T85 R/11 Borg warner 3 speed OD Manual Trans.

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T85 R/11 Borg warner 3 speed OD Manual Trans.

Post by Theo » Fri 2. May 2014, 12:01

Hi everybody. Not exactly a MEL transmission. I decided to put some cool info about the T85 R/11 Borg warner 3 speed OD manual trans as they might be of interest to all those who like to use it on their MEL race car project. The information was sent to me by a gentleman with the name of Hollis quite a long time ago. I'm not resposible for wether or not this content is complete, wrong or whatever it occurs to be. Hope you can extract as much good info as possible.

T85 C and N Overdrive

The Borg Warner R10 OD came out in 1934 and was used up through 67. R10s were made to adapt to other manufacturer's transmissions as well as their own later model T86 which was a light to medium duty trans. They had a small planetary with only 3 planet gears. In 1948 they started making the heavy duty T85 with the heavy duty R11 OD with a much larger planetary gear with 4 planet gears. It was used in late 40s/early 50s Lincolns, 55-57 T birds, full size Fords/Mercs with FEs through '64. All of these were the C model (at least the Ford/Merc/Lincoln ones were), and it was standard behind the '60 360 horse 352 hipo, the '61 375/401 horse 390, and optional behind 406s and 427s thru 64, although not many people know this. There were a number of OD tailshaft configuations, but the guts were all the same. From 1965 thru 72 they made the T85N for trucks. If you ordered up to a 3/4 ton 390 4 barrel Camper Special pickup with a 3 speed OD this is what you got. The N model case had both the narrow and wide bolt patterns on the mounting flange, an input shaft about 7/16" longer, and the input shaft cover slightly larger diameter, but with the same bolt pattern as the C model. Also there was no tailshaft behind the OD and no slip yoke. The u-joint bolted directly to the OD shaft and a double drive shaft was used with a slip yoke between the 2 driveshafts.

The gears in the different boxes had different ratios, but they were the same material, and are interchangeable between cases. In other words, the N box truck gears were not stronger, just lower ratio. These are the T85 Ford ratios, maybe GM and Mopar applications were similar or even identical.

T85 C:
Input shaft 19 teeth, countershaft 29 teeth. Input shaft is 1" diameter and can either be coarse or fine spline.
3rd gear is straight through, or 1 to 1 ratio
2nd = 26 teeth, countershaft = 25 teeth, ratio is 1.59 to 1
1st = 31, countershaft = 19, ratio is 2.49 to 1
OD = .72 to 1
So, in regular drive with OD locked out the ratios are 2.49, 1.59, and 1.00
In OD, the ratios are 1.79, 1.14, and .72
If you split shift it into a 6 speed it is 2.49, 1.79, 1.59, 1.14, 1.00, and .72. OD 2nd and regular 3rd are very close when you split.

Input shaft = 17 teeth, countershaft = 31 teeth. Input shaft is 1 1/16" diameter and is coarse spline only. It is about 7/16" longer than C. There is also a very, very rare N model with the huge 1 3/8" spline usually found behind a 65 truck with a 292 Y block engine. It can be shortened for use behind an FE.

3rd gear is straight through, or 1 to 1 ratio
2nd = 25, countershaft = 26 ( opposite of C gears) ratio is 1.75 to 1
1st = same as C box
OD = same as C box
So, in regular drive the ratios are 2.98, 1.75, and 1.00
In OD ratios are 2.15, 1.26, and .72
6 speed split is 2.98, 2.15, 1.75, 1.26, 1.00, and .72 The N trans spilts better because the ratios are noticeably farther apart. 1st gear is much lower for better power multiplication.

It is extremely rare to find a Ford/Merc T85C that does not have an overdrive. The non OD box has different ratios, 2.36, 1.54, and 1.00

This transmission has synchromesh in 2nd and 3rd, but NOT in 1st. In other words, 2nd and 3rd are in constant mesh and have a collar and snychro assembly that slides back and forth to lock up and shift into 2nd and 3rd. But in 1st the ENTIRE GEAR slides in and out of mesh between 1st, neutral, and reverse. It is a very thick and strong gear, and I have done some 5000 rpm hole shots with a 560 horse 427 in a 4200 lb Galaxie. But you can destroy it in 3 different ways;
1. Because it is not synchro you can grind the teeth down or chip them by trying to downshift into 1st while still rolling. You must come to almost a complete stop to downshift into 1st unless you know how to double clutch.
2. If your clutch is out of adjustment you can grind and chip the teeth by forcing it into 1st from neutral at a stop.
3. If your floorshift conversion linkage is not adjusted properly, and it does not move the gear ALL THE WAY in to mesh, it will only catch on the edge and break teeth off.

The Borg Warner T10 4 speed is a T85 3 speed with an extra gear, and reverse moved into the tailshaft. The cases are the same. In fact the early T89 3 speed trans ( straight cut teeth and lower 1st gear) is the same case also. This is why the shift covers on all 3 transmissions say "T89" on them. I used a T10 4 speed kit to rebuild my T85. It had everything I needed, and with parts left over.

