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speedometer bouncing

H

hereismylife

formerly j k auto
Messages
252
Reaction score
1
Location
pa
It used to do it after 75 mph it would just go backwards by 5 to 10 mph.

If you go over 85 it would not go any faster then 75 mph and bounce 5 to 10 slower but never go over 75...

Now it will go to 55 and not go past it. It just bounces around 45 to 55 mph

I ran the tech program and it shows the same as the speedo. I also go the speed sensor code. I erased the code and it did not pop up again and the spedo still bounces around....

What do yas think is the vss sensor no good...?

thanks
 
The grounds are ok I doubled them a year ago. I have 4 eight guage wire. 2 from batts to engine and 2 from engine to frame. also the smaller grounds were cleaned at that time. I put protector on all the grounds.

You say the ones at the dash. Which ones?
 
My first thought was, there is a motor that drives the needle. Maybe its bad, a striped gear, loose wire....? Does the odo work?
 
I read different issues with this except most did not move or work anymore. Also there were other issues like mine but not like mine. This is where I got some of my info. Anyhow thanks for the help so far.

I am going to see about testing the vss sensor while driving down the road. I am thinking on probing the sensor and seeing if checks out.

I just need to know the output of the sensor up till 75

I am going to keep checking things out till I get things fixed.....

thanks
 
Is it acting like the gears are physically slipping? Maybe its on its way out, mechanical failure... How many miles on this Speedo/ODO?
 
I do understand about the slipping but if it was I think it would just drop off faster. It just stops at 55 to 60 and the faster you go the slower the speedometer reads it just starts going backwards...

Does anyone know how to test this sensor on the transfer case "vss"

thanks :thumbsup:
 
The 1st thing I'd check is that the vss isn't clogged with metal filings.They are magnetic and will attract any metal filings and other gunk. If it appears clean ,drive with scan tool attached to see if the speed signal increases with speed. Check all connectors for pushed out or bent pins.
Is the transmission functioning correctly?
VSS buffer is also suspect
 
Well I cleaned the sensor and all is good there.

I will use the scan tool i got from sweeden on here..

I also am looking for another problem?

How many pulses does the ring put out on the transfer case?

I think it is 40

But I need to know

HOW MANY IN A MILE.... IS IT 2000 OR 4000???????
 
bk95td said:
The 1st thing I'd check is that the vss isn't clogged with metal filings.They are magnetic and will attract any metal filings and other gunk. If it appears clean ,drive with scan tool attached to see if the speed signal increases with speed. Check all connectors for pushed out or bent pins.
Is the transmission functioning correctly?
VSS buffer is also suspect
Click to expand...

Yes the scan tool shows that the speed drops off like the speedo does...
 
How did you wire yours in the conversion? Did you leave the stock VSSB and associated wiring in place and then use the 2 speeed sensors on the 47RE to control it? How are you reading your speed with the scan tool? Are you reading it via the ABS controller, or did you leave the ECM in place to do some controls. Just trying to visualize how you wired since this isn't a stocker. If you are reading your speed via the ABS, then it could be your VSSB or VSS. The 6.5 in stock form has a 40 tooth tone wheel on the output side of the transfer case and the VSS sends a voltage to the VSSB that is generated by the magnet in the VSS from the tone wheel going by it. The VSSB then reads the signal and then outputs a 4,000 PPM signal for the ECM. Two 2,000 PPM signals, one goes to the radio and the other to the speedo and ECM. And then a 128,000 PPM signal to the ABS controller. If you need anymore details I have some schematics from my conversion I could send you that may help out. Alos if you haven't figured out your gear indicator I may have a solution for you on that as well.
 
Last edited:
update it is fixed...

I finally came to the conclution it was the vss sensor. I did some testing for the week and replaced it and it was fixed...

I used the chevy vss sensor in my conversion. my tech tool also verified that the speed sensor was faulty..

Thanks for the help with the pulses and I got both my trans and dash now on the same vss sensor on the t case......:thumbsup:
 
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