Laycock J-type Overdrive

[1940 Dodge VC]

A lot of us want to keep our trucks as original as possible and, at the same time, improve the safety and performance to drive comfortably on today's roads. Along with brake upgrades, wringing more horses out of our flatheads, adding seatbelts and tightening up our suspension components, many of us have asked--how can I cruise at 65 while keeping the RPMs in a decent range? The three "big" solutions that stand out are a- swap transmissions for something with an overdrive, like a T-5 or an A833, b- swap rear ends, or c- add an overdrive, such as a Laycock. The problem with a- is that the engine may need to be pulled, an adapter plate might be required, a new hole in the floor must be cut and then there is the clutch... and what about the parking brake? The second option, b- presents the problem of gearing that is too tall for the torque output of the engine, especially if the flathead is wimpy,  such as a 201. So... c- was the option that I was most interested in. No modifications needed for the parking brake, transmission or engine. Gear Vendors sells a unit, or you can opt for the route I followed: find a Laycock J-type from a donor Volvo. Here are the modifications that I did:

The old truck came with the factory optional, slightly more desirable 4.10 ratio rear end (as opposed to the 5.63 stock rear end), so it could putter happily at 45 MPH and, sounding like a manic sewing machine, hit 65 MPH. I wondered about switching out the rear end—and had picked up one that was a 2.80:1 ratio. After doing a few calculations, I realized that the rear end would make the underpowered engine even more so. Maybe an overdrive would be better? I began a search that led to a Laycock model J overdrive, about the size and shape of a small watermelon. It fit nicely in mid-frame. I installed two drive shafts, one from the to transmission to the overdrive, the second from the overdrive to the rear end. It is important to mount these with the correct angles to preserve the u-joints. I also had to move the gas tank over by about an inch to fit around the overdrive. That wasn’t such an issue—the tank needed to be replaced, anyway. 

The Laycock overdrive is common on older Volvos. These are often listed on ebay—without the front drive shaft. I found a complete one, cut off the end of the shaft, and had a local machinist weld a u-joint receiver onto the end to accept a short drive shaft connection to the transmission. I fitted an aluminum plate with an oil seal for the front end of the overdrive unit. Ran a 12 volt wire to a fuse and button mounted below the dash--and added a pilot light that shows when the overdrive is engaged--and that was it. Simple! (an aside: make sure that the overdrive isn't engaged when putting the truck in reverse)

My biggest issue was with the speedometer output shaft. The truck cable housing wasn’t long enough to reach and the knurled connector didn’t fit. I am working on an alternative, though. A sensor connected to an Arduino, to read the speed and drive a little electric motor connected to the speedometer head… I’ll probably use a GPS to provide the speed signal.

BTW, in the process of putting the overdrive in, I discovered that the parking brake drum had developed a number of fractures and was close to exploding into fragments, so I replaced the whole arrangement with a snowmobile mechanical disc brake. That set up works very well for my purposes. 

Another tip: I put Lucas transmission oil additive—the stuff that you see on the car parts counters—into the non-synchro transmission and it worked so well that, for most of the gears, I can shift as if the transmission is synchro. Very nice.  

So, does the new setup work? Oh, yeah--I say with a big smile on my face. Oh, yeah, it is very, very cool. My 201 has no problem running the overdrive, and as a side benefit, I get an extra gear in 2nd and 3rd that makes puttering around town a lot more fun. Plus, the overdrive makes it easy to downshift without double clutching. I can wave to people as go around corners!

Here are the pictures:

 

[Plymouthy Adams]

I know I have one of these here at the house...but will remain with the original setup....like the write up....

[Don Coatney]

Innovation in UN-charted territory. First such well documented swap I have seen in a Mopar flat head. Great job. Looks like it grew there. Thanks for posting. 

[David A.]

Thanks for the good write up and pictures. I'm staying all original for now, but may go with this in the future. I replaced my 4:10 with a 3:54, but that will limit what I can pull. 

[Mike36]

Good job! I can see you are a creative thinker.

[NiftyFifty]

Very cool, not sure how it really keeps any more originality then slipping  a T5 in, and looks a lot more labour intensive, but your correct on pretty much needing to remove the engine to do the trans swap.

very interesting, thanks for the write up

[Young Ed]

10 minutes ago, 4mula-dlx said:

Very cool, not sure how it really keeps any more originality then slipping  a T5 in, and looks a lot more labour intensive, but your correct on pretty much needing to remove the engine to do the trans swap.

very interesting, thanks for the write up

Only thing that comes to mind is it lets you keep the original rear which on bigger trucks lets you have original looking wheels. 

