12200411 set up for 700R4

[EagleMark]

It's a full size Blazer. I'm pretty familiar with the wiring on that end, just forget what to do on 1220411 end? He says it's done, but I like to make sure things are done right and check operation, considering there's no noticeable sign of TCC lock up? But with the wrong VSS signal who knows what the speed is recording? I've never driven it and months ago it was a truck without a motor, 5.7L TBI and 5.3L sitting on floor.

Do you happen to have that second page as a full page? I don't have that diagram...

[dave w]

I think adjusting the Speed Pulse Per Revolution will correct for the Dakota Digital 8K pulse. The idea I have is to get the Speed Pulse per Mile to be 8000. Here is the link to a post I did about a week ago: http://www.gearhead-efi.com/Fuel-Inj...gital-SEN-01-1

I don't know if this really works, because the vehicle I flashed the PCM with these changes is not on the road yet.

dave w

[mecanicman]

I tried this once before, didnt make it work so I hooked it back up through the vacum switch. I believe the pcm needs to see the vehicle in gear before it will apply the tcc. Not having a prndl switch it will not see in gear. Might be able to make it work, I just found it easier to leave it with brake switch, vacum switch, 4th gear switch setup.

[Buzz]

Lots of good ideas in this thread already ...

Dave W - you figured it out (despite your lack of a road test) - with a pulse generator (typically being driven by a speedometer cable) would want the VSS pulses per mile (H0101 in EFILive) in the tune, to equal that of the pulse generator (4K / 8K / 16K). It doesn't matter what speedometer parameters you change to arrive at this value - as long as in the end the correct value is displayed.

The PRNDL tells the PCM what position the gear shift is in - not what gear the transmission is in - there are two different PIDs in the EFILive ScanTool that correspond to gear shift position (GM.PRND) and the current gear the transmission is in (GM.GEAR). You could get an input to the PCM for the gear shift position with a 700R4, but not for the current gear (as it is a non-electronic transmission).

TCC lockup ... is another issue ... most people who run a non-electronic transmission (TH350 / TH400 / 700R4) behind an LSx engine with a PCM, will either run a manual transmission tune, or an automatic tune with pretty much everything disabled. Obviously, a manual transmission tune cannot control the TCC lockup. An automatic tune could do this - but not without a proper transmission current gear signal - which the 700R4 cannot provide.

Most people elect to simply have the 700R4 lockup in 4th gear only, as already described in this thread. Unless the vehicle is underpowered, or will be used for towing, there is no need to use a vacuum module as a component of the TCC lockup system. Ignition voltage routed through a brake pedal switch works just fine.

There is another option which I have never tried (I don't get much call for non-electronic transmissions) ... running an automatic tune, but with the transmission type changed from 4L80 or 4L60 to "non-electronic automatic". I wonder if this MAY let the PCM control TCC lockup based on VSS only ... who knows

[RobertISaar]

Do you happen to have that second page as a full page? I don't have that diagram...

i could grab it, but boy is it large, ugly and confusing for me. it was from the S10 blazer though.... can't find that exact style for the 90 full-size. different years.... maybe.

[EagleMark]

i could grab it, but boy is it large, ugly and confusing for me. it was from the S10 blazer though.... can't find that exact style for the 90 full-size. different years.... maybe.

Thanks but no need. Only interested if it was for 7747 type ECM.

[RobertISaar]

90 blazer S10 4.3 might be 7747?

[EagleMark]

90 blazer S10 4.3 might be 7747?

Same C3, probably a 288 or 299? I'd like one for that if 700R4? If it's huge and hard to work with like you said we'll just pass.

Buzz, mecanicman, Dave, thanks, I think I got it for the VSS.

But TCC will only work in forth? With no speed? This I'm not clear on... I could get only one signal from P/N is grounded, when in D/R it is an open signal, could run that through relay. But no more, couldn't get all gears.

Actually forth is fine and not even going to shoot for third. Truck has good gearing for 35 inch tires but I've had enough of these to know third is not worth it.

[RobertISaar]

http://i.imgur.com/5GbtscH.png

for some reason, i didn't rotate before uploading....

anyways, that style of diagram confuses almost as badly as the stuff chrysler released for most of their OBD1 vehicles.

[EagleMark]

Thanks Robert!

Back to 700R4 and lock up only in fourth gear...doesn't it need some kind of VSS from PCM to lock? This vehicle trans was controlled by ECM that has speed, no vacuum switch which IIRC only came in pre 87 Chevy Truck 700R4.