in our car

[Rolling_Thunder]

something is wrong there ?   With a 26" tall tire and 3200rpm you have 3.91 gears...    not 3.55s

[Musicman]

something is wrong there ?   With a 26" tall tire and 3200rpm you have 3.91 gears...    not 3.55s

Nothing wrong there... The torque converter is always subject to a certain degree of loss, and 15% is about average

http://vexer.com/68rt/speed.html

As far as the GV unit is concerned... go for it if you have the extra cash. Just don't waste time trying to use it as a 6-speed auto like some folks do. Yes, in theory, with enough practice you might actually get good at it, but the bottom line is... Who has time to waste shifting and pressing buttons 999 times when your running the 1/4... and who needs 6 speeds on the highway? Just use it for the extra gear and be happy. As far as their strength is concerned... Bullet Proof is a pretty good description.

[Mike DC]

   
IMHO the Keisler conversion (puts in a modern GM 4L60E electronic tranny that's a bit beefed up, and goes in with no cutting the car) seems like a better setup on paper.  A legit 4-speed tranny, a lockup torque converter, ideal gear ratio spread, total control over the shifting characteristics, etc. 



But it's expensive as a MoFo, like $4K I've heard. 

And some guys in the hobby have not liked dealing with Keisler as a company. 


-----------------------------------------------


As for Gear Vendors,


The bad news is that the "gear splitting" stuff isn't realistic, like Rolling Thunder said.  Consider it an electric 4th gear, nothing more.  And the extra gear is only 22% overdriven, which is a pretty small reduction for all that money & effort IMHO no matter what Gear Vendors says about it.

The good news is that it's said to be strong as PHUCK.  I think the unit itself is rooted in an industrial trucking item and it's really way overkill for passenger car purposes. 

 

The GV is really more like an electric switch to change the differential ratio than anything else.  With the until behind the rest of the tranny, if you leave it engaged then you've basically just raised all 3 of the stock 727 ratios. 

 

[Musicman]

The GV unit has 2 modes (Manual & Automatic)... In Auto mode, when bolted to a 727 TF it acts just like any normal factory overdrive, kicking in at the upper end of the scale only. It has no effect on the first 3 drive ratios, they remain the same.

In Manual mode you have the ability to apply the overdrive to all 3 speeds. This is where the 6-Speed hype comes from... This feature might be kinda cool to play with on a weekend cruise, but I personally don't see it as a practical application for the track.

Myself, I like the GV unit, and I will be using one behind my new engine build, in the form of an SMR Pro Sportsman Shortie. I'm primarily using the unit to boost my fuel economy on the Highway however... but of course, having an extra gear at the track doesn't hurt either.

[68n70]

I have virtually the same setup as you ('68/727/3:55 gear even!) and I have a GV unit and love the unit.  I'm looking for a 4:10 or thereabouts though as w/ that gear and the GV, I'm shoving people down the road now!  (If you want a good highway setup, put one in there and GO! The GV turns a 3:55 into something like a 2:72!)  Me, I want a little more off the line torque so I'm opting to give up a bit of topend for more down low.  I figure w/ the GV I can still be happy on the highway with more low end gear. 
If you have the coin, I'd say go for it I think you'll like it!

[Ghoste]

Do many people actually use these things in a drag racing situation?

[68n70]

The guy I bought mine from did use it when he raced.  How much it helped or not, I couldn't tell you...nor, do I think, could he!  I think if you set everything up to maximize 4 gears, it might knock off some time.  However, I think first and foremost it's simply a true overdrive.

[Ghoste]

As much as a hindrance or help I think I was just as curious as to their durability under those conditions. 

[Mike DC]

 
I've never personally heard of anyone breaking a GV unit in a car under any conditions, period. 

   

[Ghoste]

I hadn't either but I also haven't really heard of them being used under extreme conditions.   Other than the guy 68n70 bought his from I've only heard of them being used for highway cruising.

[mauve66]

supposed to be good to 1200 HP

[Troy]

I'd think that you wouldn't actually use the GV while racing but it would certainly be handy for the trip home. I remember Chryco talking about using the OD 4-speeds and just using 3 gears at the track - partially because 4th is the weak link on those but also because 3 gears seems to be plenty for hitting max RPM when crossing the line. What RPM would the engine be turning at 100-120 MPH with the GV on? Even with 4.10s I don't think it would be very high. Assuming a street car of course.

Troy

[NYCMille]

I have the GV unit in the Charger and the Keisler in the Daytona.

GV
Pros: Bullet proof - I've road raced, autocrossed, drag raced and generally just abuse the ever-lovin'-crap out of it and have never had one issue in 38 thousand miles.
Con: As mentioned, it's only a 22% drop. I run a 727/w 3:55s and a 27" tall tire and 80mph is 3000 rpm, which in all honesty is not too bad considering.

Keisler:
Pros: It's a real overdrive - at 3000 rpm running same combo as the Charger I run at 106 mph... that's a BIG difference.
Cons: It's notchy as hell with long throws - this doesn't mean it's not fun, it's just the GV unit behind a reverse manual valve body is MORE fun 

[Rolling_Thunder]

agreed - the Tremec TKO is indeed a notchy b!tch...     but it is still a nice trans...     34% reduction in rpms ---   a lot better than the 22% like Mike stated...    I am actually running the same set up as Mike