The Stovebolt Site Forums The Shop Area Driveline 7-Bolt Saginaw 4-Speed with a Borg-Warner Overdrive Info Needed

I picked up a Borg-Warner Overdrive Unit to be installed in a 7-Bolt Saginaw 4-Speed Trans for my '72 C-10. I'm still in the learning process and have a couple of questions to get started on it.

One would be the Electrics. Can they be eliminated or partially eliminated for it to be used more manually? I really don't need it to work as fancy as it was designed to be. As long as I can use the Trans as usual and just shift it into OD when I need it, is all I need.

Another question would be the Shifter. I have a 4-Speed Hurst. I have read in a place or two about interference. Will it need to be modified to work?

Thanks

Unless you also have the output shaft for the Saginaw that mates with the B-W overdrive unit, you've got a very expensive paperweight. It's not going to be a simple matter of installing the OD onto a run of the mill Saginaw 3 speed. There might also be a difference in the main transmission case, like there is with a SM-318 and a SM 319 Muncie. As far as cobbling up something to make the OD a manual shift, good luck. There are some very good reasons for all the electric controls, mostly to prevent damaging the OD or the transmission by accidentally having the OD engaged at the wrong time and/or speed. OD-equipped Saginaw boxes are VERY scarce, and they're priced accordingly.

I don't think I've ever heard of mating a B-W OD to a 4 speed transmission of any sort.
Jerry

Quick questions for the forum:

How many rings on the Sag input shaft?
Is the B-W OD version R10Q-1?
What is the rear axle gear ratio that you plan to use or have?

Short answers:

The electrics cannot, or shouldn't be, eliminated but they can be simplified somewhat.
There is a solenoid needed to engage the OD.
There is a governor that can be eliminated but it is very helpful to have to automatically drop out of OD (de-energize the OD solenoid).

The problem with the Hurst shifter (in AD trucks) is that the standard tail housing mount will cause the shift stick to be too far to the rear (bench seat clearance and need to make hole in the floor). A more forward shifter mount is required (may be preferred) which means the hardened steel shift rods need to be shortened. To compound the matter, your shifter mount needs clearance for the solenoid. I really can't give good advice on C-10 since I don't have one.

Jerry,

The Borg-Warner Unit is what GM installed on the Saginaw 3-Speeds from the factory. What I have "is" the scarce one. It is well known that the OD Unit can be installed on the 4-Speed with no problems.

What I have now is a 3-Speed with what I believe is a 2.85 First, but it sure seems more like a 2.54. I need to check it over to see what it really is. My Rear is what I believe is a 3.73, but there again I need to run the numbers. Either way starting off in First is too "difficult", especially for me who is used to Granny Gear Transmissions. I picked up a 2-Ring Saginaw 4-Speed with the 3.11 First which will cure my starting off problem but, of course, I still have the 1 to 1 Rear. That where the OD comes in. That will cure my other problem as I can't keep up with Interstate speeds without it feeling like the engine is going go.

I'm not sure what version the OD Unit is, but it's the one that is standard on the Saginaw 7-Bolt 3-Speeds. I'm still learning, lol.

Appreciate the replies.

By the way, great picture. That's what mine will look like once completed. Still wondering about my 4-Speed Hurst Linkage though. I have time on my side though, it's just something I'm working on for the near future.

Hmmmmm- - - -that's obviously a conversion I'd never heard of. At one time, before Patrick's went belly-up, they sold a shifter conversion that moved the handle forward to about the middle of the case of the 3 speed Saginaw trans without relocating the shifter bell cranks. If the shift linkage can be routed around the governor assembly successfully, it shouldn't be terribly difficult to fabricate something similar to operate the 4 speed shifter. It would require a couple of heim joints and a piece of thick flat stock to avoid flexing as the handle was moved through the shift pattern.
Jerry

I have been playing with BW ODs for almost 60 years. I have read over the years where an OD from a Saginaw 3 speed installed on a Saginaw 4 speed. I have a 3 speed Saginaw with OD and I have a Saginaw 4 speed. They both use the same front case, but I have never been interested enough in the swap to see what the end of the mainshaft on the 3 and 4 speed look like. I really like the BW front section much better than the Saginaw front section. Rather than making a conversion with a 4 speed I would get some 4.11 gears to keep the thing from bogging. Even a 3.90 should improve things. The best rear I ever had behind a Y-Block was a 4.27 out of a 56 Ford station wagon. Shift linkage for a 3 speed OD is difficult to make unless you get a shifter made for it. I still have a few NOS Hurst Mystery shifters that were built or OD. I think it would be a nightmare trying to work around the solenoid with a 4 speed. I would rethink the whole thing.

