Thread: Transmissions for a LS motor - 5 spd vs. auto

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I've just decided to drop the idea of SBC crate motor and instead go with a LS motor for my 1967 1/2t 2wd GMC pickup project. It looks like there are a few 4.8l motor/5 speed combo's from early 2000s chevy trucks - but they aren't easy to find, plus I'd rather have a 5.3.

It looks like 5.3 with auto trans is pretty easy to find. Are the newer auto trans "drive by wire", meaning I don't need a column shifter, just something like a push button that would tell the trans to shift? My truck is a 4 speed, so I don't have a shifter on the column.

I'm thinking that if an auto trans is an easy install, I'll look for wrecked chevy truck with 5.3ls motor and auto trans and install that. That still leaves me with the option to install a 5 sp (nv3500 or nv4500) down the road.

Thanks for any advice!

"Newer" transmissions include the 4L60E, 4L65E, 4L70E and 4L80E. The shifting is electronically controlled, once you're in overdrive (4th), but you need a mechanical shifter to shift from park to reverse and OD. The mechanical shifter can also be used to manually shift down to 3rd, 2nd, or 1st. You can get a floor mounted or column mounted shifter, but the column version would be part of a new or used column, made for a 4 speed automatic.

Even more recent auto transmissions are 6 speed. One problem with them is substantially larger exterior dimensions, that may cause problems. All of them (4 & 6 speed) will be longer than your old transmission mount can handle.

You'll also need an electronic controller for the transmission - it won't work without it. Trucks from the factory will have the engine and trans controlled by the same computer. At a salvage yard, you'd need to get everything from a donor that is possible - the engine, column/shifter, computer, trans and wiring harness. There's quite a mess of wires to deal with - around a hundred in a typical engine and trans wiring harness.

I chose to use a GM connect and cruise package for my car. It include the LS engine of your choice (430-556hp), an appropriate 4 speed auto trans and all of the needed electronics to make it run. The engine's computer is separate from the transmission computer (supplied by PCS). It's not a cheap route though (starting around $10K), but there's little to do put hook up a few power-source and ignition switch wires.

LS Trans & Engine Packages

https://www.powertraincontrolsolutio...on_Controller/

I found that the floor shifter that Lokar sells as 4L60E compatible, does not work properly with the newer 4L65E (and probably none of the other higher numbers). I made one work, but it required a change in the lever arm length to better match the travel required by the trans. The shifter had about 10% too much travel.

Another issue you'll have to deal with is a major change to the fuel pump setup. The newer LS engines require 58 psi. I have an in-tank pump from Tanks, plus a special pressure regulating filter, with a return line to the tank.

http://www.tanksinc.com/index.cfm/pa...prod/prd84.htm

http://www.tanksinc.com/index.cfm/pa...rod/prd425.htm

Thanks Dave, I appreciate the info. I've decided to get some body work done on the truck and that will give me 6 months to search for a used ls motor and 5 speed trans. Since I really want a 5 speed in the long term, and an auto trans wont be a completely simple install that I could undo easily, I'll just keep looking for a 5 speed.

I'll start a new post with my questions about the different 5 speed trans options. I'd love to go with the GM connect option, but it's way out of my budget.

Thanks for the suggestion about the fuel pump and fuel filter!

If you're talking a 5 speed manual, the NV4500 would be the best bet. They were available behind LS engines, but may take some searching to find one. The price shouldn't be horrible though. I can get new diesel ones for $1400.

You can also use the older style chevy automatic tans by either using an adapter flex plate or a hub that bolts to the LS flex plate. I have a standard 700r4 behind my 5.3.