[The Oil Soup]

Is there a way to mount it directly to the trans and eliminate the short driveshaft?

[Jeff Balazs]

Very nice conversion/upgrade. I really like those laycock units. Had one in a Healy, a Triumph and a Volvo and they always worked great. And being able to split the lower gears is a nice side benefit. I might consider this. I have a 230 with a 3.55 final drive ratio which works well. Being able to split 3rd would be nice though.

I have a little GPS speedo with a heads up display that is spot on. Very easy to read day or night and you don't have to look down.

Jeff

[John-T-53]

Very interesting, and thanks for sharing. Uncharted territory for sure! This is what you'd call a "divorced-mounted OD" or at least that's what Gear Vendors call theirs when set up this way. I have never heard of these units. Were they substituted for the tail shaft of a Volvo trans? What is the price range for finding one of there? Before I did my trans swap I was looking at GV but the price was way too high.

I assume this is a planetary unit, and solenoid engaged?

How did you design the crossmember/mount?

 

Edited June 30, 2017 by John-T-53

[1940 Dodge VC]

The Dodge VC has a large cross member a couple of inches behind the transmission tail that would be in the way of mounting the overdrive directly to the transmission.

As to the T5--I wanted to keep the whiny, grindy nuances of the original non-synchro transmission,  the thin shifter that sprouts from the floor, and the mechanical clutch setup.

When the laycock is not engaged, the truck functions just as it would have 77 years ago, and looks just like it came off of the farm. It is a great bridge to experiencing pre-WWII technology.

[1940 Dodge VC]

I got the overdrive about four years ago via eBay. At that time, it was a couple hundred dollars. The trick is to find one with the front shaft still attached. There are a lot of these around, so you should be able to find one at a wrecking yard. Google Laycock J-type overdrive to get an idea of what they were put into and how they work. 

To mount the OD, I removed the truck bed, then ran a support from the mid cross member to the back cross member, next to the gas tank on the left side. The tank had to be moved over by an inch to the left. Mounting: Use rubber bushings at each of the mounting points. Tail: The OD tail mount is on the bottom. Brackets were hung to accommodate the tail. See the pictures for an idea of how it was done. Front: I drilled and tapped the front aluminum plate for 3/8" bolts, then dropped brackets alongside the front to line up with the OD. The aluminum plate was what I used to cover the front of the OD. It was drilled to accomodate an oil seal for the shaft. 

One suggestion is to refresh the OD with new O-rings before installing it. It is a simple job, and is important for creating the hydraulic pressure that is needed to shift from high to low.

It is also a good idea to drill a vent/fill hole near the top of the OD adapter case.

[The Oil Soup]

What is the ratio when the OD is engaged?

[1940 Dodge VC]

Here are some numbers based on old notes and spreadsheet calculations. Now that the truck is running, I'll connect an RPM guage to verify these values. The "seat of my pants" calculations tell me these are pretty accurate.

OD 1 : 0.73 (it could be 25%)

Tire diameter: 29.5

Rear 4.17 : 1 (based on my notes--it may be 4.10)

MPH                      45           55         65        75

RPM 4th gear      2138       2613     3088    3564

RPM Overdrive    1561       1908     2255    2651

[Plymouthy Adams]

Per my Volvo workshop manual, OD is .756:1 so I would say you ball parking at .75 is a good number for now...

Edited June 30, 2017 by Plymouthy Adams

[pflaming]

I showed this sketch to  Dodge to confirm it correctly represents what he has done and he approved the sketch. I will definitely put one of these in my truck. A fantastic idea, TKS. 

     In regard to the U joint angle, I wonder if that is achieved and maintained by the lengths of the two mounting brackets.   JMO.  Dodge can answer the question. 

 

Edited July 1, 2017 by pflaming

[Matt Wilson]

How did you determine the correct angle to prevent u-joint issues?  I realize, for any given driveshaft, it's best to have the angle of the front u-joint the same as the angle at the rear u-joint, but how do you measure these angles and then adjust your setup to achieve them?  I can maybe envision putting washers under the bolts that mount the OD to the crossmember, to achieve different amounts of tilt, but I think that would be only for fine-tuning.  It seems that the mounting bracketry would have to be fabricated fairly close to the final product to start with.

I have a '49 Power Wagon, and this would probably be the ultimate solution, allowing me to take advantage of low 5.83 axle gears when I want them, but also allowing me to cruise freeway speeds when I want to.  Of course, I would have to fork over a bunch of money to install 5.83's, because I already have 4.89's in both axles.

Nice job, by the way!

