'94 Gmc K1500 Auto To 5spd Swap Questions.

GMTRUCKS · June 14, 2011

Hey guys, Just had a few questions that hopefully I can get answers for. Well I just bought a 5 speed transmission for my '94 GMC truck. The package included the trans with 46k original miles, the clutch, pedal, clutch fluid line & reservoir, flexplate, flywheel, transfer case, trans mount, and driveshaft. All for a $100, An offer I couldn't refuse. I also got the computer along with everything. The trans was originaly in an '89 GMC truck with a 305, which is what i have for a motor in my truck. So basically what I'm asking is, Is this computer compatable in my '94? Or are the '89 & '94 computers differant? I know that my Tach won't work if I do this because I know a Tachometer wasn't available until '92. But has anyone done this swap before? Any info and advice will be greatly appreciated! Thanks for reading -Brad

Mike G · June 14, 2011

Most go from stick to auto, why would you want to do this, becasue it was $100? I would just spend another $2000 and buy a truck ready to go. I am no expert, but I would look for a period correct PCM for a 5 speed truck.

Just my $.02's --Mike

GMTRUCKS · June 14, 2011

Most go from stick to auto, why would you want to do this, becasue it was $100? I would just spend another $2000 and buy a truck ready to go. I am no expert, but I would look for a period correct PCM for a 5 speed truck.
Just my $.02's --Mike

The reason I am doing this is because I want to, I didn't buy this to just throw away a 100 bucks. I don't like autos, I just prefer shifting gears manually. But thats just me, I can't speak for everyone else. Thanks for the info on the PCM. Have a good one. -Brad

92rado · June 17, 2011

Most go from stick to auto, why would you want to do this, becasue it was $100? I would just spend another $2000 and buy a truck ready to go. I am no expert, but I would look for a period correct PCM for a 5 speed truck.
Just my $.02's --Mike

The reason I am doing this is because I want to, I didn't buy this to just throw away a 100 bucks. I don't like autos, I just prefer shifting gears manually. But thats just me, I can't speak for everyone else. Thanks for the info on the PCM. Have a good one. -Brad

I think its pretty cool Idea! My truck is a 5spd and I Love it! Its a Hell of a lot more fun than a auto. But that's just my opinion. Let us know how it turns out.

nht mike · June 19, 2011

I had both an 89 and a 94 two wheel drive with manual trans. In 89 the only trans you could get was a light duty Getrag. It was a close ratio and you couldn't get the tow package if you ordered it. In 94 you had your choise of a New Venture 3500 or for about $63 more you could get the NV4500HD. I ordered the 4500 and the tow package and it worked great for me. There is quite a bit of difference between the 89 and 94 engine. The 89 as an air pump with the manual and the 94 doesn't. In general my 94 ran better than the 89. I would just go with the ecm you have. One thing you will have to change or have recalibrated is the DRAC. It's a converter that changes the analog signal from your speed sensor to something the speedo and the ABS ecm can read. If I could have had a manual in my new truck that's what I would have ordered.

Furno · June 19, 2011

OK,

first off. I need to know what engine you have and the number on your current computer and also which trans you currently have (is it a 4L60 or 4L60e? or a 4L80?)

then I need to know the engine that your new setup came from, and the number on the new computer.

After that, I can get out the book and tell you the exact differences in the pinout on your harness and the new computer. At most, you may have to do some minor modifications to the harness (bot not likely at all, and they are generally easy to do)

The main differences will be that you will no longer be using the trans plugs and it may make the computer act a little funny with the loose ends.

and you will need to add in a clutch switch for safety so that you cannot start it in gear. If you're not gonna add this switch then I won't help you. totally dangerous without it. got pinned against a wall when I was a kid because of some shadetree mechanic thinking it wasn't necessary. Luckily it was just a subaru brat.

As far as your DRAC and speedo, find out if your tire size and rear end ratio were the same on both trucks, if so then you should be good, if not then there are plenty of electronic ratio adapters available, or you can change out the drive and driven gears which is not hard to do either.

Oh, and you should not have a problem with the tach, that should still work. My 91 has a stock tach, who told you they weren't available before 92?

GMTRUCKS · June 19, 2011

I had both an 89 and a 94 two wheel drive with manual trans. In 89 the only trans you could get was a light duty Getrag. It was a close ratio and you couldn't get the tow package if you ordered it. In 94 you had your choise of a New Venture 3500 or for about $63 more you could get the NV4500HD. I ordered the 4500 and the tow package and it worked great for me. There is quite a bit of difference between the 89 and 94 engine. The 89 as an air pump with the manual and the 94 doesn't. In general my 94 ran better than the 89. I would just go with the ecm you have. One thing you will have to change or have recalibrated is the DRAC. It's a converter that changes the analog signal from your speed sensor to something the speedo and the ABS ecm can read. If I could have had a manual in my new truck that's what I would have ordered.

Hey thanks for that info NHT Mike, Really looking forward to this. I really looked hard for a 5spd truck when I was truck shopping, But when I found one, The truck was either rotted or was to expensive. But is it okay to use the ecm I have? Because since my auto is elec controlled I didn't no if it would mess up the ecm if I just disconnected the trans control harness. -Brad