Overdrive unit

[1984chev]

Hey I have a 1984 chevy k10. It has the th400 transmission with a shift kit. I was wondering where to get a cheap overdrive unit and what kind?

[andrewmp6]

Cheap would be a used gear vendors and those go for 500 to a grand and is a crap shoot if it works right.

[1984chev]

Don't work good with that tranny?

[donut]

From what I've read, works good with that transmission. Cheap/used IMO is the crapshoot.
4l80e swap is a possibility.

Get a tach and observe your cruise rpm and decide if OD is right in your case.
Old K-20 I had it would have made sense, however I'd still be paying for the swap (sold the truck 3 yrs ago) Current C-30, I get 1-2 mpg less than an injected, OD truck. In my mind, it makes more sense to optimize the engine for the powerband. In some cases, the OD can lug the engine and make mileage worse.

[GRADYS Performance]

What do you do with your truck? Daily driver, heavy towing, How much do you carry if loaded? You have several options depending on your use.

[andrewmp6]

Yeah a used gear vendors will bolt on but if the unit works good being used is the crap shoot.The other options are a trans swap 700r4 or 4l80e,What t case do you have in it now?

[tucsonjwt]

Gear vendor advertises 20% improvement in fuel economy with non- lock up torque converter automatic transmissions, or manual transmissions. My 83 C20 came with a gear vendor. A gear vendor does not work below 30 MPH (I think) and with my manual granny 4 spd it is only used in 4th gear (maybe 3rd if I really wind it up, but that defeats the purpose of a gv unit.)

Used gear vendors are not cheap - I see $1000-$1500 with all of the electrical controls and the adapter required for your specific transmission. A shop in Las Vegas used to sell rebuilt units for about $2000, as I recall.

Getting a modern automatic transmission would be a better choice, IMHO. But I would not expect the additional cost to be covered by improved fuel economy unless you drive 50,000 miles a year - on the highway.

[greg64]

1984chev, what gears do you have in the axles anyway? A gear swap may accomplish what you're looking for, and at a lot more reasonable cost then the transmission swap.

[1984chev]

Well I drive it on the weekends basically, and often for pulling small trailers with 4 wheelers dirt bikes and so on. But when you get up to that 55-60 mph range she's at about 2800 rpm.

[72MARIO]

I went with a gv mainly for driver comfort by reducing the rpm.. A light duty truck would be best with a 700r. Any heavy towing I would recommend a 4l80. The gv is a very expensive choice. I got a great price on mine. My othere truck will get a 4l80