Is it important for the ECM to see the vehicle speed accurrately for a TPI speed density setup?
I have this in a truck that uses a 4-phase VSS while the TPI ECM is I think a 2-phase. I have to keep the 4-phase so that my speedometer and transmission ECM work correctly, but this causes the TPI ECM to see either 0 mph when stopped, or quickly 255 mph when going only 30 mph.
Is this important? The VSS was not even originally wired to the ECM harness. OR is it only import for the ECM to know if you are stopped or moving which it does now?
Thanks

 

If your transmission is a auto, then yes it is important. The ECM uses your speed to decide when to lock and unlock the torque converter.

 

Hey 2QUIK6, You've got a 4L60E right?? So do I.....for now, anyway. I had to install a second speed sensor to get everything to work right. If you want I can email you what I had to do.

 

93ND500,could you post what you did?That way I'll know what to do.I'm thinking of going with the new E transmission instead of the T56.Come to think of it I don't even like manuals that much.What did you have to do for a ecm/pcm.Thats the only thing holding me back from swapping.What to use for tuning the pcm?

 

Hey Will, that would be great, or post it here on how to hook it up.
There is a way to program the pulse of the VSS in the chip but no one seems to know how, I have a chip that is very close to actual for the TPI, but was for the stock cam, one that CCS MotorSport made me.
Thanks

 

Guys' I will post what I did later tonight......kinda busy finishing up the 406 this afternoon

 

Ok guys' here is the short version. I got all the parts and information from JTR. If you are really going to do this, buy thier guide. It helps alot.

Here is what I did( also the cheapest way)
I drilled a hole in the tranny case<-----not that scary to do. And installed a 4X4 VSS in it. This lets me use the original sensor location to run a 700R4 speed sensor set up.

Parts, prices are approximate.
1) 4X4 speed sensor. $80.
2) Reluctor ring assy. $95.
3) Speed gear clamp assy. $35.
4) Gear/sleeve set. $50.
5) 700R4 VSS. $70-85.
6) my time<-----PRICELESS

After everything is installed, hook up the trucks PCM to the 4X4 sensor. Hook up the TPI computer to the 4-pulse VSS.

There is another route that does not involve any drilling. But it also adds about $200 to the cost.

If you are really going to do this, email me for more a more detailed write-up.


BTW...If you think that tuning the 7730 SD ECM causes hair loss, you should try dealing with the 8625 SD PCM.

 

Does anyone know of a way to just set the pulse ratio in the eeprom? I've seen it done before and have a chip for my TPI that gets it very close to actual, its just that its for my stock cam
Maybe it was the software the guy used that enabled him to do it.
*
Another idea I thought of this morning, wouldn't the ECM for the tranny control the TCC lockup and not the TPI ECM?? After all, the tranny ECM is seeing the correct speed?
I will try to monitor it if I can find a copy of DM for the tranny ECM and compare the 2 ECMs on the TCC lockup flag, this may be part of the surging problem at light accel as I know if the TCC is locked it will surge like that. Never thought to look at it.
*
Will, I guess that book really pays off, but thats sounds like more work than I bargained for on that, who knows I may end up trying to do it, I think I have other problems before this though.
Thanks

 

The trucks PCM will still do the TCC lock-up control. The benefit of adding the secondary VSS is to let the TPI computer know how fast you are going. It is also used for things like, EGR, purge canister, idle control<----also causes surging, etc..... With out a VSS the ECM will always think it's in PARK.

Af far as your tranny, if you do have the 4L60E, it has a 40-pulse per rotation reluctor. While the 700R4's and 4L60's used either a 2-pulse square wave or a 4-pulse sine wave VSS. If you do have a 4L60E and are running its VSS directly to the TPI ECM, it WILL cause problems.

 

Ok, thats the info I was looking for. I do have the 4L60E tranny and the VSS is going straight to the TPI also, it sees either 0 when stopped or quickly goes to 255 mph.
Don't have an EGR currently but will add it soon to pass emissions tests, purge can is not hooked up, but I do have surging idle which may be the heads to I mentioned to you as the chip is not programmed for them.
*
I'm going to get a DM copy for the 4L60E ECM and see what its doing on the scan tool, mainly to make sure its seeing the VSS correctly.
Thanks

 

Here's why:

A SD ecm uses a 4-pulse VSS. With the right drive/driven gear combo, you get 1000 revolutions per mile within the VSS. 4 x 1000 will give you the 4000 pulses per mile. That is what the ecm is looking for.

The ecm in our trucks use something different. Instead of a gear combo, it uses a 40 tooth reluctor and senor. This gives 40 pulses per shaft rotation. Now lets take a truck with a 3.08:1 rear and 29" tires. The drive shaft needs to make 2168 revolutions to complete 1 mile. 40 pulses x 2168 revs gives you 86720 pulses per mile.

This is why you are going to 255MPH so fast.

 

To correct the ECM, you CAN adjust the "Pulses/Mile" for the $8D. The highest value accepted is 921,600. So it may help get the proper reading for the ECM.

As for the speedo that's a different story. There was a post about the "Instrument Display" where there is "bit switch" that can do "coarse" changes. It won't work for a gear chagne from 3.23s to 3.73s, but it has helped with guys who've gone from the 700R4 to T-56.

 

Thats great info Glenn, thanks, I'll have to file this info away somewhere for later. AS for the speedo, it has a separate, "mini ecm" if thats what you want to call it, that is in-line with the wires going to the speedometer, you can change the "mini-ecm" out for different tire sizes.
Now, with that said, I guess the chip in the original stock ECM would have to be reprogrammed for it to be 100% accurate, or maybe the a wire coming off the "mini-ecm" going to the speedo feeds into the foactory ECM....hell now that I think about it one does feed into the TPI ECM as well so I guess thats how it gets adjusted for tire sizes.....I never traced the wires to see exactly where they are going....I've just had to change out the in-line speedo chip before as the tires where changed at the dealer and they didn't chnage the speedo chip.

 

Hooked the scan tool up to the original ECM thats controlling the tranny, and it does see the correct speed and it does without a dout controll the TCC lockup. The TPI unit since its going to 255mph at 10 actual sets the TCC lock almost anytime the vehicle is moving.