Retrofitting TBI and 4l80e

[Greasedog]

Hey guys, looking for a little help on my project. I've got an 84 C10 that I'm looking to do some serious parts rearranging. I'll be installing a TBI fed 454, as well as a 4l80e, while swapping it onto a 4x4 chassis.

Here is where I'm a bit stumped. I know my 80e is going to want to see a 40 pulse per driveshaft RPM VSS signal, but I'd like to retain the stock 84 instrumentation, which includes a cable driven speedometer (cable driven speedo output on the transfer case). I've heard that the speedometer has a built in 4 pulse per cable revolution optical VSS built into it. Is there a way to utilize this existing VSS signal to feed my 7427? I do have a Burn1 and an Extreme ALDL DVD cable, so getting into the PCM shouldn't be an issue. Don't help you guys can provide is greatly appreciated.

[1project2many]

Howdy!!!

Why don't you want to use the trans sensor? That way you can skip the in dash unit. The trans output shaft speed sensor on the 4L80E generates a speed signal. With the 7427 all you'll need to do is use a switch to indicate low range to the ecm. The cable will still drive the needle to give you a visible speed reading so all should be good?

[Greasedog]

I guess I should look at my trans. I thought the speed sensor was in the tail housing in a 2wd 80e, and on the transfer case output shaft. Been a while since I've actually looked at the trans, if it does have an output sensor on it, in just over thinking things. I've been known to do that from time to time.

[1project2many]

http://www.thedieselpageforums.com/photopost/data/500/4L80-sensor01.jpg

[Greasedog]

So is the rear output speed sensor on the transfer case just used for the speedometer?

[buddrow]

In most of the 4wd factory setups Ive seen omit the OSS in the trans and run off of the VSS in the T-case. The 4L80e will operate off of either sensor. If you want to retain the factory cable speedo and add the OSS if its missing from the trans you will be fine.

Buddrow

[Greasedog]

Sweet, thanks!