Chuck’s Borg-Warner Rancho Overdrive thread

chuckyb · Feb 6, 2019

Hi all, I purchased a “Rancho Overdrive” last year and thought I would start a thread to share my experiences with it as I continue to do the work (and spend the money) required to incorporate it into my build. I am going to do this chronologically yet piecemeal due to time constraints so please be patient with me. I am certainly not an expert but want to share what I have learned as hopefully get some ideas along the way. I bought my unit from a CB member. I paid alot for it (over 1k) but kind of had to have it once I researched it. Here is how it looked when it arrived in the mail.

chuckyb · Feb 6, 2019

A couple more pictures of the unit as it arrived. It arrived with a solenoid that was disconnected, a speedometer cable and two engagement / release cables. Per the PO, it was missing a kickdown switch and an electrical relay. There is some good info on the Rancho overdrive on CB and around the internet, but not a lot. Although in the Bronco community, we refer to these as Rancho Overdrives, they are really a Borg Warner overdrive with an adapter manufactured by Rancho, so that the BW overdrive can mate to the back of the Dana 20. I learned a lot from Randy Rundle at Fifth Ave Internet Garage. Randy knows the BW OD in and out, and has actually published a small book about them. Turns out they were made from the 30s to the early 70s and used on all kinds of vehicles. The BW units used to be easy to find in junkyards, but are a more difficult find now. Rancho made only approx a few hundred of the adapters for the Bronco Dana 20 (I can’t find an exact number). They also made many more of them for the Jeep Dana 20 but they are different and not easily interchangeable. The first picture of this post shows a close up of the Rancho adapter with the patent numbers. The fourth picture with the 2 loose bolts and hole in the middle is where the solenoid goes.

SavageBurro · Feb 6, 2019

That's super cool. What sort of overdrive ratio?

triracer67 · Feb 6, 2019

Curious follower, mine used to have one of these, and I’m trying to find one to install.

chuckyb · Feb 7, 2019

SavageBurro said:
That's super cool. What sort of overdrive ratio?

Thanks. It is a 30% overdrive ratio. It kicks in at 28 MPH so in practical terms it should convert the 3 speed to five forward gears.

Pa PITT · Feb 7, 2019

That's kind of neat for sure. I'd almost think 30% might be a little too much . But that's what it is.
... You might check with a member here. His handle is AMAX.. He's a school shop teacher & He built an adapter for a diesel project .. I was very impressed when I visited with him about 5 times. But I'd think he could build that adapter in class & show the kids what he's doing .

garberz · Feb 7, 2019

How are you gonna address the added length in the drivetrain?

Mark

chuckyb · Feb 7, 2019

Pa - I have been wondering if the reduction is going to be a bit too much, also. I found an old advertisement that says the Rancho OD works best with a 4.11 rear, and I have a 3.50.

Mark - I had my original driveshafts from my 68, originally BW style. I had them rebuilt as Spicer style. At the same time, I had the rear driveshaft shortened by 9” to accommodate the length of the OD on the back of the Dana 20. I also added 2 degree shims to the rear axle to help with the pinion angle. Here is a picture of the rebuilt driveshafts.

Converting the driveshaft to the Spicer style has caused me issues. The yoke on the BW OD is Borg Warner style - no surprise there. I figured no problem, I will get a Spicer style yoke and attach it to the OD. I picked up one of the Dana 20 replacement yokes that the vendors sell, then ran into the problem that the splines on the OD are different than the splines on the Dana 20. I addressed this with the guys that built the driveshafts and they couldn’t find anything that would fit the OD splines. As such they recommended sending out my replacement D20 yoke to get resplined using an EDM process. I did this and it wasn’t inexpensive. More on this later as I want to provide some pictures.

While I am at it, I’m including a couple of other pictures of the original BW yoke and some pictures of it getting cleaned and painted. I cleaned the OD unit out best I could by running diesel fuel through it. It still had some original paint on it that looked seafoam green. I like POR-15 and found that they have a Buick green engine paint which was somewhat close, so that’s what I used.

sykanr0ng · Feb 7, 2019

The popular 4R70W transmission has an overdrive gear ratio of 0.70 or in other words 30 percent.
So you could pick your final drive gears as if you had a 4R70W.

tirewater · Feb 7, 2019

It'll be interesting to get modern feedback on how well it works. There appears to be some differences in how it drives. It's hard to decipher what's true or not, such as does it really lack engine braking at sub 30mph speeds?

