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Old 07-08-2018, 10:36 AM   #1
Roderick
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Default Volvo Laycock Overdrive DIY

Hi, I have a 1929 Roadster with 5.9 head, reground cam, electronic ignition with centrifugal advance, and downdraft Weber 32/36 carb. I plan on installing a Laycock overdrive unit scavenged from a Volvo into my torque tube. For this project I will be enlisting the help of my machinist friend Steve (little does he know). I have found some good info but I would appreciate any input. I do have a couple of questions:
1. Can anyone help me understand how to set up the reverse lockout switch so I can avoid backing up with the OD engaged? (Bruce in Ma, Jason in TX?) Part number/source for the switch, how to wire, photos of switch location in transmission cover?
2. Has anyone found a way to correct the speedometer? Is there an off-the-shelf reduction gearbox for the speedo?
Thank you very much for any help in advance.
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Old 07-08-2018, 09:28 PM   #2
Kahuna
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Default Re: Volvo Laycock Overdrive DIY

Roderick
The speedometer comes off the OD, so no adapter/reduction is needed. Just a custom cable.
The best way to handle the reverse lock out would be to use a switch
located in the shift tower itself actuated by engaging reverse.
I don't know how it would be done on a Model A, but someone has done this, I'm sure.
For my car, I'm using a different transmission case and the shift tower has a backup light switch that I used to disengage the OD.
On my car, a 32 Ford, to wire the OD ( A Gear Vendors unit, similar to the Volvo stuff), I used a 60's OD handle and mounted it to a 2 position push/pull switch with an LED so that when the handle is pulled, the led illuminates and the circuit is completed so that the OD MAY be engaged (kinda like an arming switch). Then I have a momentary switch installed in the shift ball (A Volvo shift ball), to actuate/engage the OD. To do this, I bought a Marlin Model 66 .22 cal rifle barrel and ran the trigger wires down thru the barrel, exiting just before top of the transmission tower ( the rubber boot covers it). I had it chromed after welding and no one can tell the difference unless they know what to look for.
I assembled a set of 5 small Bosch relays to create a latching relay system, so that hitting the momentary switch engages the OD, hitting it again, disengages the OD.
This works real well, gives great mileage, etc.
You'll love the OD
Jim

Last edited by Kahuna; 07-08-2018 at 09:33 PM. Reason: sp
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Old 07-09-2018, 07:40 AM   #3
Roderick
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Default Re: Volvo Laycock Overdrive DIY

Jim,
You are an artist. The rifle barrel idea is completely inspired. Thank you for the reply. I would love to see a sketch of your wiring setup if possible. I would like to set mine up so that if I park the car and shut it down with the OD engaged, when I restart it the OD will be disengaged until I hit the button again. Does your setup do this? I am forgetful, so I want to idiot-proof it as much as I can. I got the idea from my buddy's table saw. We were ripping some nasty wood and it bound the blade, tripping the breaker. He reset the breaker without pushing the stop button on the saw and it didn't try to start again until he pushed the start button because it has a safety feature. I think it has electromagnetic contacts that keep it engaged. When the breaker shuts off, the electromagnet de-engergizes and the contacts separate. This plus the reverse lock-out should keep me out of trouble I think. Also, how do you drive yours? Do you split every gear? Do you find you need to be at a certain road speed or rpm for engaging or disengaging the OD? I have read that the shifts are slower at lower speeds since the output shaft of the transmission drives the pump that shifts the OD.
I am thinking that the reverse lockout switch could be a thread-in type with a ball that is pushed in by the shift rail in the transmission cover when reverse is engaged. I would love to see how others have done it instead of reinventing the wheel. Maybe there is a source for a switch that fits well without drilling a massive hole, etc. I don't want to experiment with drilling my shifter housing, or create a setup that is unreliable and kills my OD.
Thank you all for sharing your knowledge. Twenty years ago most of this information would have been difficult or impossible for me to access.
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Old 07-09-2018, 01:23 PM   #4
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Default Re: Volvo Laycock Overdrive DIY

Yes, When the Ignition is off, the OD is disengaged until the button switch on the shift ball is pressed.
I sent you an email
Jim
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Old 07-09-2018, 02:02 PM   #5
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Default Re: Volvo Laycock Overdrive DIY

There was a fellow named Bob Bell in Manteca , Ca. who built and installed OD's. He provided a short 1/4" dia.rod that connected from the OD case lever over to the stock A tranny tower. A hole was drilled in the A shift tower to the reverse shift rod and when engaged prevented the OD from engaging while in reverse though don't remember the exact configuration as this was in the early 1980's and have no records any longer. No electronics were required.
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Old 07-10-2018, 09:49 PM   #6
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Default Re: Volvo Laycock Overdrive DIY

Thank you very much for the replies. Yesterday I went to a junkyard and spent $197 on this used M46 Transmission with OD from a 1986 Volvo with 95,000 miles.

The OD unit seems to be stuck on the transmission right now. I read on another site that the way to prevent this is to start the car, engage the OD, push in the clutch, put the trans in neutral and disengage the OD while still holding in the clutch. If this is not done, the output shaft of the trans will be locked into the OD. The procedure to separate the two if the trans is already removed is to apply 12 volts to the solenoid, then remove a threaded plug near the solenoid and connect a grease gun to the hole with pipe fittings. The grease gun is to be filled with oil and used to pump oil into the hole which will move a piston in the OD, releasing an internal clutch which releases the output shaft of the trans. This should allow the trans to be separated from the OD. I will report back once I have tried this procedure.
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My grandma used to tell this story when she took me for a ride in her 1915 Model T Touring: "I didn't want to learn to drive the T, but your grandpa made me. We would be driving along and he would stand up at the wheel and say 'Get your a&& over here, you're driving'. What could I do? I slid over to the driver's side and took the wheel! I was afraid, but he made me do it. He made me strong".
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Old 07-15-2018, 08:03 AM   #7
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Default Re: Volvo Laycock Overdrive DIY

Here is a link to a detailed tech article on the Volvo overdrive. It was made by Laycock, a British company, and was also used on Triumphs and other British cars. This article discusses the J-type overdrive, which is supposedly more reliable. It details teardown and rebuild.
http://www.buckeyetriumphs.org/techn.../JOD1/JOD1.htm
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My grandma used to tell this story when she took me for a ride in her 1915 Model T Touring: "I didn't want to learn to drive the T, but your grandpa made me. We would be driving along and he would stand up at the wheel and say 'Get your a&& over here, you're driving'. What could I do? I slid over to the driver's side and took the wheel! I was afraid, but he made me do it. He made me strong".
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Old 07-15-2018, 08:07 AM   #8
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Default Re: Volvo Laycock Overdrive DIY

Here is another link to an official Volvo manual on the overdrive so you don't have to buy one on Fleabay.
http://pcbunn.cacr.caltech.edu/jjb/T...ive_type_J.pdf
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My grandma used to tell this story when she took me for a ride in her 1915 Model T Touring: "I didn't want to learn to drive the T, but your grandpa made me. We would be driving along and he would stand up at the wheel and say 'Get your a&& over here, you're driving'. What could I do? I slid over to the driver's side and took the wheel! I was afraid, but he made me do it. He made me strong".
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