Motorhome with gm 480le transmission

[Motor home]

Anyone know what would make speedometer stick wide open?

 

[Will L.]

The check engine light wont come on, but you may have a stored code to narrow it down too.

Short in the harness from the toss at right rear of trans or vssb issue.

Is it shifting hard or going into limp mode?

 

[Motor home]

What is vssb?

 

[ak diesel driver]

Vehicle speed sensor buffer

 

[Motor home]

Vehicle speed sensor buffer

Is that inside the transmission?I just had it rebuilt and havent got it put back in.Hoping it will work ok when i get it back in.

 

[Will L.]

No. Once you get the trans installed, see if it works. The toss is partnof the trans and could have been the issue.
For now, inspection of the harness that plugs into the trans is worth while.

 

[Motor home]

Thanks

 

[THEFERMANATOR]

What year and engine combo? Not all use the vssb, only gassers up to 95 and 6.2/6.5l diesels.

 

[Motor home]

1992 monterrey by cobra motorhome.I believe it is a 454 engine(chevrolet).Can u explain what vssb is?

 

[THEFERMANATOR]

Vssb is the vehicle speed sensor buffer. It converts the a/c signal from the vehicle speed sensor into a square wave signal for the speedometer and other modules. That said, your 92 may or may not use the vssb for it's speed signal. I know 92 4x4's wired the trans output speed sensor directly to the ECM, but I honestly am not sure how 2 wheel drives were wired. That said, I'm pretty sure 92 did not use a vssb, but instead used a DRAC(digital ration adapter calculator). It did the same basic job, just wasn't as complex. As to your speedo going full bore over, it takes either a high pulsed signal, a good deal of a/c voltage, or a failed resistor in your speedo board to do this. You normally start by unplugging your drac/vssb to see if this brings the speedo back to 0(I have no idea where it would be in a motorhome, in a pickup yruck it is normally mounted below the ecm behind the glove box). If that does it then I would next plug it back in and then unplug the vehicle speed sensor and see if it stays at 0 or goes all the way over again. If unplugging the drac/vssb doesn't bring the speedo back, then chances are your speedo has failed.