It's also interesting to note, that there definitely isn't as many 'nanny' aids in operation of the device. Such as someone trying to put the vehicle in 4wd while the OD is active. It appears knob out is inactive, and knob in is active (counter intuitive these days).

The operation of these things appears more complex than what I first thought.

rydog1130 · Feb 7, 2019

chuckyb said:
Converting the driveshaft to the Spicer style has caused me issues. The yoke on the BW OD is Borg Warner style - no surprise there. I figured no problem, I will get a Spicer style yoke and attach it to the OD. I picked up one of the Dana 20 replacement yokes that the vendors sell, then ran into the problem that the splines on the OD are different than the splines on the Dana 20. I addressed this with the guys that built the driveshafts and they couldn’t find anything that would fit the OD splines. As such they recommended sending out my replacement D20 yoke to get resplined using an EDM process. I did this and it wasn’t inexpensive. More on this later as I want to provide some pictures.

I ran into a similar problem on my 68. I sold the original 3 speed w/ transfer case as I was going with a c4. Well, the C4 dana 20 had spicer yokes and my original shafts were still BW's. I should have pulled the yokes off my original D20 before I sold it. Luckily I was able to source some OG BW yolks for the D20 and life was good again....

Could you have sourced another 67-68 rear drive shaft w/ yokes and had it shortened?

Click to expand...

DirtDonk · Feb 7, 2019

chuckyb said:
Pa - I have been wondering if the reduction is going to be a bit too much, also. I found an old advertisement that says the Rancho OD works best with a 4.11 rear, and I have a 3.50.

That's likely because most people with the 4.11's and 4.56's that were common back then, wanted taller gearing for the highway with those tiny tires that were also the norm back then.
And the 3.50 crowd just didn't need overdrive all that much even at high speeds.

Add to that smaller, weaker, carbureted engines, and low rpm pushing wind was not a desirable trait.
But a modern EFI setup, or much higher performance engine could change that completely.

What size tires, and what engine are you running?

Paul

DirtDonk · Feb 7, 2019

chuckyb said:
...It still had some original paint on it that looked seafoam green. I like POR-15 and found that they have a Buick green engine paint which was somewhat close, so that’s what I used.

That's a very cool color I think. Looks very industrial (and brand new too) and purposeful.
Would likely make a good Bronco color!

Paul

chuckyb · Feb 7, 2019

tirewater said:
It'll be interesting to get modern feedback on how well it works. There appears to be some differences in how it drives. It's hard to decipher what's true or not, such as does it really lack engine braking at sub 30mph speeds?

I have read that there is no engine braking when set up in a 2WD car below 28 MpH. I am having trouble getting my head around whether the same would hold true for a Bronco application when there is a D20 between the trans and OD. I just don’t know. And yes, I am worried that it won’t be idiot proof and I will destroy the needle bearings somehow.

chuckyb · Feb 7, 2019

rydog1130 said:
chuckyb said:

Could you have sourced another 67-68 rear drive shaft w/ yokes and had it shortened?

Click to expand...

Hey Ryan! I might have to explore this option. It might come down to parts availability and cost. I’ll provide more info and pics on my progress with the resplined yoke.

chuckyb · Feb 7, 2019

DirtDonk said:
What size tires, and what engine are you running?

Paul

Hi Paul, I don’t have them yet, but I am planning on putting BFG AT 30’s on my stock rims. The motor is the original 289 freshly rebuilt and mildly bored out. Glad you like the Buick Green, I think it’s pretty cool!

DirtDonk · Feb 7, 2019

chuckyb said:
I have read that there is no engine braking when set up in a 2WD car below 28 MpH. I am having trouble getting my head around whether the same would hold true for a Bronco application when there is a D20 between the trans and OD. I just don’t know. And yes, I am worried that it won’t be idiot proof and I will destroy the needle bearings somehow.

