Gear Vendors overdrive for 1969 Coronet R/T

[1969CoronetR/T]

I have a 1969 Coronet R/T with a 500 (440 stroked to 500) cid engine with ported Indy EZ-1 heads among other engine upgrades that was just built last winter. IT has a A727 automatic and a 3,000 stall converter and 3.55 rear end gears. I was looking into a Gear Vendors overdrive unit as my car is in the 4,000 - 5,000 RPM range on the highway doing 55 MPH. I am worried about the abuse the engine is taking while cruising down the highway, but I love the acceleration from red light to red light. Will this unit slow the car down on the street?

 

[68GTX4SPEED]

I have 3.54 and revs 2350 at 55mph, manuell not 727, must be something wrong with your tachometer can't be between 4000-5000, here you can check different numbers in the rear, http://vexer.com/automotive-tools/speed-rpm-calculator and a GV is great stuff have one myself just go for it 4.10 x 0.78 = 3.20 the best of two worlds.

 

[Grabinov911]

If you like, follow along in these two threads to learn about my Gear Vendor install - going on as we speak:

http://www.forbbodiesonly.com/moparforum/showthread.php?101531-Help-Transmission-not-centered (this thread is about a specific install prob w my car)

http://www.forbbodiesonly.com/moparforum/showthread.php?36174-80-Grit!/page6 (about the Gear Vendor and install)

Picking up the driveshaft in the morning and hope to be driving it tomorrow with just basic 12v wiring to the solenoid for manual shifting.

Boy i couldn't find anything but the basics on the Gear Vendor a month ago. Seems to be getting some interest now...

 

[mopar 3 B]

You may want to get clarification of land speed and rpms before spending 3000 on the gear vendor. Lowering engine rpms from where it likes to run maybe of no real benefit and just create other problems like plug fouling, converter burn and pour fuel economy. 3000 will buy a lot of fuel for a non daily driver.

 

[Kern Dog]

You are low on transmission fluid if you are spinning over 4000 rpms at 55!

Seriously...Either your tach is WAAAAAAY !! off or there is some serious slippage! I have 3.55 gears and 28" rear tires. I'm spinning 2600-2800 at that speed and I have a 11" converter that stalls about 2500.

If you are looking at the Gear Vendors unit regardless, it is a quality product. It does not draw much HP and even if it did take 10HP to spin, the gas savings/increase in driving range/reduced engine wear and quieter cruising is worth it. I just wish they had a taller ratio, something closer to .70.
Forget their bragging about gear splitting. You'd need a bionic/terminator type reflexes to shift in and out of OD every gear change if you have a fast car. Gear splitting is for truck drivers.

 

[Grabinov911]

Forget their bragging about gear splitting. You'd need a bionic/terminator type reflexes to shift in and out of OD every gear change if you have a fast car. Gear splitting is for truck drivers.

:rolling: :rolling:

 

[MT_Mopar]

Something is not right, my car is a 446, fair size cam, big victor heads, TF727 and an 8-3/4 with 3:73 - I'm right at 3200rpm @ 70mph, GPS speedo.

 

[1969CoronetR/T]

I agree that my tachometer must be off. It screams going down the highway.

 

[1968rick]

Electronic ignition with a stock tach?

 

[cdr]

is it shifting into 3rd gear ?

 

[Kern Dog]

is it shifting into 3rd gear ?

:laughing4:

 

[cdr]

:laughing4:

with his gears 2nd gear would be about 3700 rpm with converter slip @55mph

 

[1969CoronetR/T]

Yes, it has two hard shifts and O have electrical (1970?) ignition with a stock tach. I took it out yesterday since it was close to 60 degrees and the tach seems to be pretty accurate. I was first at a red light and once the light turned green I jumped on the pedal to 4000 RPM and it stayed around that range for a minute or two. I looked up and everyone else was a distant memory in my rear view mirror. I would guess (I did not have my GPS app on) I was doing 50-60 miles per hour at 4000 RPM. I love the red light to red light acceleration even after I dropped the gears from 3.91 to 3.55. I take it to work on Fridays during nice weather and it is a 20 mile ride on the highway. I am worried about excessive engine wear so I was looking into this GV unit, although I would hate to change the dynamics of the street acceleration (red light to red light).

 

[KarNut46]

Have you thought about the possibility that you may have a torque converter problem? I had 3.91 gears in my 65 for a while and it didn't run those revs at 70. Torque conv people may have screwed up in the assembly or labeling at the factory.

 

[1969CoronetR/T]

The converter was custom built by the transmission shop when they beefed up my 727 last winter so I assume it is in good working condition (3000 stall). I will wait until the spring and see if the shop down the street can calibrate the RPM to make sure it is completely accurate.

 

[KarNut46]

'nother thing to check. Is the speedo pinion gear correct for your axle ratio? That's the little nylon gear that slips into the tail housing where the speedo cable hooks up. Here are some numbers that I got a few years ago out of a mag. For 3.55 gears by tire diameter: 24"=39t, 26"=36t, 28"=33t, 30"=31t. With other tire sizes you'll have to wing it (guestimate). If this gear is off by much the speedo will either read slow or fast. Whenever I can't locate a problem the first thing I replace is the least costly related item.

 

[1969CoronetR/T]

Speedometer does not work. I have had it rebuilt twice and both times it works for a month or two and eventually breaks again. Frustrating to say the least so I use a GPS app on my phone if I am out on the raod alone so that I do not get too far over the speed limit.

 

[Kern Dog]

You have serious problems with accuracy.
No speedo? You are either getting poor service or bad parts. people here have 50 year old cars with stock speedometers still working fine.
In the interest of bypassing your mechanical troubles, you can tap into the NEG coil wire with a known good tachometer and drive along a person with a newer car. Tell them to drive at 60 mph, match their speed and look at the "add-on" tach.
Factory tachometers are notoriously innacurate.
Phone GPS speedometers are not rocket science accurate either. If you drive a "Known mile" at 60 mph, it should take exactly 60 seconds to travel that one mile. :headbang:

 

[KarNut46]

Whatever the outcome this is an interesting problem. Let us know the solution.

 

[747mopar]

I agree with everybody else, I would turn 3,100 rpm on the freeway at 70 mph with 3:55s and 27" tires so yeap somethings off! I will tell you that adding an overdrive is the best thing you can do to add more joy to your ride. Although I didn't use the Gear Vendors I did install a Viper T56 and absolutely love cranking 1,800 rpm @ 80 mph haha.