1991 speedo problem

[MightyFine69]

My 1991 fullsize Blazer is four wheel drive. It has an NP241 transfer case. I was having a problem with my speedo not working, so I replaced the speed sensor on the transfer case. My speedo started working, but recently it has started bouncing again. I replaced the sensor about two weeks ago. Does anyone have any idea why the sensor would be puking already? How does the sensor work? Does my transfer case need rebuilding?

[Grim Reaper]

Originally Posted by MightyFine69

My 1991 fullsize Blazer is four wheel drive. It has an NP241 transfer case. I was having a problem with my speedo not working, so I replaced the speed sensor on the transfer case. My speedo started working, but recently it has started bouncing again. I replaced the sensor about two weeks ago. Does anyone have any idea why the sensor would be puking already? How does the sensor work? Does my transfer case need rebuilding?

91 sould have DRAC. It covertes the stuff from the speed sensor into usable info for the cruise and ECM. That is probably where your problem was but for what ever reason messing with the sensor got it straighten up. Or the Drac is out of range and over loading the speed sensor.

[MightyFine69]

DRAC? What in the world is that? And where is it located? Is it easy to fix and inexpensive or am I going to have to be a contortionist and give up my left leg for it? Thanks for your reply.

[Grim Reaper]

Originally Posted by MightyFine69

DRAC? What in the world is that? And where is it located? Is it easy to fix and inexpensive or am I going to have to be a contortionist and give up my left leg for it? Thanks for your reply.

Not sure where it's mounted. My truck is not new enough to have it. What the DRAC does is convert the signal from the VSS to a pulse that the ECM understands. If I had to guess as to where it was I would say it's probably with the ECM behind the glove box. I would go into the Main forum or go over to www.ck5.com and ask inthe garage and see if Dorian (Deyager) or Doug (K5mutt) sees it. They know those years FI pretty well. Doug is also here. I think he;s 76Chalet here.