Inliners International Forums General Discussion Drive Train 3 speed overdrive help

Hi everyone
I have a 55 chevy three speed overdrive behind my 235 in my 54 GMC and it is running great. Only problem is I don't have the overdrive set up yet. I thought I read some where you can set up a cable for the lock out, to put it in and out of overdrive and a switch to engage it when you want to use it. Will this work or does it need to be set up with voltage regulator and kick down switch etc. I really want to use it on demand and set up as easy as possible.
Thanks Steve

Dear Steve;

Yes; it can be done that way. You would like it better the way GM made it though.

How do know the OD (mechanical) is okay??

Thanks for the reply John

I have taken the overdrive section apart and cleaned the whole thing out. It looks to be in real good shape. The person I bought the tranny from said it had been removed from a truck back in the late 50's and just sat around for all these years. It was missing the speedo gear and when I took it apart there was sand in it, mostly in the overdrive area, no wear to speak of all gears look to be in excelent shape. I have been driving this truck for the past three weeks with this tranny and it is real tight. I will set up a cable, I purchased one on ebay but to short to use. I will set up a switch and see how the overdrive works. If I like it as much as I think I am going to, then I will look at other options of setting it up. Drive train wise the only other thing i will need is to change is the rear end gears. I currently have the original 3/4 ton 4:57 would like to find the 4:10 out of the 67 to 72 3/4 ton with automatic. Then the drive train will be trully ready for any type of driving.

Thanks again
Steve

S;

You filled the OD section with oil, Right??

The rear section has It's own (oil suply) & does NOT get oiled from the "main case".

A PTO cable will work good, if you can't find an orginal.

Good luck.

www.classictruckshop.com/clubs/earlyburbs/projects/over/drive.htm Give this a try. Tab through it for wiring options... SCRAP

John and Scrap

Thanks for the info. I have been off line since about the 16th of the month. I just wanted to thank you for the replies. John yes I did put oil in the overdrive section of the tranny. I will try to set up a switch and cable this weekend and go from there.
Thanks again Steve

Hooking up a switch to turn it on and off will work, but you need to run it thru the governor so it won't engage when you are not moving. Otherwise, you will forget to shut off the switch and when you park it in reverse and back up, you will put it into first gear while you are still rolling. You will come to a sudden stop because it will not move backward if the OD is on and the trans is in a forward gear. You will end up breaking a lot of expensive OD parts. Trust me, I know this for a fact. Joe

Joe,

Thanks for the information. Does it set up with the wire going the switch to the governer then directly to the solenoid? Believe me I don't want to be messing up any parts. I want to mainly verify the overdrive is working properly and that I am going to like it. I don't really believe I won't like it. I will go with the original set up if possible or I may try going the way The Burb Club has it set up. I want to be able to have overdrive in all gears. As most of us know one step at a time to get where and the way we want our rides to be..

Thanks again Steve

Dear Steve;

Joe is correct. The solenoid MUST ground through the "governor". That protects the system; like he said.

You must shift the lever "in" to test also. That would be 'pushing' it to the rear of the tail housing.

I can't recall if the solenoid is active/inactive for operation.

Look it all up in a Motors Manual. This will help you learn how it functions etc. "Home brew" diagrams are fine, once you understand how it all works together. Trying to learn from them is NOT the 'way to go' and the relay was put there (factory) as a safety mechanism, like Joe explained.

You should find one (Motors) in your local Library.

Did you fill the rear housing with (SAE 90 EP) oil??

Good luck.

At home I have a diagram out of an old Chilton's manual that I could scan and send to you but unfortunately I won't be home for 2 months. I also happen to have one of these old overdrives myself that I was going to install but decided to go with a T-5 instead.

What gear is your rear end? I have mine set up to split the gears so that I can actually shift into 6 forward gears, 1st under, 1st overdrive, 2nd under, 2nd overdrive, 3rd under, 3rd overdrive. I don't have the governor set up as that would preclude me from shifting into 1st overdrive which I do use occasionally. I also have a dash light set up to remind me NOT to start out with the truck in overdrive. You've seen the insides of the transmission's overdrive, you know why.

I have had this transmission in this configuration for 36 thousand miles and I am a daily driver year 'round. You will love the overdrive, especially if you have the 3.90 rear, as the math is (overdrive .70) X (3.90 rear end) = 2.73 final drive 3rd overdrive. Depending on your tire diameter you will be loping along at 2000 rpms at 70 mph. Make sure your brakes are up to it!!

Cosmo is correct on the math & it will work like he says too. But there are some "pitfalls" that go with that method, as Mr. Dial points out.

Once you understand it, you'll see the reason for everything being there.

Happy trails.

Thanks to ALL

I have not had time to test the overdrive yet. It has been a real busy summer. Like I said I currently have the original 4.57 rear end and looking for a 4:10 rear which would be 2.87 in 3rd overdrive, currently the 4.57 will be 3.19 in 3rd over which is to much for highway driving. Once I get it set up and running I will let you know how I like it and how well it works for me.

Thanks Steve

Walt

I have not driven it in overdrive yet. I am looking at over all what I would like to have. I use to run my 53 club coupe with 4:11 on the freeway all the time I would just prefer a lower number. You are right though, it's all good. 2.87 just sounds better with engine wear and gas milage.

Thanks steve

A 4:11 with stock tires is 2,000 RPM @ 40 MPH and 3,000 @ 60.

You want your engine between 1,700 & 2,100 and real "tall" gears, are just as bad as to low.

Most run around 3:90 to get the "best all-around".

Happy trails.

I agree with the others, if your RPM's are too low on the highway at speed, your mpg's will suffer, especially if there are any slight hills- you'll just have to give it more pedal or put it back into 4th which kinda defeats the purpose.

Hi to all

I have a few more questions. I have the diagram for the wiring set up. First is will any 12 volt relay work? Do you have to use the original kickdown switch or is there another switch that can be used? Is there something that works that can be obtained at a local electronics shop? If it has to be a kick down switch can I use one out of a ford or one of the other makes? I see them on ebay sometimes? or does it have to be specific to chevy? I have desided to try and set it up the original way.

Thanks Steve

Dear Steve;

Any switch will work, if (that word again) It's the same (electricaly) as the 'oginal' diagram/relay uses.

See; two things occur here. The engine is "killed" for half a second, while the solenoid dis-engages the OD.

You can put it (switch) under the gas pedal or on the carburator. It has to carry a lot of current for the solenoid & relay primary.

This MUST occur at the same time.

Good luck.