Sleeper_Z

iTrader: (1)

Hi,
I am getting an 84 3/4 ton 4x4 chevy truck tomarrow and I want to put the TPI setup off my 92 Z28 on it sence I wont be needing it after the LS1 swap. BUT I dont know what to do about the VSS. Can I run an autometer electric speedo and just bypass the mechanical one all together?? Will the T5 VSS bolt to the TH400?? Im at a lose here. Any help would be greatly appriciated. Thanks a million.

Jeremy

Jay

iTrader: (2)

i'm doing the same thing shortly, I decided to just buy the adapter from JTR. It's not cheap, but it lets you run the stock mechanical speedo and supplies the correct VSS signal for the ECM.

dyeager535

A few different ways to run VSS on those trucks.

Stock '82(?)+ all speedometers are equipped to utilize the 2000PPM VSS setup. Cruise is what determines if they have VSS, unless the truck is CCC (CA only) or TBI (1987-1991, "old" body style) 1992 TPI ECM is looking for 4000PPM if I'm not mistaken though.

1990-91 speedo's are electric, and utilize a DRAC that takes a 40 pulse VSS signal from the transmission or in 4WD, transfercase. DRAC can output 2 or 4000PPM, plus 128000PPM for ABS. In your case, transmission has nothing to do with VSS since it's 4wd. Speedo takes the 2000PPM signal.

1990-91 Suburban, Blazer/Jimmy, cab/chassis, and crew cab are donors for the cluster. It's a bolt in for your truck, but will require some repinning/rewiring (easy) of the cluster connector.

Unless you replace the t-case with a 90-91 NP241 (as opposed to your NP208) you won't be able to go full digital. But if you swap the t-case, you could run the DRAC. (or anything else that works off of the 40 pulse setups) You'd have to do some research regarding whether it's output is what the 1992 ECM is looking for though. The early cable drive speedo's aren't problematic per se (they are approaching 15 years old at the youngest now) but when they do act up, it's annoying, and one of the reasons I ditched mine.

Sorry I can't answer your exact question, but I put 1988 TPI in a 1986 K5, (same truck) originally with the VSS in the speedo, but just converted to the 90-91 speedometer/DRAC setup. The later year of your TPI setup introduces some variables I didn't have to deal with, thus no exact answer for you. Hopefully some of this info is helpful though.

Jay

iTrader: (2)

My 86 K10 doesn't have a VSS, no computer in at all.
Pretty much the adapter from JTR is the simplest way I have found to supply the ECM with the 4000 pulse signal needed.
http://www.jagsthatrun.com/Pages/Spe...eedometer.html
part # speed sensor, 4PAC - $79

dyeager535

It may not have come with VSS, but the speedometers are all the same '82-89, and you can bolt the VSS buffer to any of them. Also not relevant if the ECM requires 4000PPM.

Jim85IROC

iTrader: (2)

Try doing a search about speed density computers and VSS's. I thought I remembered that the SD computers could be set to work with a 2000PPM or a 4000PPM, though I might be thinking of something else. If it can, then you should just be able to get a VSS out of a tbi 87-91, or maybe the whole speedo if you need it to work with the VSS.

Fast355

iTrader: (2)

My 1983 is using the DRAC and cluster from a 1992 and a later model 4L60 non E.

Jay

iTrader: (2)

Jim you are right.. I forgot about that..
you just uncheck the option for it.. i don;t know off hand what it is, but if you look at one of the flags in the 730 .bin one option is for magnetic VSS and I think you just uncheck it.
And from what dyeager535 says, you could do exactly what you said and just use the optical VSS on the speedo.

Sleeper_Z

iTrader: (1)

Wow I didnt expact such a responce. Thanks for all your help and info. Ill have to see if I can find a 90-91 blazer around. Thanks agian.

Jeremy

Jim85IROC

iTrader: (2)

Those are sometimes hard to find, but since Jay confirmed that the 730 ECM can be configured for either 2k or 4kPPM, you can use the cluster out of any truck that had a VSS, including all of the TBI injected trucks, and anything with cruise control back to whenever they started using the VSS to control the cruise. It should open up your options considerably.

Sleeper_Z

iTrader: (1)

Oh ok, thanks alot for pointing that of for me. I dont know if my truck has cruise or not. Ill have to look. I just bought it off a friend and its still at his house. Thanks again for all your help.

Jeremy