3 on tree with OD, How do you shift it!!!!!

[steveo3318]

Ok I am contemplating getting 7 bolt saginaw 3 speed for my 67 with O/D. I am not changing to a auto so please don't suggest it. I love my three on the tree but just want the O/D.

I have done a ton of research and understand how it works. But I have yet to find any good literature on how to drive or use it. can someone give me a step by step process of how to drive with it. I really only intend to use it in third at highway speeds. My main questions are when do you pull the T handle, does it have to be pushed in when stopping, can you really shift with out using the clutch when its engaged. Again a simple step by step from someone that's driven one would immensely help. I just don't want to tear it up

[19673ontree]

I love the 3 on the tree shifters also ! All a overdrive saginaw 3spd is , is an overdrive unit that is engaged with and electric solenoid , if its in overdrive you have 3 high gears if its out of overdrive you have 3 low gears , if you wanted to you could hook it up on a toggle switch and use it any way you want , I put a 3.08 in my 67 which worked out great ,, good luck with it ,,,

[steveo3318]

What engine do you have and what kind of rpms are you running around 70. I jus don't want the truck to be screaming on road trips to the beach this summer

[Andy4639]

My 67 have the 283 with over drive.
If I remember right when the handle was pushed in it was in over drive and in 3rd gear you would let off the gas pedal and then back on it and it would kick into overdrive. Didn't have to pull and push the brake lever for stopping. Just put it where you wanted it and drive it.

[19673ontree]

Ive got a 250 six cylinder and a saginaw 3spd before I had a 3.73 the hood would have blown off at 70 LOL now with tbe 3.08 im taching 2500 or so at 70 a friend of mine said today he has a saginaw 3 spd with overdrive he is gonna take out and sell so I will put it in my truck id say that will bring my rpms way down !

[Andy4639]

The old factory OD that I had was vacuum operated with a selonoid on the carb. It would knock a couple of hundred off the RPM's is all if I remember correctly.

[SS Tim]

Right from the 68 driver's handbook.
Pulling the handle out disengages the O/D function making it like any other 3OTT trans, provided it is properly installed and working. The stock rear gears were 4.10s with the O/D.

[In The Ten Ring]

I REALLY need this.

[19673ontree]

Hopefully I will have one soon !

[steveo3318]

Thank u ss Tim. That's exactly what I needed to see. I am a big road trip cruiser so I am thinking a set of 308s and the OD may be my best bet. Does anyone know what a factory 67 with v8 and three on the tree 1/2 ton swb may of came with gear ratio wise from the factory?

[twouvakind]

Momentarily floor the floor the accelerator while fumbling with a handle, that's interesting.

[SS Tim]

Originally Posted by steveo3318

Thank u ss Tim. That's exactly what I needed to see. I am a big road trip cruiser so I am thinking a set of 308s and the OD may be my best bet. Does anyone know what a factory 67 with v8 and three on the tree 1/2 ton swb may of came with gear ratio wise from the factory?

Glad that was what you were looking for.

But I seriously question using an O/D with 3.08 gears.
That works out to an effective ratio of 2.15 in O/D.
Like I said earlier the factory ran 4.11 which bumped to 2.87.

Your truck probably has 3.73 gears which bump to 2.61 and I doubt you would want to go higher.

Seems like everyone is jumping on this as a great idea, but you need to remember Chevy only used the M10 in the lightest of applications, generally excluding all 327, 350 and 396 engines. While some have had success and even gone as far as adapting the O/D to a Saginaw four speed it is not strong or parts supported.

The solenoids and relays are important system components and it is designed to be used as a system. To address the electrical parts and expense of keeping these going there have been over the years aftermarket adaptive controls. These manually operate them mechanically. It is also possible as stated above to manually control the electrics with switches. But that does not easily address the kickdown function for passing or urgent accelleration needs, there are limits.

The O/D section is not designed to take torque multiplication in gears lower than high nor a hopped up engine.
A big reason these were not popular is the fact that they overrun or coast on deceleration unlike a modern O/D trans, that through direct gearing, sees engine braking. These just spin like a one-speed coaster bike.

Finally do you want to be cruising a long way from home with an orphan trans with poor and specialized parts needs.

There are better ways and a Gear Vendors unit makes a lot more sense. The problem is it would have to be a carrier bearing replacement installation. However installed in conjunction with a HD 3 speed from a BB or 4x4 truck, it would make a great column shift combo (looked into this for a C20 Longhorn).

For what it is worth I played around with a saginaw four-speed plus O/D section for my 72 L79 Vega panel truck. Even in the very early eighties it was hard to find parts for the O/D to get mine to new servicable condition.