The first half of your paragraph is interesting, but the second half has me going the wrong way. Not sure if you read my 3rd post above, but with what I believe is 3.73's in there now, is too low as it is. The truck revs way too high at interstate speeds.

I'm still learning on the 4-Speed project, as I know I'm not the first one out there to have one, but if worse comes to worse, I'll just install it on my present 3-Speed and keep it on the column.

By the way, although I am seeking more truck member input here, there are some interesting articles out there on it in some automotive publications I have recently discovered. I post them as time allows.

When I was in college, I ran a 1958 Chevy Del Ray coupe with a 235, a 3 speed, a 3.70 rear end, and 14" tires. I had no trouble keeping up with traffic on the brand new interstate highway system, and in Tennessee, the speed limit was 75 at the time. The idea that the RPM is too high with a direct drive transmission and that setup doesn't make good nonsense.
jerry

I agree. I really need to check to code to see what I really have. I could have 4.11's under there.

I totally missed asking you which engine you have (will have) in your 72. Makes a huge difference.

It's like a seesaw, you have to find the balance that you need.
The rear axle ratio is important to to determine 1st gear launching and final drive OD.
At the same time you have to factor in the "sweet spot" for the engine's torque/RPM curve for highway speeds.
4th gear output of the Sag is 1:1.
The R10 B-W unit has a planetary gear set that fits in between the transmission and the tail shaft housing and offers a .70:1 ratio.
The R10Q-1 has a short tail housing and when bolted to the Sag 4 speed, you can reuse your drive shaft.

Very rough idea of what I'm trying to say:

3.11 X 3.73 = 11.6 (good first gear launching)
0.70 X 3.73 = 2.62 (tall final drive, probably too much for the engine)

As crenwelge mentioned, the B-W OD was used with 3.90 and 4.11 rear axles. This design was to get better gas mileage beginning back it the 1930's.

0.70 X 3.9 = 2.73
0.70 x 4.11 = 2.87

Now after all this. You can also work up a combination or rear axle ratio and tire diameter to get the equivalent of an OD unit with your stock Sag.

The attached picture, not mine, is a rough example of a shifter application.
The other picture is a Patrick's shifter (there may be a design/shifting issue with using the very short shift rods).

I just checked on it and it is an R10Q-1.

The truck is a 98% all original '72 C-10 with a 307 V-8 and a Saginaw 3-Speed on the Column. The engine has 167,000 Miles on it and still runs great.

There will be no problem finding out what the Rear has but, as I understand it, there is no way of telling what the 3-Speed Trans is without pulling it out. But I believe it almost has to be a 2.85 First Trans.

Thanks again, great pictures and info.

My next step will be checking the Rear Code.

R10Q-1 good. That means the electrical parts are 12 volts.

1972 C-10 standard was 3.73. Options were 3.07 and 4.11 (picture).

I can't prove it but it is said that the Sag 4 speed transmission is weaker than the Sag 3 speed.
A compromise to get more parts inside the same housing?
I wouldn't dwell on it unless your long range plans are to make it more of a performance truck.

Looking at 1967 C-10 specs, OD came with 4.11 rear axle and was not available for 327 and larger V8s.
In 1968, Chevrolet dropped the 283 and replaced it with the 307 V8 which has about the same HP and torque.
Judging by the info, I think it would be safe to use the R10Q-1 with 307 V8 as long as it is treated with respect.
If you get on it, it can break.

You may want to look at the cost of rebuilding the 307, Sag 4 speed and R10Q-1 compared with pre-built Chevy 350 engine and maybe TH350C.
The AD truck guys tend to rebuild the 235 even though it can cost more that a rebuilt 350.
It's a matter of have much the pocketbook can stand.

I have a little more info on how the Sag 4 with OD was created. Let me know.