[Matt Wilson]

Another question:  You mentioned using Lucas transmission oil additive and how nicely the tranny now shifts.  What gear oil do you use?  I am planning to try synthetic in my non-synchro 4-speed, which is probably just about like your 4-speed.  I've read about "silky-smooth" shifts in these gearboxes when using synthetic.  Maybe it's worth it for me to look at the Lucas product on top of that.

[Don Coatney]

 

[1940 Dodge VC]

Thanks, Don, for the drive line images!

I'm using Mobil 1 synthetic gear oil, 70-90 wt with the Lucas additive as per the instructions. The stickiness of the Lucas additive helps slow the gears down between shifts, so it isn't always necessary to double clutch. For example, I don't have to double clutch between 1st and 2nd--it shifts pretty much like a sychro. Usually I double clutch between 2nd and 3rd, though.

Matt, the key to making the drive shafts work correctly is to keep the overdrive parallel to the engine and rear end. Your connecting angles on a drive shaft need to be the same on the input and output side. The OD It does not have to be in the same plane as the engine, but to keep the drive shafts balanced, it needs to be parallel to the rear end and engine. That provides some nice options. For example, the overdrive can be offset a little to the passenger side to avoid having to move the gas tank. 

Since so many have asked questions (actually, I was pretty surprised by the response!), I'll work up some numbers for you. Will have to wait until Monday, though. My daughter and new son in law came over to help clean up. They had their wedding in our barn last fall.

BTW, you might want to check what your rpms will be with this setup and the 5.83 axles. Plymouthy Adams gave a value of .756:1 for the overdrive, so an approximation would be that you would reduce the rpms by 25%. I made a simple little calculator for that purpose. Will attach the spreadsheet document below.

 

RPM calculator.xlsx

Edited July 1, 2017 by 1940 Dodge VC

[Plymouthy Adams]

On ‎6‎/‎30‎/‎2017 at 0:13 PM, John-T-53 said:

Very interesting, and thanks for sharing. Uncharted territory for sure! This is what you'd call a "divorced-mounted OD" or at least that's what Gear Vendors call theirs when set up this way. I have never heard of these units. Were they substituted for the tail shaft of a Volvo trans? What is the price range for finding one of there? Before I did my trans swap I was looking at GV but the price was way too high.

I assume this is a planetary unit, and solenoid engaged?

How did you design the crossmember/mount?

 

if anyone ever in the past that looked into anything Gear Vendors would know that they are a basic copy of the Laycock de Normanville  unit that is quite the ticket in Europe for OD applications in many vehicles...the list would be shorter to name a company that never used this unit.

Edited July 1, 2017 by Plymouthy Adams

[Matt Wilson]

Thanks for the diagrams, Don.  We're saying the same thing, but it's clearer the way you presented it (i.e., thinking in terms of keeping the shafting parallel amongst all the various gear units) than the way I was stating it.  

1940 Dodge VC, what's still not clear to me, is how a person achieves the parallel shafting in practice.  If I was lucky enough to find that all my gearboxes (trans, OD, differential) have an external flat area that is parallel to the shafting, then that would help, but I doubt that's the case.  I guess maybe I have to measure the input and output shafts of each unit from some common reference plane (e.g., a flat garage floor for vertical direction, and the frame rails for the horizontal direction)?  Maybe I'm making this too hard.  On my Power Wagon, of course, I won't be dealing with the transmission output, but rather the transfer case output, but the concept is the same.  I was thinking the VC trucks were also 4WD, were they not?  So I suspect you are also dealing with the transfer case?

I must say that I am intrigued by the prospect of putting this OD in my Power Wagon.  Quite a few folks have put Laycock OD's in their Power Wagons, but most of them purchased a unit with pre-fabricated bracketry from a guy who used to offer such kits.  I was interested in doing that as well, but the gentleman retired and I wasn't sure how to go about doing it myself.  With your description and maybe a few other answer questions along the way, I might be able to do it.  At the very least, it will be something for me to consider, especially now that I know they are so readily available, for just a couple hundred bucks or so.  Of course, I have wonder what condition they are in, if the seller is only asking $250 - $350.  And it sounds like finding a unit with the input drive shaft included may be the difficult part.

Are these units capable of handling the torque from a moderately hopped-up 265 flathead, along with the granny gear torque multiplication that I get from my 4-speed transmission?

It looks like your ground clearance after install of the OD unit is not any less than before, either.  By that I mean the OD doesn't seem to hang down any lower than the gas tank or some other things around that area of the truck.  Am I seeing that correctly?

As for checking RPM's with setup, yes, I have done that, and with my gearing and tire size, the engine would be running at about 2600 rpm at 65 mph.  That is, after swapping my axle gears from 4.89 back to the original 5.83:1 and installing the overdrive.  That would be a very nice, comfortable cruise RPM for that engine, I think.  At 60 mph, the engine would be at about 2400 rpm.

