The Stovebolt Site Forums The Shop Area Driveline Saginaw 3-speed Overdrive Question

Robert - After doing a bit of research and comparing your side cover shifter detent spring (1st pic) with the one pictured in an original side cover (2nd pic), your existing spring in fact looks to be the incorrect size. I searched through available Shop/Service manuals and parts books and can find only 1 spring for the Saginaw 3 speed (also fits the Saginaw 4 speed too) called for. Nothing shows a different strength/style spring for the OD equipped 3 speed.

Armed with GM# 3831718 - Spring, detent cam (3rd pic shows applications from parts book), I searched a bit on the web and actually found some NOS springs being offered. The pictured NOS springs (4th pic) are clearly much stronger, with very little hook end lengths and lots more tension coils than your existing spring. Just my $.02 worth on this, but get you one of those NOS springs and give it a try. I think it may solve your popping out of reverse dilemma.

PS: I posted the links to a couple of NOS spring ads in your Truck Parts Wanted ad.

Thank you, Dan, for taking the time to do your research. I agree. The photo of the spring in my friend's side cover looks more like the offerings that you located than it does the spring in both my OD trans and in my straight drive version. I ordered the green box one that you show above. I will post how it works for me.

Again, thank you for your help!

Side note: I had a trip scheduled for last August, so I put my truck on blocks and ran the fuel out of the carburetor. Events occurred, so the truck is stuck in its current state for into the near future. Turning a negative into a positive I have been working on a long list of "maybe, someday" repairs, modifications and fixes, the biggest of those being getting a disc brake conversion working to my liking and getting this OD transmission working. I look forward to all of my changes being finished and working properly.

Glad it may help and looking forward to a future report on the OD issue. Understood about how "life happens". Working on those other things still qualifies as working on the truck!

I received and installed the new spring for the side cover. The new spring looks like the spring shown my friend's side plate in the photo above. The photo below shows the spring that was in the side cover that came with my OD transmission, the spring that is in my straight drive version side cover and this new spring. The smaller springs measure 0.048" thick. The new one measures 0.063".

This stronger spring does overpower the spring in the lockout pin, so the shifter does hold in reverse without having to lockout the OD first. This stronger spring makes all three gears harder to engage.

I'm almost out of excuses to keep this truck on blocks. I'll update again after I make a test drive.

Robert - Sounds like Great News my friend!!! Looking forward to test drive results!

I made some test drives. I am happy with what I have. The OD works well. I can hear the solenoid click, so that tells me when it is ready to engage overdrive. For my 3.73 differential that click occurs around 30-35 mph. My first couple of shifts to 3rd occurred at the same speed that engaged the overdrive, so those shifts were from 2nd straight to 3rd OD, and the truck speed was too slow for 3rd OD. What I migrated into is allowing it to go from 2nd straight into 2nd OD then continuing in 2nd OD until I'm ready to shift to 3rd OD. I find the automatic upshift to not be as seamless as I expected from reading the manuals. I have faster and smoother result by pushing in the clutch to allow the engagement.

I'm not yet sure about the kickdown operation. Of my 4 attempts, by flooring the accelerator, only one kicked into 3rd straight.

All is not finished yet. After my failed kickdown attempts the overdrive no longer engages. I tested the solenoid; it does engage during testing. I will later move through the rest of the tests and update when I find out what is wrong.

Thank you to everyone who offered advice for this project!

Glad you made some progress Robert. Keep at it my friend - you will get there.

I replaced the 20 amp fuse and took another test drive. At the OD engagement speed I heard a click, but the OD did not engage. I learned in my step 2 test below that there are actually two clicks: one for the solenoid starting to engage followed immediately by another click for the 20 amp fuse popping.

I'm working through the troubleshooting tests. I am following a combination of the checks in an original Borg Warner manual and in a Ford OD manual. The BW manual is for 6V positive ground systems, so I worry about doing something backwards from that instruction. I chose a Ford relay and kickdown switch, so I'm more following the Ford manual. I can follow when it shows to make this test at this terminal, but I cannot follow so well when the test is to do something with a particular color of wire. My colors are different.

What I have so far:

1. The solenoid does work when I connect it directly to the positive battery terminal.
2. I power the OD system through a 20 amp fuse from my ignition circuit. Grounding the governor immediately pops this fuse.
3. The relay does receive 12V per a test light.
4. The 10 amp fuse on the relay checks good.
5. A test light on the solenoid terminal of the relay should, per the Ford manual, light the test light, and there should be heard a click from within the relay. That does not happen in my test.

I'm not yet clear on how to check the kickdown switch, so I've not yet made that check.

Does anyone have advice for me?

Thanks!