I just use the truck for light use. It is not a show truck, but gets plenty of attention on the road as well as swaps meets, etc. No performance really needed. According to my transmission buddy, the 3-Ring 4-Speed is the weakest, the 2-Ring much stronger (plenty good enough for me) and I believe he said the 1-Ring is the strongest.

Appreciate the suggestions, but a TH350 would be out of the question. I've been shifting gears for 51 years straight and can't change now. Everything I own has a Clutch Pedal, lol.

Great chart, thanks.

I'll keep you posted.

There was one of the "4 speed Saganaw with a BW OD" on ebay a while back for a lot of money. I have not seen one in use, and other than reading a couple of articles and don't know anything about the conversion. I did ask a friend that has a transmission shop locally and he had not heard of them but had some serious concerns about reverse and how to accomplish the reverse lock out for the OD.
If you have a working 3 speed Saganaw/BW R10Q OD, I would install it with the electrical components and drive it. I believe you find that it meets all your requirements.
Fred

My father, who was the first man in Nashville Tennessee to work on automatic transmissions, beginning in the late 1940's, used to say "Automatic transmissions are smarter than all drivers, and most mechanics!" He was absolutely right. It's impossible to get an automatic in the wrong gear, and even the idiots who like to run full throttle in low gear will discover that there's a safety circuit built in that makes the transmission shift before the engine over-revs. A stick shift is a toy to play with- - - -use an automatic trans and cut the pockets out of your pants!

Jerry

C10-C90 Bill Use 1/2 inch cold rolled rod with 3/8 inch heim joints,bend your linkage to fit. Drill into the cold-rolled braze in 3/8 bolts or thread the hole. My Corvette has those that are 50 years old,smooth,slick,short throw. Use the electrics,I move the kickdown onto the stick,like a line lock. you could build an O.D like a brownie but its a big job. The O.D. relay is not available anymore but can duplicate in an ice-cube relay. perfect that it'll be slick,had one in 67 in a 53 3100 283 2x4 truck ran the wheels off of it !!

rfs56trk If you park the vehicle with it in reverse it will automatically be out of O.D. so it wont roll away. Either out fit (3 or 4 speed )will work great. I made one like a Brownie,it worked fine too took a welded shaft eventually built 4 of those there is still one in the barn.

buoymaker Had a 66 malibu 327-saginaw 4- speed,I certainly got on it never had trouble,was geared very well nice car and really sounded good Carter AVS 4 barrel had those red tetraethyl lead stains on it.

Sounds good. Appreciate that info.

All overdrive transmissions will hold in reverse when parked with the OD engaged. That is not the issue. The reverse lock out is designed to prevent the overdrive from engaging in reverse when driving. If you look at the overdrive shifter shaft, it has dual components, one part manually engages/disengages the planetary actuated with the cable, the other component disengages the planetary with a cam assembly on the reverse shift lever internally. The reverse shift lever on a 4 speed may not be in the correct position to perform this function.
Fred

Another question in the meantime. As we all know, the OD unit is part Mechanical and part Electrical. What would happen if one of the Electrical devices quits working while on the road? Would it effect the normal operation of the trans in any way?

Fixite7. 327 4 speed Saginaw, yes. 327 4 speed + OD Saginaw, Russian Roulette.

There was a write-up by C.J. Baker in Hot Rod April 1975. The article was titled 4+O = 8.
The article today is, How To Get Done!" (https://www.motortrend.com/how-to/get-gone-grassroots-overdrive).
Be sure to click on, "see all 25 photos" to see needed details of the machining required.

Before you begin, read the manual on how to rebuild the 3/4 speed Saginaw transmission as well as the manual for the B-W OD.
Don't be the rookie that takes one apart and has parts fall out on the floor.

Performance rebuild information here (https://www.motortrend.com/how-to/ctrp-1009-saginaw-transmission-rebuild).
Be sure to click on, "see all 31 photos" to see details.

Questions and B-W OD Troubleshooting/rebuilding:

https://fifthaveinternetgarage.blogspot.com/2017/01/borg-warner-r-10-and-r-11-overdrives.html
http://www.oldwillysforum.com/forum/TechData/BWOverdriveManual.pdf
http://devestechnet.com/Figures/bwrebuild.pdf

1. Have good or even better, great brakes.
2. Have good parking brakes and use them when parked.

Another Wiring Diagram:

https://fifthaveinternetgarage.blogspot.com/2018/12/borg-warner-r-10-overdrive-wiring.html

Alternate Wiring:

http://devestechnet.com/Figures/bwwiring.pdf

I apologize to the forum for all the previous links.
This post can generate a multitude of questions and I was hoping to make it easier by self-education.