Not sure how it knows, or if this is just a generic statement by the manufacturer.
Either way, this relationship should not change just because there is another gearbox (direct drive) in-between.
However, the gear ratios in the differential will definitely have an effect, no matter what vehicle it's in, or whether there is even an overdrive installed or not. As would an automatic transmission vs a manual.
The taller ratios and larger tires naturally reduce the compression braking effectiveness overall. A lower gear ratio and smaller tires would enhance compression braking of the engine.

My '68 with it's barely 30" tall tires and 4.56 gears and an automatic transmission will pull the vehicle down literally to almost an idle speed with engine compression alone. Stock Explorer engine as well, so nothing exotic.
That's all gear ratio there, with maybe some help from a responsive 4R70W trans.

Your 3.50's would naturally have less overall braking effect.
I'm not really sure how a mechanical overdrive knows "miles per hour" anyway. Unless it's programmed to know the gear ratio and tire size, it has no idea what speed the vehicle is going.
So I'm guessing it's more of a generic statement.

Paul

DirtDonk · Feb 7, 2019

chuckyb said:
...I am planning on putting BFG AT 30’s on my stock rims.

Well, if the motor is a strong puller, those tires with that gear ratio might just be pretty sweet. Would be fine even without the overdrive frankly, but with it you might just have some extra fun on the freeways at higher speeds.

Ultimately there's only one way you're going to find out though. And that's to get 'er done and run it!;D

Paul

DirtDonk · Feb 7, 2019

Getting back to the gearing effect, if you were in 4-LOW range you would obviously have more engine braking when much slower than 28mph. So again I think it's just a generic statement of something to be aware of with regard to changes in how it makes the vehicle act.

And speaking of 4-wheel drive... You realize you can't use 4wd and the overdrive at the same time, correct?
It's not a big deal because you would not normally need it when doing something in four-wheel drive. But it's worth noting as a way of remembering to never have the OD activated when you need to lock in the front hubs, or put the t-case in 4WD.

I do think you can get away with the t-case locked in 4WD while the hubs remain unlocked, because all you're doing is spinning the driveshafts at different speeds but nothing is connected to the front to cause trouble until you lock the hubs.
And vice versa, if you happen to lock the hubs in, but leave the t-case in 2WD.

I don't know these things for a fact, so maybe others with more Dana 20 experience can add their thoughts to this. But that's how I see it.

Paul

Pa PITT · Feb 7, 2019

...AM I wrong .. But will you ever use O/D in 2nd or 3rd gear. I'm thinking the only time you'll use O/D will be when your rolling down the Hwy in 4th gear & t/c not engaged at those speeds .
... So I DON'T THINK YOU'LL EVER Get to that issue.
Now if my GRANSONS WAS to borrow it. I'm sure he'd pit it in 4x4 & O/D On the Pavement .. Because he's smart that way.
But you'll know your Bronco & how it works.
....................
... Or am I missing some point here.
............
.... I had a 1955 V8 265 chevy , 3 speed with an O/D . The solenoid did not work. SO It was always in O/D . With it I could take off in 1st gear ... then let up on the throttle & it shifted into OD WHILE IN 1ST. SHIFT INTO 2ND ... IT'D GO BACK TO UNDER DRIVE ... Then let up on throttle & it's shift up into O/D SAME FOR 3RD.
...........
... THERE WAS supposed to be a cable to work the solenoid & keep it down into under drive.
... BUT YOU WERE FREE WHEELING WHEN YOU LET OFF THE GAS OR THROTTLE. So you'd better have good brakes ...
It took me over 2 miles to roll to a stop when I had a brake line bust.

Chuck’s Borg-Warner Rancho Overdrive thread

Sr. Member

Attachments

Sr. Member

Attachments

Sr. Member

Sr. Member

Sr. Member

Bronco Guru

Bronco Influencer

Sr. Member

Attachments

Bronco Guru

Sr. Member

Bronco Guru

Bronco Guru

Bronco Guru

Sr. Member

Sr. Member

Sr. Member

Bronco Guru

Bronco Guru

Bronco Guru

Bronco Guru

Similar threads