GKN Overdrive

The Dro

Well-known member
The description for this overdrive unit reads as follows:

"The Overdrive is operated by an electrical solenoid controlled by a switch mounted on the customized gear knob. The unit can be engaged or disengaged without using the clutch pedal, as the unit was designed to operate when the engine is transmitting power.

An inhibitor is fitted in the electrical circuit to prevent the unit operating at unsuitable road speeds. The unit automatically disengages when the road speed drops below 30 mph and cannot be re-engaged until that speed is exceeded."

The part I'm interested the most is what I bold/underlined out... The electrical part I fully understand... Mechanical... not so much...

Does this means that you can use this with an Automatic Transmission without destroying the overdrive?
 

RBBailey

Well-known member
Callsign: KF7KFZ
I just looked this thing up—they have one for auto?

What is the price on these things?
 

The Dro

Well-known member
Wouldn't an overdrive on a V8 automatic put you out of the power band? Honest q
It depends on the transmission.

But... I have the parts to connect a TorqueFlite to the LT230. The TorqueFlite is a 3-speed transmission.

I just looked this thing up—they have one for auto?

What is the price on these things?
The ones I've seen are on the TD5. Devon4x4 only has parts. But on ebay UK range from $400 to $1,500.

The part number is DA4066
 

The Dro

Well-known member
+
Other than the electronic activation, why not go with a Roamerdrive?
I was interested because of this statement:

The unit can be engaged or disengaged without using the clutch pedal, as the unit was designed to operate when the engine is transmitting power.

and that I have the parts to mate the TorqueFlite.

I was told you cannot use the Roamdrive without using the clutch
 

RBBailey

Well-known member
Callsign: KF7KFZ
That’s true. You’d have to look at the trade off for parts and cost. Roamer is NA based, and are still being made. Price is probably not very different.
 

rocky

Well-known member
As a kid a company called Laycox sold an overdrive that was electrically controlled by the driver and fitted to MGs, Triumphs etc. GKN bought Laycox

Wondering if yours used a similar system-I just don't know. If they did, then this might help you: https://www.uniquecarsandparts.com.au/how_it_works_laycock_overdrive History: https://www.hemmings.com/magazine/hsx/2012/05/Laycock-Engineering/3712361.html
This is the kind of relatively useless information that I absorbed as a kid thanks to spending my pocket money on car magazines from the age of about 8 onwards.
 

Uncle Douglas

Well-known member
Have worked on and driven GKN trucks. Worked well althought the shifter button was problematic. Thought they were out of business years ago ?
Or is Pedro just tripping ?
 

rocky

Well-known member
Have worked on and driven GKN trucks. Worked well althought the shifter button was problematic. Thought they were out of business years ago ?
Or is Pedro just tripping ?
GKN stopped making them in 2007.
Anytime you have electrical switches and solenoids, you add opportunities for things to break. I prefer the KISS method anytime its possible. Same reason I went with a Detroit rather than an ARB for my locking rear diff all those years ago.
 

The Dro

Well-known member
Have worked on and driven GKN trucks. Worked well althought the shifter button was problematic. Thought they were out of business years ago ?
Or is Pedro just tripping ?
Why am I tripping? I just want to know if they work on a auto box.
 

Uncle Douglas

Well-known member
My recollection is that you had to turn it off. You can go through the gears with it on. IE there was no switch on the clutch pedal that disengaged it.
So seemingly it would work.
 

The Dro

Well-known member
My recollection is that you had to turn it off. You can go through the gears with it on. IE there was no switch on the clutch pedal that disengaged it.
So seemingly it would work.
Thanks... That's what I wanted to know. :)

Having an autobox is something that I'm thinking about.
 

Uncle Douglas

Well-known member
Begs the question, why do you think you need an overdrive if you intend to use a large 6 cyl or v8 engine and automatic transmission ?
Automatics today have 6 and 8 gears, designed to always be in the torque band.
 

The Dro

Well-known member
Begs the question, why do you think you need an overdrive if you intend to use a large 6 cyl or v8 engine and automatic transmission ?
Automatics today have 6 and 8 gears, designed to always be in the torque band.
That's a totally different question... :D
 

rocky

Well-known member
That's a totally different question... :D
Indeed.
Overdrives were popular when gearboxes only had 4 manual speeds. It wasn't until the late 1960's that five speeds started to arrive. That started the clock to overdrive's demise.
 

The Dro

Well-known member
This all came about when I saw Robert's I-6 conversion and the fact my back is not doing me any favors... So I was looking at (AT) options, like the TorqueFlite or the TH400.

Just an idea... I don't have time for a project. :eek:
 
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