The OD was meant to be an automatic 4th gear on a standard 3 speed. It is essentially the same as having a 2 speed Fordomatic in the tailshaft, but it is shifted with an electric solenoid instead of hydraulic pressure. When hooked up in a stock mode, it has a kickdown switch on the firewall to drop it it out of OD for passing when you push the pedal to the floor. It also has a governor that drops it out of OD when you get below 18-20 mph. With the cable pulled out it is locked out of OD. With the cable pushed in it drops into OD when you let off the throttle.


If you eliminate or bypass the kickdown and governor you can use OD in all gears (except reverse) to make a 6 speed. Just run a 14 guage wire from the hot pole on the back of the ignition switch to a pull on/push off switch mounted to the shift lever. Be sure to put a 10 amp fuse in line somewhere between. Then run a wire from the other side of the on/off switch to the blue/green wire on the solenoid. DO NOT connect it to the orange wire. This wire is for the governor on the tailshaft. Either tape it off or connect it to the governor if you want to use one. I don't use it. Also make sure that your solenoid says 12 volts on it and not 6 volts.

Some things to remember when you are using a switch to work the solenoid rather than having it automatic:
1. You have to click the switch on BEFORE you let off the throttle. The rpms have to drop so that it can "fall" into OD. If you let off before you switch, it goes to an idle and misses overdrive and "freewheels". Then you have to rev it a bit so it can fall back and catch OD.
2. If your OD is unlocked for use (cable handle pushed in) NEVER shift to reverse with the switch on. OD only works going forward, so if you shift to reverse with the switch on it is trying to go both ways at once and will lock up. You might get 2 or 3 feet, but I guarantee it will lock up, and then you will be under the car banging the shift lever out of reverse.
3. If you are going to race or smoke the tires from a stop, ALWAYS lock the OD out (cable handle out). If you don't, then all of the torque is absorbed by the sprag clutch. This is the device that lets the car freewheel so the rpms can drop into OD. It is an "overriding", or one way clutch that is made up of 12 rollers that roll up ramps and then wedge themselves into the inside of a drum. If you do enough racing without locking this out, you will eventually smash the rollers into the drum and strip everything out .
4. With this setup you have 3 transmissions.
A. With OD LOCKED OUT and switch off it is a regular 3 speed.
B. With OD UNLOCKED and the switch left ON, you have a high range 3 speed.
C. With OD UNLOCKED and toggling the switch on and off you can split into 6 speeds. It splits like an old semi before the Road Ranger transmission. Unlock OD, switch off, let out the clutch in 1st and begin rolling. You can pull the switch on at any time, but it won't shift until you let off the pedal. It's designed that way. So anyway, let off the pedal and you will feel it drop into 1st OD. Accelerate again and turn the switch off at any time. It won't drop out of OD until you let off the pedal. Then shift to second. You don't need the clutch because it's already freewheeling. Accelerate again in regular 2nd, pull the switch on at any time, let up on the pedal whenever you are ready and it will dump into 2nd OD. Same thing for 3rd. It sounds complicated, but when you do it a few times you will see how easy it is. Also it's great not to have to use the clutch.

When shifting down to slow the car it's best to have it in OD because you have compression to slow you down. If you down shift not in OD (switch off, OD unlocked) it is freewheeling or coasting in neutral. On the highway for passing I just switch off, let it fall into regular 3rd, accelerate and pass, then switch on and let off to dump back into OD. Again, without the clutch.

If you have a C model it will bolt in to any standard trans bell housing through 64. It's easiest to keep this trans and bell together, and you can use the '65 and up starter. But you can also use a C with a later housing if you drill and tap the housing for the smaller bolt pattern using the trans as a template to mark the holes. If you use the C5TA truck bell you also have to buy or make a pilot bushing that is 7/16" longer to make up for the shorter input shaft. You also have to bolt on the larger diameter later model input shaft cover, or have a shop weld and machine a collar for the smaller one.

If you have an N model it's easier to use it with the later correct bell housing. But you could have the input shaft cut shorter and it would bolt right up to the earlier housing because it has both bolt patterns. You would also need to use the earlier smaller diameter input shat cover or have the big one machined down. If you are using the big 1 3/8” input you can either weld a ring on the input cover to make it fit the bigger hole, or you can use a big shaft cover from a big shaft Ford top loader 4 speed from 65 and up. It’s the same.

Also remember that you can put either set of gears in either box.

Remember the N box OD has no tailshaft or slip yoke. If you use it in a car you have to make a "backwards" driveshaft. You get parts from a dual driveshaft truck. Bolt the u-joint with the slip yoke to the differential. Get the spline for the yoke welded to your new driveshaft. Bolt what used to be the "rear" u-joint on your driveshaft to the back of the OD case.