To the best of my knowledge and research, the BW OD came in vehicles that had 4.57 rear gears as it is a 30 percent overdrive. 4.57 x 0.70 = 3.199. It is darn near a 1,000 rpm drop from 3rd gear to 3rd gear OD. I have this setup in my truck with 4.57 rear gears. I wouldn't even consider running this setup with anything numerically lower than 4.57. From what I have read the only difference between a regular 3 speed case and one modified for the BW OD is the hole for the reverse lockout rod. The tailshaft lengths are the same, the yoke is the same, it is a simple swap from one to the other, but modifying a 4 speed case and fabricating the linkage is going to be a nightmare as already stated.

Mine is not setup with the relay, kickdown switch, etc. It is a switch on the dash and the cable to engage and disengage the unit. It works great, but there is no passing gear like it would be fully setup. The way people drive nowadays there is no need to pass as they are all going much faster than an old rig can go. Cruising at 65-70 on the open road while turning 2,400-2,500 rpms is nice, though.

Appreciate all the links.

There is no such thing as too many.

That's what I'm interested in actually. Not only am I missing the carburetor parts, I would prefer it that way.

A contract instructor who worked for the Tennessee state trade school where I taught auto mechanics in the late 1980's had been an engineer with Saginaw when they developed those transmissions. They were designed for use behind the 4 cylinder Vega engines, the Pontiac Firebird OHC sixes, and other engines with low to moderate torque ratings. He claimed that in order to make them survive the torque of most V8 engines, they had to do some very special heat treating of the gears, and a lot of other upgrades. He said that he and a few other researchers went to the extra effort to beef up the individual transmissions they used in their own hotrod projects, but he was not impressed with the Saginaw 4 speed for general use with high torque engines.
Jerry

Thought you may have a "FYI" interest in the attached. I did this mod on my 3 spd OD trans. My differential gear ratio is 3:38 (1957 Chev NAPCO truck). I have no problem with pickup, but it does have a modified 348. When I had the 283, it was still decent.
don

Now that's a good question, what year was the R10Q-1 available? As not only was OD available in Saginaw 7-Bolt trucks, but a friend of mine had a '66 Chevelle Wagon with Factory OD.

The R10Q OD was available from 66 through 69. Some may have been available in 1970.

Most stock applications used a 4.10:1 differential ratio when the OD was ordered. My 56 has a 3.90:1 rear end and it works well.


Fred

Greetings. New here... I own a '71 GMC Vandura with the Saginaw SM318 three-speed and a column shifter. On a different forum, someone told me that the column shifter could shift the four forward speeds, and a PTO cable or other arrangement could be made to operate the reverse fork. This struck me as a reasonable thing to attempt. I am interested in adding the four-speed because it spreads out the gears more. While I enjoy driving the three-on-the-tree, having only three forward gears is so few...

buoymaker thought my post bombed,guess you saw it,that saginaw worked good for me with 327. That 66 malibu was the best ,just the sound of it was great. I later put that engine in a 3100 never sounded good after that,ran fine. So you live and learn.

A much simpler swap would be to install the SM 319 OD transmission and you'll have five forward speeds available, not four, and have overdrive to boot. As long as the vehicle speed is above 30 MPH or so, depending on the rear end ratio, OD can be engaged with the transmission in 2nd. gear. If you want to use 3rd. direct after that, just make the manual shift and use the kickdown switch to get 3rd. direct. I learned that trick on a 53 Nash Ambassador in the late 1950's. I was even able to use OD in 1st. gear, but getting that old Nash engine wound up enough to trip the governor in the B-W overdrive probably wasn't the best idea I ever had.
Jerry

I checked the Rear Axle Code on my '72 C-10 today.

It's an RHC which means 3.73 as figured.

Now on top of this, I put 265/75/15's on the back to help change the Ratio some.

How much trouble am I in now? lol

c10c90bill keep trying make your own.

You'll still be able to use that OD gear- - - - -but only when running on a steep downhill grade, like Wolf Creek Pass, for instance!



Jerry