Laycock J-type Overdrive

[1940 Dodge VC]

Here are some more pictures of the installation:

[Matt Wilson]

Wow, excellent information!!  Thank you so much for posting this!  It's good to know that parts to rebuild these are still available.  I guess it makes sense, considering so many were built.  If I go this route, I will probably buy the shaft from Maximum Overdrive.

I wonder what the likelihood is for getting a $300 - $400 unit off Ebay that doesn't need any significant repair or parts replacement (aside from the seals you mention).  Do you know if there are any difficult aspects to completely rebuilding one if these, if required?  I suppose overhaul manuals are available.

Thanks again.

[Matt Wilson]

By the way, I'm sure you know this, but others may not.  The vehicle must not be driven in reverse, or allowed to roll backwards with the overdrive engaged.  There's a sprag or overrunnimg clutch type of arrangement that apparently will be destroyed if operated in this manner.  This is based on other research I've done in the last couple of days.  The cars equipped with these OD's were setup with electrical lockouts and such, which prevented this type of thing from happening.  One could install something similar in our old vehicles, if desired, or at least a bright light on the dash to shiw when it's engaged, to serve as a reminder not to put it into reverse.

Also, I understand the OD is not really meant to handle the torque generated with the transmission in the lower gears, and probably should only be used when the trans is in high gear.  I read that the clutches will wear out somewhat prematurely, otherwise.

[greg g]

I had one in a late 80's Volvo wagon.  It was engaged by a button on the shift lever.  As I recall it would only engage when the shifter was in 4th position, likely a micro switch or a completion of the relay ground.  In any case, moving the lever out of 4th kicked the OD out so no worries regarding selecting reverse while engaged.  To enter OD one simply let off on the gas and thumbed the OD.  I do not recall if there was a kick down at wide open throttle.  The turbo made wide open throttle in 4th pretty much superfluous on the interstate.

I recall the OD ratio was in the 70 - 75% range which gave around 2200 rpm at 70 mph.  It was a J labeled unit.  They seem to be in the $200 to $300 range depending how you source them.

[pflaming]

I have an extra 218 engine and transmission so I will research to determine if it will fit in my 39 Chrysler, if so then I'll put in this overdrive. I will then store the original engine and OD transmission to assure someone down the road can revert. 

[bones44]

I have had a Laycock J type mid mount OD in my 1976 Ford F250 with a 5.9 Cummins diesel,BW T19 trans and 3:73 rear since the early 90’s. I used it to pull a flat bed goose neck with a 6000lb antique JD pulling tractor and never had any trouble splitting the lower gears.

[1940 Dodge VC]

If you get the o-ring kit, you'll also get some very nice images of how to rebuild the OD. It is a very simple procedure. There just isn't much to these units, and not much to go wrong unless you put the seals in incorrectly--generally, either the electric solenoid goes bad, or the hydrauling unit needs the o-ring kit. It is possible that the clutch material may wear out. The gears are pretty much bullet proof, unless they are sheared off by a load, and it would have to be a really big load... I've never heard of anyone blowing one up. I have two units and both seem pretty solid.

There are a lot of warnings about putting them into reverse, so I'm going out of my way to see that it doesn't happen. I have a dash light that reminds me when it is on. I may add a brake or clutch over-ride as well. Maximum Overdrive has a schematic for a brake override to protect the OD. Anytime the brake is engaged, the OD shifts back to low. You could also put it on the clutch, which would be more useful, I think. Anytime the clutch is engaged, the OD shifts to low. If you are really enterprising, you could mount a reverse switch to the end of your transmission. It would take a little engineering to find the right spot...

Last thing before watching fireworks  is that the hydraulic pressure is created by the input shaft RPM. It drives an eccentric cam that pumps a little hydraulic piston in the OD. The pressure that is created is used to shift from low to high. The electric solenoid, when engaged, routes the fluid to the pistons. The reason that the OD isn't used in lower gears is that if the shaft isn't turning fast enough, there won't be enough hydraulic pressure to shift or maintain the high speed position. That depends in part on the condition of the o-rings and the viscosity of the fluid that you are using. I've used it in 1st (accidently!) without any troubles. I especially like using it on 2nd and 3rd.

Happy 4th, everyone! A great day to celebrate the birth of the USA! Our founders, when signing the Declaration of Independence, knew they were signing a declaration of war. They hoped it would lead to a new republic, of the people, by the people and for the people. I'm sure they would be amazed, and blessed, to see how freedom has changed the world. We say "thank you" to our founders, and thank you to all our service men and women--actively serving and retired--for giving us peace and protecting our independence.

[John-T-53]

On ‎7‎/‎4‎/‎2017 at 11:34 AM, pflaming said:

I have an extra 218 engine and transmission so I will research to determine if it will fit in my 39 Chrysler, if so then I'll put in this overdrive. I will then store the original engine and OD transmission to assure someone down the road can revert. 