It sure sounds like you have an overload of the 20A fuse in the solenoid circuit. It's possible that the solenoid coil is internally shorted and draws more current than it should. Do you know what the resistance of the solenoid coil should be? Measure that with an ohmmeter. Or possibly if the solenoid was designed for 6V, the 12V is making it draw enough more current to blow the fuse.

When you connect the solenoid to the positive battery terminal, is there a fuse in the circuit? If not, and no smoke comes from the solenoid when you do that, you should connect an ammeter in the circuit and see how many amps it draws when you connect to the battery. Dollars to donuts, that's going to be more than 20 amps. But don't just stick a higher amperage fuse in place of the 20 amp one, or you may burn up something more valuable than fuses.

Thank you for your advice! I do not remember how I chose 20 amps for the main feed, but I do agree with you that I do not want to put a bigger one in without knowing that to be the problem. When I took my first test drive I got near 45 minutes of use with no problem other than me learning how to drive it, so it seems like everything was correct at that time.

When I tried the kick down feature it did not work 3 times. It did work on the 4th try, but the overdrive stopped working at that time. Since then it pops the fuse immediately upon activating the solenoid.

I use a plain jumper wire to test the solenoid. It seems to be okay with that. It works without smoking. The fuse pops when I ground the governor. Something is wrong there. I do not know what to think of the relay test not giving the result described in the Ford manual. I have not yet figured out what to check on the kickdown switch.

I am confident of the solenoid being 12V based on my checks working and presumably having been in use by the previous owner.

Again, thanks!

IDK, after all that , I`m glad mine has a manual OD. After 45mph ,I just pull the cable out.

I can see the advantage of that, BD, but I like the doodadery of this setup, so I'll have fun when I get it working.

Thank you to Fred/rfs56trk for suggesting and telling me how to bypass and disconnect the kickdown switch. I did that. My under the truck check of grounding the governor did make the solenoid work, but for my test drive the very first engagement popped the fuse again.

The research will continue. Next I will look at why my relay test did not go as described in the manual.

It is fixed!

My version of following Fred/rfs56trk's instruction above to bypass and disconnect the kickdown switch was to use one of the screws on the kickdown switch to connect the two wires that needed to remain connected together. He followed up by alerting me that a short in that switch still had access to the system, so I separated the pair from the switch. Now the overdrive works as it should.

Thank you to everyone who gave advice!

I'm having great fun driving my truck around and playing with my new toy. I do, however, keep in mind that I do need to buy another kickdown switch and get that working before I am completely finished with this project. I am shocked (shocked!) that an aftermarket reproduction switch failed on its first use.

The next one may or may not come from a different vendor. I recognize that probably all vendors source from the same factory, but buying 2 or 3 duds to get one that works is better than getting nothing at all.

Multiple forums make multiple mention about it being a good idea to make the truck stop better before you make it go faster. I 100% agree with that and started a disc brake conversion in August, 2023. I had many problems with that and have been working on it since then. I finished the fixes while I was fixing this transmission, and I find that the brakes are wonderful now. Sure, quick stops, light pressure, plenty of pedal remaining for use in emergency. I'm having fun enjoying that also.

Woohoo!!!

So glad to hear of your success and that folks have been able to help out along the way.

Now then - When are we going to get to see some pictures of the truck??? You've posted parts pics, so you have the skills. Inquiring minds want to see - LOL!!!

Give Robert some time Dan. He's only had this truck since the '70s.

I'm honored. Thank you! Here are a few photos. The 1st one is from 2013. I've not been able to get a better photo since then. The truck still looks like that. The 2nd one was taken a few months after I finished putting it together and getting it registered. Based on my clothes and the stickers, I put the photo in the first few months of 1979. The 3rd photo is of the engine. The 4th and 5th photos are in progress photos of this overdrive transmission installed. They do not include the cable or the wiring.

Do you still have those original wheels and hubcaps?

Robert - Thanks for gracing us with pics of your truck. Such a long time labor of love. I really enjoyed the very early picture. Reminded that I once had hair like that - LOL! Glad you are still at this and looking forward to future sharing!

I don't get on this site very often any more so I haven't been following your thread. I guess you do have it wired correctly. I think I gave you a wiring diagram. I have one in my photos so I will post it. The kick down switches all do the same thing. They interrupt the ignition while the solenoid is shifting the planetary. I have used one out of a later model blue oval. They can be surface mounted instead of drilling a hole in the floor. It is a part no. C0AF-7A652A. The blue oval used 12 volt negative ground in 1956 and later. 1955 blue oval used 6V positive like GMC. I am assuming you are running 12V negative. I don't think I ever blew one of the 20 amp fuses. The 1956 blue oval used a pretty neat relay with a 20 amp fuse on it. It is a B6A-6915-A The solenoid on the Saginaw fits a Saginaw only. Blue oval applications used a different solenoid. Electrically they do the same thing, but the shaft is different. Kathy and I are in a hotel so all I have access to is what I have in Google photos. I don't remember which one is which. But they don't interchange. I like your shift levers. I am thinking of something like that for my roadster. The backwards shift pattern is awkward. I am thinking of using belcranks to reverse things. I did find the key for it shortly after you left.