[SS Tim]

While we are here, in your research have you looked at the factory service and overhaul manuals?
http://67-72chevytrucks.com/vboard/s...d.php?t=558016

[steveo3318]

Thanks for all that info and you bring up some great points. One of the best ones is do I want to be stuck 200 miles from home if I want to bark 2nd in front of some kids which I am likely to do. You have made me second guess the whole thing after looking for parts for one all afternoon lol.. Also the Gear Vendors has some extremely nice stuff that I might not mind dropping the coin on, the only problem is they don't support any 3 speed manuals. Only 4 speeds,5, and 6. Unless I am missing something. Can you give me any info on a gear vendor unit on a three speed if you have ever seen one. Thanks so much and I may just end up with 308's

[SS Tim]

Good it seems you took a pause and reflected, that is a good way to plan modifications.

The Gear Vendors unit you would need is the inline unit that mounts like a divorced t-case or a carrier bearing. These are not listed as a general application but more of a universal/unique situation solution.

If you look the Ford ZF manual applications you can get an idea.

Overall it looks like a great but pricey solution and the shiftless gear changes would be great going up through the gears.

The price point is high new but used units are out there.
There are also other Laycock based units like Gear Vendors that people sell too. Many are the Volvo units (sometimes AMC) and might actually work out for your application.

But you want to be careful about buying an unsupported unit like a DNE off a 4+3 'vette application or even a USA Gears inline overdrive. Hone overdrives can occasionally be found but then you are back to a big parts problem.

Another thought is the Ranger overdrive from Advanced Adapters. Should be adaptable to you three speed. http://www.advanceadapters.com/categ...lete-units/91/
It mounts in front of your existing trans between it and the bellhousing. So with any gear you can select High or Low. Don't remember what the ratios are but I think it is a little less than the .70 the M10 offered.
There may be drawbacks like extending the column shift linkage and deciding on if you can live with a floor lever for the GO gear. Might also need to go to the high hump floor cover to provide enough room. Hey just thinking out load here.
There is a very good real world write up on a _ _ _ _ here.
http://www.fordification.com/tech/torque-splitter.htm

[WIDESIDE72]

On a related note, I have an overdrive in my 55 chevy second series pickup. We pulled it out of a truck in a wrecking yard nearly 30 years ago. I believe it was a 58 or 59. It appears to me that the overdrive bolts onto the back of the stock 3 speed trans. Funny thing is I only noticed the trans because the chassis was sitting there with no body and i saw that the trans looked different and wondered what it was. My older brother told me and when i asked the yard owner, he said he would take $50 for it. Since the body was gone, i didnt get any of the supporting parts to make it work as originally intended, but my brother drove the truck for a while with it. Iirc, you could get under the truck and put it in od or take it out. I think in this set up it overdrove every gear (?) as i remember him saying you had to slip the clutch a little to get going. (The truck still has the original rear axle which i believe has 4.10 gears.) Probably not the best idea, but we were just kids!

I would like to find all of the additional parts to make it work as originally installed.

[lutronjim]

I have a OD 3 speed manual tranny out of a 69 chev that I ran in my 70 PU. It needs syncros and either front bearing or needles in cluster - some noise. Has solenoid and od pull handle. I don't think I still have kickdown switch for carb.

I read that some think the od tail bolts up to regular tranny but there wrong. The tranny has a rod that prevents od in reverse. The od wont backup. In fact, you can jerry rig it as a hill holder if you force the solenoid to stay energized.

Problem would be that I am in Atlanta and the beast is very heavy.

[Don Brace]

My Longhorn has a three speed overdrive behind a 350 v8. I installed it five years ago. I drive it with out beating on it because the truck is a one ton and weighs about 4500 pounds. It has 4.11 gears and on bathe road get 16 MPG. I haul 3000 pounds of corn three times a winter. The OD was used when I got it and has never failed.
My 55 Chevy Nomad has an OD that I have driven more than 100,000 mile with no problems.
If you are going to race your truck, pull out the overdrive handle and give it hell. I do that with my Longhorn. Do not do it in overdrive. The sun and planetary gears will pop.
Don Brace MN

[lutronjim]

To shift into overdrive you have to be going faster than the lockout governor usually about 20+_ mph. You simply let your foot off the gas and it will shift into overdrive.

To shift off of overdrive you have to floor the gas petal this will cause the kick down switch to short out the coil on the points side to cut power, the solenoid will drop out by its spring, and the unit will shift into straight drive.

Of course the manual lockout has to be pushed in.

[SS Tim]

To expand a little on the above post. Anytime you floor the throttle it drops to direct drive. Pulling the defeat lever keeps it in direct. This is important for compression braking if you need it or simply parking as the unit can freewheel if left in O/D with the engine off. A well functioning park brake and its use are strongly recommended.