Why would you have to change engines? With this unit, you can leave everything in place...that's the advantage of it.

[Matt Wilson]

Thanks again for the info.  I'm still contemplating this, but will probably have to put it on the back burner for now.  I have enough expenses (and labor) associated with the other things I'm doing to my truck at the moment.  I think I need to get it up and running first and then see where things stand before I take on another significant job, but the OD still intrigues me.  I'll be interested to hear people's experiences with installing and driving with these OD's.

[1940 Dodge VC]

It is August 2018 and I've been running the overdrive for three years without a bit of trouble. Once in awhile people ask how I like it and I can say, without hesitation, that it is fantastic. The truck works like it originally worked (well, it is quite a bit safer-- I switched to disc brakes) , and with the press of a button, reduce the rpm's by 25%--so I can go modern speeds without blowing the engine. The one upgrade that I made was to attach a sensor to the clutch so that whenever the clutch is engaged, the overdrive shifts down (shuts off). That has turned out to be pretty handy for downshifting as I come to a corner (I simply press the clutch pedal half-way down and the OD disengages, shifting down by 25%), and for having a middle gear between 2nd and 3rd. So I go 1st, 2nd, 2nd OD, 3rd, 3rd OD. The clutch switch shifts the OD back to the off position between 2nd OD and 3rd. It also insures that the overdrive is never engaged in reverse or when starting in 1st gear . 

 

[p15-1948]

Looks like this modification will require a change to 12 volts?  Thanks

[1940 Dodge VC]

The short answer is yes... if you are running the 12v solenoid. 6v versions were also made. You could contact a Volvo dealership (or GearVendors--who owns the rights to the Laycock ODs) to see if a 6v version is available for for your OD, or you could use a 6v to 12v step up converter to send 12v to the solenoid without changing the vehicle's voltage. As to positive or negative ground--it shouldn't be a factor.

 

For the 12v solenoid: The resistance is unofficially listed as 17 ohms. Based on 17 ohms, the 12v circuit would consume 8.4 watts and draw 0.7 amps. If you run the 12v solenoid at 6 volts, then the solenoid would only draw 0.35 amps--2.1 watts of power. You would drop from 8.4 watts to 2.1 watts, and the solenoid probably wouldn't engage.

 

If you have a 12v solenoid but your vehicle runs on 6v, then you could put a 6v to 12v step-up converter in the circuit line to the solenoid. These converters are fairly inexpensive, running somewhere between $15 to $45. Just make sure that it can handle the wattage. Here is one on Amazon that could work for you: https://www.amazon.com/DIGITEN-Converter-Regulator-Waterproof-Module/dp/B019GY2FLW/ref=sr_1_5?crid=1UE2OHRME4KFY&dchild=1&keywords=6v+to+12v+step+up+converter&qid=1610727027&s=electronics&sprefix=6v+to+12v+ste%2Celectronics%2C167&sr=1-5 

Edited January 15, 2021 by 1940 Dodge VC

[JSabah]

Hoping to revive this topic a bit as I’m in the process of adding a Laycock overdrive to a ‘59 Dodge Power Wagon and have a few questions for those who have done this. 
 

1. is there any torque on the unit /brackets? I’m wondering how stiff or soft the isolators should be and what material to make the frame out of. My Laycock has threaded holes for 3/8 coarse and Moss and those that sell isolators are 5/16 fine for some reason. McMaster Carr has several that will work but they range in weight rating (ant torque) from 75 lbs up to 300 lbs (weight). 
I plan on making a bracket /mount for the front addition To using the tapped holes at the rear- are both needed? 

2.  Attached is a pic of my setup (temporarily being held and aligned by wood blocks). As you can see, I’m using a flanged yoke and u joint to connect directly to the transfer case. My concern has to do with alignment. Right to left, I’ll pull a string line and put the OD in line but the vertical angle is what has me confused from reading this thread. I was going to angle the OD as if it were just replacing the drive shaft but now think it should be at either the same angle as the TC or ??? (Just confused). Thanks in advance. 

 

[1940 Dodge VC]

That's a beautiful stetup and restoration! I don't have torque specs per se, though I am quite certain there is significant torque on the unit. Newton's 3rd Law... whatever torque is applied to the drive shaft will also be applied to the overdrive ?. The rubber isolation bushings on my setup are fairly stiff. Four bolts in front and two in the back. As to the angles-hopefully a driveshaft expert can chime in on this thread. I'm a little rusty on what the angles were. I do know that the geometry is critical to a balanced, smooth, quiet, trouble-free ride and to the longevity of the universal joints. I had help on that part from a driveshaft specialist in the area.