It is good to hear from you, Kenneth. I do have the documentation that you gave me. I did buy the Ford version of a relay and a kickdown switch. It is aftermarket, so I cannot match the number, but it is a nice little box with a 20 amp fuse. Another forum member provided me a harness and a diagram to wire the Ford parts to my GM setup.

After having been advised by member rfs56trk on how to bypass the kickdown switch when my OD stopped working it began working but then worked for only a very short time. Back onto the blocks. This time the solenoid did not work during testing. Member rfs56trk offered further advice on how to disassemble the solenoid then give it a cleaning and a check. It passed the bench test today and is reinstalled, waiting for the next test drive.

I got my test drive in. Again, the fuse popped at first solenoid engagement, so it never engaged. Back on the ramps with the solenoid still installed I applied a jumper from the pos battery terminal to the #4 solenoid terminal. The jumper acted like it wanted to weld itself to the terminal. I repeated that test with the harness removed from the #4 terminal then again with the harness also removed from the #6 terminal. Both times the jumper acted like it wanted to weld itself to the terminal. That makes me think that I developed a short in the solenoid somehow.

Below is shown a sketch that was provided with the harness that I used and the sketch that member Crenwelge provided with the connections matched to the sketch for the harness.

Member rfs56trk has an idea that I may be able to make a certain Ford solenoid into a solenoid that will fit and work for this GM transmission. I will explore this option further.

I bought an NOS kickdown switch to replace the reproduction one that I had to bypass. Below is a sketch of my side by side continuity checks. I found the two lower terminals do not have continuity on the reproduction switch, which would make the solenoid not engage. I do have continuity for those two terminals on the NOS switch.

The GM instruction shows to set plunger movement at 0.18 inches. That is what I did. I do not find a measurement in the Ford instruction. It seems reasonable to me that with the Ford switch being designed for under floor use the plunger should be able to be pushed all the way into its sleeve without bottoming out. That does seem to be the case for both the reproduction and the NOS switch.

I did not find anything in my checks of these switches that would cause an electrical short.

Member rfs56trk/Fred has an idea that I may be able to make a certain Ford solenoid into a solenoid that will fit and work for this GM transmission. I find that his idea does work. The Saginaw version of the Chevrolet overdrive transmission uses a solenoid that is made by Warner. Fred told me that the Ford solenoid is internally the same. I found that the plungers are interchangeable, so I installed the long plunger from the GM transmission into the Ford solenoid. There is one external difference. The diameter of the step in the mounting flange is bigger on the Ford version. The height is the same on both solenoids. I found that diameter on the GM solenoid to be 0.765". I found that diameter on the Ford solenoid to be 0.823". I machined that diameter on the Ford version to 0.765".

I have the NOS kickdown switch and this modified solenoid installed. The system passes the checks that are shown in the Ford overdrive manual.

We are forecast for rain/sleet/snow for the rest of this week. I do not drive this truck on wet days, so I will make a test drive next week. Below are the sketches of the measurements that I made.

Edit: I'm told that the solenoid that I used is not unique to Ford. I believe that any solenoid from that era that was made by Borg Warner (RBW) may work for this modification.

Robert, have you read thru the Service Manual for the overdrive transmission? It has some troubleshooting steps, and an explanation on how it's supposed to work, as well as some adjustments of the relay, which might be part of your problem with the fuses blowing. The solenoid has a pull-in winding and a hold-in winding with internal switches. If those are not working correctly it could cause high current for long enough to blow the fuse. Here's the section on the Overdrive Transmission from the 55.2 Truck Service Manual.
Hope that helps. The circuiting is a little complicated to figure out without some explanation, which the manual has.

I like it. Thank you! If I figure out how to print it, then I will. I have not seen this manual before.

You should be able to take a screen shot of each page and save it to a PDF or JPEG file, then print those.

Done! Again, thank you! It took me some time to figure out that the pages that are not shown in the index can be found with a 'next' option on the pages that are shown. It is easier for me to read pages than screens. This manual seems to me to have more information than the Borg Warner and the Ford manuals that I have.

Good deal!
I happen to have an original Truck Shop Manual for 1955 2nd Series and it had the info I posted, but trying to take photos of a fairly fragile old manual wasn't going to happen. Keith Hardy's website has done the work for us, although like you say, reading on the screen is a bit difficult. Keeping or getting the grease off the keyboard is tricky, too.