Thanks for the answers.  I'll be here when you get time, but enjoy your family time together.

Edited July 2, 2017 by Matt Wilson

[1940 Dodge VC]

We're insulating the shop right now--I'm excited to have a space that can be heated in the winter!

 

Here are some quick responses. The civilian version of the VC did not have 4WD, though as I understand it, Dodge used that model as the basis for their military truck development, including 4WD.

You'll need one reference line which can serve for both the vertical and horizontal measurements. Run a stringline along the top center of the frame. You can verify the centering  by measuring across the frame at various points and taking half of that value as the centerline.

Finding vertical: Find the flat spots on each component, use an inclinometer (Amazon sells one for $7-- IRWIN Tools Magnetic Angle Locator (1794488)) to verify the vertical alignment. You could also use a digital level. 

Horizontal: Use the stringline and use the input/output shafts to align to that centerline. That line can also be used to put in the parallel supports, which can be used as the reference points for all your measurements. I would focus on keeping the OD parallel to the engine. 

It sits about the same level as the fuel tank, maybe a bit higher. Will check tomorrow.

Let me know if this makes sense.

[Matt Wilson]

Thanks!  I think it makes enough sense that I can figure out further mounting details as needed.  I may have to start perusing ebay to see what's out there.

Also, good move on insulating the shop. I insulated my garage a few years ago, bought a heater for the winter, and just finished installing a 240V air conditioner for the summer.

Edited July 2, 2017 by Matt Wilson

[1940 Dodge VC]

Happy 4th of July!

Here are some notes about the overdrive:

Laycock OD's come in several varieties. The designations of A and D were for early overdrives. J-type is the most common version and was used up through the 80's. The final model is known as the P-type. It is quite similar to the J-type and is used in some heavy duty applications, like racing. GearVendors bought the tooling rights for the P-type. (source: https://www.hemmings.com/magazine/hsx/2012/05/Laycock-Engineering/3712361.html) You can find a lot of information on the GearVendors website: http://www.gearvendors.com/install.html, and a testimonies about what it can handle.

http://maximum--overdrive.com/index.html is another source for Laycock overdrive kits. They sell parts, including the shaft for $245. The site also features some electronic over-ride ideas and a kit.  

If you purchase an used overdrive, it is a good idea to replace the O-rings. I purchased a kit from Duane at ODGuru@kc.rr.com. My notes say that it cost $50. His diagrams and instructions are quite good. It is an easy job that can be done in less than an hour.

There is a thread at http://www.mtfca.com/discus/messages/118802/120814.html with a discussion of fluid levels and types. My overdrive came out of a Volvo, so I am running Type F ATF.

Obtaining an input shaft is the tricky part. The resellers on ebay usually pull the OD from the transmission leaving the shaft behind. You may have better luck finding a shaft at a local wrecking yard.  Cut it off where it leaves the transmission. All you need is the part that fits into the overdrive and a couple of inches to attach the u-joint. You'll need the adapter collar (a 4" piece that connects the OD to the ) transmission. An enterprising person could manufacture the shaft. A spline on the end, an eccentric, a couple of clips and that is it.

You might consider Maximum Overdrive's shaft. It may be less expensive than cutting one off of a donor car and welding a u-joint on. If I were to do it again, that's how I'd go. 

These were used in many, many vehicals. An extensive list of Volvo model transmissions noting the "electric overdrive" is at http://www.nuceng.ca/bill/volvo/database/sources.htm#[GRIMSHAW96]. 

Okay, the dimensions! These are for the Laycock J-type, mounted on a 1940 Dodge VC. Your frame measurements may (will?) be different. Caveat: These are approximate, taken from the mounted OD while lying on a creeper  as the sun rose this morning.

Length: 19” from u-joint mount to u-joint mount (3/4” custom mounting plate on front, 1/2” custom oil seal on mounting plate, 4” collar, 9 1/2” OD ) 

Height: 7 1/2” max

Width: 7” max

Mounting measurements: My transmission measures 12” from the bell housing to the universal mount. Shaft (with universals) from the transmission to the OD, 21”, from rear of OD to rear end: 25" 

From the top of the frame to the centerline of the OD: 8.5”. The bottom of the OD is flush with the gas tank.

Passenger side to centerline: 20 1/2” on to the rear centerline, 18 3/4” to the front centerline (my frame angles in under the cab). Plenty of room to offset the OD without having to move the gas tank.

 

Edited July 5, 2017 by 1940 Dodge VC