[1940 Dodge VC]

I just re-read your post. On my setup, overdrive is parallel to the transmission. Parallel, but offset so that the universals can be flexed correctly. My setup has a jack shaft between the overdrive and the transmission, so it is a little different in that sense. The overdrive had to be parallel to the transmission so that the universals would have the same degree of offset. As I recall, that was important to keep the setup balanced. Since your setup doesn't have a jackshaft, there will be some different rules to follow, and that's where the driveline experts will be quite helpful.

[JSabah]

Thanks. 3 months ago, the floor was clean and the frame was a mess ?. 

[JSabah]

Hoping a u-joint/drive shaft expert (or just about anyone cause most know more than me on this subject) will chime in here. I measured the angles of my components with a angle finder as described above (see below). At what angle should my OD be?

 

i will probably Ave to re measure as the rear axle has recently been off for leaf spring, axle and brake refurbishment and it has yet to be put down on its Rear wheels yet

[1940 Dodge VC]

I'm thinking that the H.A.M.B. board should have some driveline experts that could give some wise input.

 

Here is a general information site that will help with the geometry: https://4xshaft.com/blogs/general-tech-info-articles/driveshaft-angles

 

Here is another site that goes into a lot of detail about custom setups. https://www.therangerstation.com/tech_library/pinionangles.shtml

 

In both of these articles, the universals are paired on the shafts, that is, there is an input and output universal joint. They are also phased. In your application, the front universal is a single one, being used as a flex joint. The big question is whether it is okay to use a universal joint that way. The rest of the geometry isn't a problem so long as things are parallel and the angles are within the correct limits. Its that first universal that has me puzzled.

Edited March 23, 2021 by 1940 Dodge VC

[JSabah]

Interesting article. I need to digest it a bit more but the second to last paragraph lists different factors .... one of which is how smooth you expect your ride to be going down the highway..... it’s a Power Wagon , so not too ?.  Thanks. I’ll also look at the hamb- great idea. 

[Lingle]

I just went through the same thing with my conversion, trying to find the right drivetrain angles.  the sites above are great but I also used this site: http://www.billavista.com/tech/Articles/Driveshaft_Bible/index.html.  Since I am running a double rear driveshaft like the factory B3F 152 had, but hanger bracket had to move, spent much more time moving the rear axle pinion angle to get everything right.  What I have found is that for ideal life of the u-joints, you want to be <3° operating angle but something >1°.  There is a debate on running 0-1° angle, but most say in order to self lubricate you need at least 0.5-1° of angle for the u-joint but above 3° the life of the joint declines(unless you are using a double cardan style, common on front driveshafts for 4WD or some rear transmission output driveshafts).  

 

Dont forget the driveshaft angle itself plays into the deal, not only does the angles of the components but also the angle of the shaft plays in since you look at total u-joint angle between the component(axle, trans, etc.) and the connecting shaft.

 

[1940 Dodge VC]

That's a great site! I'm thinking that JSabah has three options: 1) Connect the overdrive directly to the transmission using a correctly sized flex disc or flex coupler--The overdrive would have to be aligned with the centerline of the splined shaft of the transmission. 2) Replace the forward u-joint with a CV joint that could handle his load, or 3) position the overdrive farther back, connected to the transmission through a jack shaft. (The third option is how mine is set up).

[JSabah]

I think I have the angles correct and now I’m thinking about a lockout switch for the reverse rail on the transmission (NP420). I’ve found plenty of info on installing a brake light switch- which I believe should be normally open. I’d like to install a normally closed switch on the reverse rail so that power can be sent to the solenoid when in any forward gear, but that will open the circuit when put in reverse. I can’t seem to find what I’m looking for. Can someone point me in the right direction? Thank you

[1940 Dodge VC]

This can be solved without changing the brake reverse light switch. Place a relay in the brake reverse light circuit to disengage the OD whenever the reverse light is engaged. Here is a description of the circuit--My assumption is that the power to the reverse light switch comes from a fuse to the reverse light switch, and from there, it goes to the reverse lights or ground. 

 

Power to the OD: Run power from your OD switch to pin 30 on a typical automotive relay (12v--though you may be running 6v, in which case, you'll need a 6v relay) . From the NC (normally closed--or the de-energized side) of the relay (labeled position 87a) run the wire to the solenoid on the OD. This setup powers the solenoid when the the switch is engaged. NOTE: In some applications, the OD switch is connected to a separate relay that powers the OD. It is the power to the OD that needs to be connected to pin 30.

 

Now for the reverse light switch: Route the + reverse light switch wire to the relay coil (85).  Run a separate wire from pin 86 to ground (instead of routing the wire to the reverse lights). The coil has enough resistance that only a trickle of power will flow through the relay when it is energized--not enough to light up the reverse lights--I'll get to that in a moment. Now, any time the brake light switch is energized, the relay coil is energized and the relay will flip to NO (open), disengaging the OD solenoid.

 

Reverse lights: If you are planning on installing or using reverse lights, you may need a separate solenoid... 

 

Here is a link for relay information: http://www.gtsparkplugs.com/intro-automotive-relays.html