TH-400/Gear Vendor OD driving impressions

Been doing a little driving now with that 72 STG 1 Convert we put the GV overdrive in.

I am impressed, to say the least.

While the manual engaugement is definately "crisp", when we put it into automatic mode, and let it simply function like a 4 speed OD trans, the electronics package shifts it smoothly, so much so that you hardley notice it happened.

The electronics activate the od, thru the use of a electronic speed sensor installed in the cable assembly, at about 42 MPH, automatically.

This car has the level 1AM motor, with our Level 1 TH 400/GV combo, and the orginal 8.5" rear end, with 3.73 gears. It's a column shift car. It is shod with 255/50 VR 16 wheels on all four corners. The tires are about 26" tall, and in high gear, without the od, it runs right at about 27-2800 on the factory tach, engauge the od, and it drops to right around 2100 rpm.

With the cam specs this motor has, it has very crisp throttle response at that rpm, I doubt I would want to slow the engine down much more, since there is no need to disengauge the od to accelerate around cars during normal driving. If I slowed it down to say 1800 rpm, it might be kinda a dog.. and you would have to disengauge the od to accelerate with any kinda spunk.

No MPG data yet, as I have only driven the car 12 miles (between snowstorms) :rant:

I will post some pics later, but I will tell you guys, that even though it requires some tunnel mods to fit, it was really nothing life-threatening, and now that everything is installed, it looks very much stock from the inside, under the hood, and even under the car. I fit the GV pretty tight, and have had no trouble with it moving, and hitting the floor. This was an unknown till I drove the car.

While not the cheapest way to get an OD, with all things considered, I do believe this to be the best choice. One of the major advantages is you don't have to fool with shifters, TV cables, trans mount or location of that mount ect.


And it still has the virtually bullet-proof TH 400 in it. In this case, the numbers matching one. With all the correct VB/Governor calibrations, for this car.

I did install HRPartsN stuff double adjustable upper control arms, to get the pinion angle perfect, but it is my opinion that you prolly could get away without them.

I will say, having driven a lot of Big Block GS's in my time, with the addition of the following parts, I wish GM had built them all to drive like this.. it is a fantastic drive, with a firm but not harsh ride, and awesome handling and braking.

tall spindle conversion with BAER 4 wheel disc brakes,

dela-lum Global west bushings

GW upper control arms for the tall spindles,

Global West lower rear control arms, (no rear sway bar)

Global west lowering springs all the way around (car sits about 2" lower than stock, but with the low profile tires, appears to not have been lowered)

GW fast ratio steering box (just shy of 3 turns lock to lock)

And of course the big rolling stock.

Pictures later.

JW

 

Sounds VERY cool! :Brow:

 

Later my foot.

"Pictures later", No-don't do this to us Jim. We want pictures NOW! Please?

 

Hey Jim , Can you change when od comes in and out?I'm thinking about putting one in, i have 3.31 with TA288-94h and was thinking about what you said at lower rpm's do you have to manually shift out.At 55mph in od i would be 1600-1700.thanks for all the info

 

Patience is a virtue, my friend.. :laugh:

And with the dial up here at the shop, I would grow pretty old posting pics.. :boring:

Coming soon, just got to navigate home thru a snow storm.

JW

 

With automatic control.. no.. it turns on and off at 42 MPH (there is a delay built in, which requires that it stays below 42 for a time period, so it won't "hunt" if you happen to be driving along at 42..)

With full manual control, then yes, you can turn it off at any time.

With that cam, and those gears, I guess I would have to drive the car, to see how responisive it is at 1600 rpm in 3rd OD. it would depend on the converter, but you would have to have a pretty tight one, to be cruising along at 1600.. I'm thinking your going to want to switch the od off manually, for 'spirited' acceleration in high gear, at part throttle.. you will get a modulated 3-2 downshift at less than WOT, depending on your trans calibration.. and at WOT, the trans should automatically downshift at speeds under 65-70 mph, and while it would then still be in second-overdrive, it should accelerate just fine.

JW

 

on the bench

first

 

close up of the unit

Note the two hex head bolts on the top of the GV unit.. I eventually replaced these with button-head allen screws, as one of them was very close to the middle floor brace, after the install. That provided enough clearance, and I did not have to touch the braces.. just the floor pan itself.

 

Floor mod

And the modification in the floor to fit the unit.

 

What floor mod..

with pad and carpet, it's not visible.

And yes, that's all the hidden custom autosound stuff.

 

and the install pics

 

The unit clears the stock crossember with no mods, if just barely.

 

my finger is pointing to the tightest area, where the floor has to be clearanced.

 

Stretched the metal.

 

another

 

After the driveshaft was made up (they supply the front yoke) the X pipe exhaust was fabricated around the unit, to provide just the right positioning.

(it is centered.. angle of the pic is decieving)

 

You can also see the speed sensor, and the extention cable for the speedo. Later on the wiring was hooked up, and it was run right up the cable, to the inside.

To the GV control unit, which is hidden under the driver side of the dash. (blue arrow)

 

The manual control unit went into the glovebox.. we were going for a completely stock look, even with lots of extras.

This allows you to switch from manual to automatic modes, and the red light comes on when it's in automatic, the green light comes on when the GV is activated. Normally this box would go under the dash, if we were not hiding it.

 

And the manual switch, which turns the system on and off, is hidden under the carpet, just below the factory dimmer switch.

They supply another dimmer switch with the install kit, but we were in stealth mode.. this is the switch I sourced for the VP activation kit, it has just the right action so you can actually set your foot on it, without triggering it.. you just have to flex your toes a little, to trip it on and off.