You can put a car OD on the N transmission so you don't have to make a backwards driveshaft. If you use a 56 and earlier OD there are 2 modifications you need to make:
1. Exchange the truck 1st/reverse shifter fork in the trans with the car one. The cams that knock the OD rod out for reverse shift are different.
2. Drill a new hole for the car OD reverse rod in the back of the N case. The gasket has both holes in it, so you can use it as a template to drill out the blank.
3. You must use the adapter or intermediate plate from the car OD, not the truck OD.

If you know the OD is working don't mess with it. If you have never taken one apart it will make you crazy. You definitely need a copy of an old manual that also has an exploded view. They are available on line for about $15. Things have to be taken apart and put back in a certain sequence. Also there are some things that can be put in backwards and it will go together but will not work. You need good snap ring pliers.

The sprag clutch or barrel cage as it is sometimes called has counterwound centering springs. One always goes on easy, but the other has to go over the top the opposite way and it is very difficult to get it on. Also,they are directional! Avoid having these springs come off when you disassemble. It is also very difficult to keep the rollers in the cage when reassembling, even with heavy grease. I always put a rubber band around them to hold them and when it is assembled it just pushes the rubber band off the end. It later dissolves.

When you remove the OD unit it’s best to knock out the plug on top and then expand the internal snap ring so the case will slide off. It can be done without this and removed as a unit, but all of the rollers fall out.

If you are converting to a floor shift, it is a tight fit but it works. Ford offered this as an option. You have to get good linkage, Hurst if possible. Hurst still makes the Mastershift but the best by far is the Hurst Dual Pattern with Synchro Loc. They come up on E Bay from time to time. You need to mock it up on the shop floor to make sure that it is precisely adjusted so you don't destroy 1st gear. If you don't have a console just cut a hole in the floor where it needs to be. But if you have an XL console with the proper floor shift cover plate, the shifter handle will not come out in the right place. You have to do some measuring and heating and bending and also lengthen the floor hole to the rear a few inches. What I did was cut the Hurst handle off near the shift mechanism, welded a flat plate on to the stub, then drilled it to accept a Ford 4 speed handle. But the handle still has to be heated and bent. Of course the reverse lockout mechanism doesn't work. The Hurst linkage will fit the 57 and up OD without modification. On the 56 and earlier the rods need to be bent to clear the solenoid which is in a different place.

When you mount the OD lockout cable you have to be sure that the cable allows the lever to go ALL THE WAY through it’s travel when pushed in or it will not let the OD engage. Even 1/16" off will cause it not to work. I don't know why. Also the end of the cable housing has to be stabilized at the end near the OD lever. They came with some sort of a clip that snapped over the end of the cable and then fastened under a shift cover bolt. If you don't have one you have to make something similar.


The advantage to an OD is that you can have a low ratio for drag racing but OD for fuel mileage. Even with 4.11s the final ratio in OD is 2.95. The highest speed ratio Ford recommended behind an FE with OD was 3.50. The final ratio with this is 2.52, which is about 1900 rpm at 60 mph, with about a 26" diameter tire. Major gas mileage.


If you have the wiring harness, kickdown switch, and the fuse/relay box that is used in the stock application, then OD is an automatic 4th gear. You can push the locking handle in at any time and the OD is ready. Simply accelerate, let off the throttle and it will drop into OD. When you want extra power to accelerate or pass a car, push the throttle to the floor and it will drop out of OD. When you let off it will shift back into OD. Come to a stop to lock OD out (pull handle out).

Also, when your speed falls below about 16-20 mph, depending upon rear end ratio and tire size, a centrifugal governor on the tail shaft opens some contact points which kills the circuit and the OD disengages so the engine won’t lug. When you get above that speed it will shift back into OD again.

The circuitry is fairly complicated and if you have to wire one you MUST have a schematic. The kickdown de-energizes the solenoid, but the solenoid will not disengage until ALL pressure is off of it. It is designed that way. So when you push the throttle all the way down and the solenoid de-energizes, a relay also kills the ignition for a tiny fraction of a second so that pressure is off the solenoid and the OD can release, and then the relay instantly turns the ignition back on again. The Borg Warner OD manual that I mentioned earlier (about $15 on line) has a blow up of the OD, a rebuild sequence, a great troubleshooting guide, and a very good wiring schematic on page 7.
Best regards

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Re: T85 R/11 Borg warner 3 speed OD Manual Trans.

Post by Theo » Fri 2. May 2014, 12:06

Best regards

Howie 1946
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Re: T85 R/11 Borg warner 3 speed OD Manual Trans.

Post by Howie 1946 » Fri 8. Sep 2017, 08:43

I have a T85 R/11 in a 57 Thunderbird that shifts into overdrive as it should but when it drops out of overdrive at about 25 mph if I accelerate it is like the engine is totally disconnected from the rear axle. This car was last driven in 1970. I rebuilt the engine and am now in the process of getting everything to work. It drives fine with the O/D locked out. I am thinking that the overrunning clutch is gummed up from sitting 47 years. I will flush out the O/D lube and refill with new to see if that makes a difference. I have worked on a number of these over the years but this is something I have not seen before.

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