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1970 Chevrolet Pickup - Overdrive = Fourth Gear?

I have a 1965 c 10 with 3 speed manual with factory overdrive. is this supposed to be fourth gear because it doesnt seem to do anything rpm wise.

Yes, I believe OD is supposed to be the 4th forward gear. Something’s amiss w/the selection of that function apparently.

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Usually the difference between 3rd and OD is about 30%.

Do you mean There is no difference between rpm in 3rd and overdrive or do you mean you think the highway rpm is higher than you expected.

In the days when people were using pickup trucks as working trucks they were expected to be able to haul heavier load than they were rated for and even pull stumps with only 3 speeds. By necessity they were geared low.

Today when they are used as commuter, road trip and mall crawl vehicles, they have many more speeds and are expected to go down the interstate at 2000 rpm or less.

Don’t forget, pickups used to cost less than the cheapest sedans. Today most sticker 40 to 60 grand. Who is going to pull stumps with that?

Does your C10 have the shift on the column and a separate control.for the overdrive?
If this is the case, your truck has the Borg Warner overdrive. When the overdrive is engaged (control knob pushed in), you accelerate to above 30 mph in third gear and let up on the accelerator. The overdrive should then engage and reduce the engine rpm. Until the overdrive is engaged, the truck freewheels–letting up on the accelerator is like depressing the clutch. When the overdrive control knob is pulled out, the overdrive is locked out and the truck behaves like a normal 3 speed manual.
I have never seen a Chevrolet truck with the Borg Warner overdrive. I have driven a 1969 Ford F-100 with this feature. If your truck has this feature, you actually have 5 speeds, as the overdrive can be engaged in second gear which gives you a gear ratio a little below direct drive third gear.
As I remember, the overdrive is controlled by an electronic solenoid. If your overdrive is not working, you may have an electrical problem.

Thanks for the info. when i originally purchased the truck i was told lever pushed in was normal and pulled out was over drive. maybe thats why it doesnt appear to be doing anything.
I will try the opposite the next time its out and see. thanks again

I dont notice rpm change between 3rd and overdrive

thought so thanks

@Chuck59. Every overdrive equipped vehicle I have ever driven or ridden in is set up so that the overdrive is engaged when the lever is pushed in and locked out when the lever is pulled out.
The Both Warner overdrive was standard on the Willys Overland station wagons with the four cylinder engine. It was a popular option on the independent manufacturers’ cars–the Nash, Studebaker, Hudson, Packard and Kaiser. Chrysler had it as an option on some models before WW II and began offering it again in 1952. The overdrive became available on Ford products beginning with the 1949 models. Chevrolet was the only GM product to offer the overdrive and it became an option in 1955. It ceased to be available sometime in the mid 1960s. A Chevrolet truck with overdrive is exceedingly rare. I have seen Ford and Studebaker half ton pickup trucks with the Borg Warner overdrive, but I have never seen a Chevrolet or Dodge pickup with this option.

Then something is broken, no surprise on a 50 year old truck.

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probably why i cant find much info on the subject. seller said it was factory over drive. again thanks