Electrical Gurus.... help?

[Chevycrew]

Is there a way to change the amount of pulses that the PCM sees for the VSS?

I need to multiply the VSS pulse signal to the PCM by 2.72. This would also need to be selectable.


I think (may be wrong) that the pulse per revolution is something like 40, I need to be able to throw a switch, and have that be 109 pulses per rev.


FYI: Chevy PCM and VSS, 02 TrailBlazer


Thanks!

 

[DaveB]

There are electrical circuits that could do that but would most likely require a custom design. There are speedometer T connectors that allow two VSS units to be used at the same time. You could use two different units and switch the signal going to the PCM between the two.

 

[MikeGyver]

http://cgi.ebay.com/ebaymotors/DAKO...ccessories&hash=item564629394e#ht_2858wt_1381

http://www.healtech-electronics.com/ Speedohealer

Now I'm curious what you're doing

 

[Chevycrew]

Basically I need the pcm to see the right speed so my trans shifts right when in 4 low, instead of moving the vss forward to the trans, I can just multiply by the 2.72 and be done.

I would just need to be able to swap between the stock and modified signal.

 

[DOSS]

It may be easier just to move the VSS forward instead of having a pain in the butt electrical setup that you have to remember to flip a switch every time you are in 4 low. KISS

 

[Chevycrew]

I want my speedo to work in 4 low, moving it forward wont do that.

Speedohealer should work great with 2 different settings to swap between, stock, and low range.

 

[bigblock72]

Most PCMs use an input from the t-case controller to tell the PCM when low range is selected and then will modify it's shift strategy and also keep it from setting incorrect gear ratio codes. What computer are you using and I can probably tell you what wire to connect to make it work.

 

[RockChucker]

you might try to talk to waynehartwig on here. he is a gm computer master for sure. i'm getting ready for a 5.3 swap in my TJ and he will be doing the tuning for sure.

 

[Chevycrew]

I'm using the stock pcm, tuned by Wayne. I already have ditched the T-case controller and I have the pcm input hooked to a switch for 4 low.

This addition of the speedohealer will be for my 2nd T-case... Which seems to be about the only electrical option.


I guess part of the confusion is my fault for not giving all the info.


Im running dual cases, everything is hooked up and fuctioning correctly for my front case, or single low range. The addition of the speedohealer is just to make my trans and pcm happy when in low-low.

 

[jackjoh]

Help me here, why do you care what speed you are going in low range? I would think it would be sound and gut feel that guides you. A tach also helps. What am I missing?

 

[Chevycrew]

My speedo works in low range, and I dont care about low-low, other than the PCM needs the proper reading for the transmission to shift properly.

 

[bigblock72]

Im running dual cases, everything is hooked up and fuctioning correctly for my front case, or single low range. The addition of the speedohealer is just to make my trans and pcm happy when in low-low.

That makes sense. In that case the speedohealer is really your only option besides moving the speed sensor to the output shaft of the trans.