Yes. I have the pages on my bench. Again, thank you!

I'm making more checks before I test drive next week. I'm unnerved that a continuity check with a meter shows continuity between 3 of the 4 terminals of the kickdown switch (those for the distributor, the governor, and the KD terminal of the relay but not the one for the solenoid) and also for ground and all 3 terminals of the relay. Removing the fuse from the relay shows continuity at only the distributor terminal of the kickdown switch, the ignition and solenoid terminals on the relay, and ground. The check is the same with the ignition key turned on or off.

This puzzles me. I do not think that I should read continuity between the ignition hot lead and ground. But then I find on page 7-31 of my newly printed repair manual pages that the first check is to "ground the KD terminal of the solenoid relay with a jumper lead. If the solenoid clicks, the relay and solenoid circuits are in operating condition." I make that check, and the solenoid clicks, so what I have could be good.

So I don't know if I am unnecessarily overthinking this or if something is wrong. I'll find out next week.

I thought it was weird that your repro and NOS kickdown switches were different as far as continuity between the terminals closest to the plunger end. But I hadn't dug into it. From looking at the wiring diagram (attached) from the Chevy manual, I believe that those two terminals should have continuity, as electrical diagrams typically show contact positions in an at rest or non-powered condition. That being said, it appears to me that your Repro switch is no good. Don't know which you are planning on using, but I'd go with the NOS.

Yes, thank you! Member rfs56trk/Fred identified that problem for me. The NOS switch is the one that is installed and wired. The check that I made today with the 1955 GM instruction and the check that I made earlier with the Ford instruction both show that what I have should work. I don't like what I find with my continuity checks, but I don't rule out operator error. I'll find out next week.

Robert - Not sure if it may be of any help, but I've attached a PDF with a scan of a 1955 Passenger Car FAM wiring diagram for the 3 speed OD set up as well as a blown up version of the diagram in the 1955.2 Truck Shop manual, just in case they prove of some added help with your project. Looking forward to seeing how the next testing turns out.

Thank you, Dan. I added that to my notes. I made some test light checks today. I think I am just confusing myself. The fuse is not popping, and the solenoid and the relay click when testing shows they should, so I will do nothing more before my test drive.

I got a nice test drive in yesterday, 50 miles out then 50 miles back. I had to readjust the kickdown switch height after an earlier test drive, but the whole system worked well yesterday. It is a fun toy, and I am very happy with it. With my 3.73 differential I find that I want to lock the overdrive out when driving on 35 mph roads and on 45 mph roads going just stoplight to stoplight. I leave it ready to engage on 55 mph and up roads. The solenoid engages before I like to shift into 3rd gear. Sometimes I let the overdrive engage while in 2nd then run 2nd OD until I want to shift to 3rd OD. Sometimes I shift early into 3rd then run that until I want to let the overdrive engage. I have not yet chosen which one I like better.

Thank you to everyone who offered help and advice. It looks like my original solenoid was sometimes working and sometimes shorting. Fred's fix, noted above, took care of that problem.

Since last Fall I have been driving only short drives while I was working on this overdrive project and also getting my front disc brake conversion to work as it should. I had noticed the truck running a little rougher than I am used to. An added bonus for me is that somewhere during its 100 mile drive at 60ish mph that cleared up, and it is back to running perfectly smoothly.

The Saginaw transmission, with its synchronized 1st. gear, plus the OD means you've got the equivalent of a 5 speed. You don't have to come to a full stop before engaging 1st.gear when approaching a stop, then you have 2nd., 2nd OD, 3rd., and 3rd OD available. That's as good as, or maybe better than running a T-5, at least in my opinion.
Jerry

It's a fun toy. I did not want to give up my column shift, so, as you noted, I have five gears to play with. And I have the different ways to engage them that I can play with.

Outstanding to hear the positive outcome and results of you’re efforts! Maybe one of these days you will post some picks of your truck out and about in the Who uses their truck as a truck thread in GTT?

I'm glad to hear you finally got the thing to working. I always keep OD transmissions locked out around town. And of course I did second over at times just for the right gear. I think back in the day I would have rather had a T-5 if they had been invented then. But they came out about 15 to 20 years too late for me to enjoy them. 60 years ago our main street had black marks like a runway. And I put quite a few of them thee. Shifting from 1st or 2nd direct to over was just too slow. And my Y-Blocks really didn't need that extra gear. I used a Hurst Mystery shifter and it was much faster than waiting for the OD to shift. Of course this cost me quite a few input shafts and cluster gears. I still have some spare sets that I will probably never use.