VSS question for manual trans swap

[rwd_pete]

I'm getting close to starting an LT1 swap into my '78 Malibu. Currently the car has a Saginaw 4 speed.
According to the '96 GM manual the Vehicle Speed Sensor buffer sends two signals to the PCM. The first is 2002 pulses per mile that is used by the engine. The second is the transmission case 40 pulse per revolution signal that is used in order to control the transmission.

If I wanted to maintain the 4 speed manual trans, would one of these signal generators, driven off the speedometer cable be of any value? They indicate 4000 puses per mile. Different advertisements for the same unit indicate that they work with LT1's.

http://www.summitracing.com/parts/rpc-250-4153

If 4000 is not suitable, can the people that reprogram PCM's use the 4000 pulse and tune the PCM to manage the engine with it?

Satisfying the engine management is more important than a speedometer. I can get my speed off my phone/fitbit app. It thinks I'm a fast bicycle rider.

[Injuneer]

Not sure exactly what your plans are for a transmission. The 4L60E VSS is the one that produces 40 pulses per revolution of the output shaft. The T56 manual produces 17 pulses per revolution. The PCM has to be programmed for either the auto or manual trans, so it knows which pulse signal to expect. IT has to know the MPH of the vehicle for certain functions. It uses the pulse signal to determine the trans output shaft speed, than calculates the MPH by using the rear axle ratio and the rear tire diameter, both of which must be programmed into the PCM.

What year is your PCM? Is it for an auto or manual trans? What trans are you using - if you want to use your current 4-speed manual, you would be best to use a PCM with a manual trans program. The PCM (assuming it is 94-97, 93 is a different story) will be trying to control an auto trans shifting and lockup, if it has an auto trans program, so you will need to have certain codes programmed out. The manual program will only try and control things like the skip shift and reverse lockout solenoids. Those are easily programmed out.

[rwd_pete]

I was thinking about my using my old Saginaw 4 speed which has no pulse generator. That was the original question on how to make that work.
I have a 4 L60E that came out of a 1994 L99 car and that PCM 16188051. From what I understand the 94 trans convertor locks up different than the 95 trans. I assume the PCM would need to be reprogrammed for the 350.
I have supposedly a 95 Vette computor 16181333. I'm not sure if it was a standard or automatic car.
The engine is a rebuilt iron head LT1 engine with a '95 Corvette cam.

Tomorrow I am going to a local wreckers. They just got a '95 Caprice in and listed the trans for $99. and the PCM for $25. I thought I would try to get both. Hopefully they are still there. So a 4L60E combo is one option. I have a standard flywheel for an 11" clutch, one piece rear seal engine, that would would work with the current belhousing and trans in the Malibu. The standard trans is nice to drive. It gets back to how to get the proper VSS signal if I use the old standard trans, if it is possible.

[Injuneer]

Where in the 96 F-Body factory manual did you find the comments about the "Vehicle Speed Sensor buffer"? I looked through the manual but couldn't find it. As far as I know, the VSS setup for the F-Body LT1 is the same for all years - a single reluctor wheel/sensor wired directly to the PCM. I did notice on the wiring diagram for the dash, there was a reference to splice #242, but that is splitting the PCM output signal 4,000 PPM to feed the speedo, cruise control, BCM and radio. Did not find a reference to a 2,002 PPM signal. Is it possible you are using the Y-Body manual?

The point I was trying to make with my post was to note that you need to feed the PCM with either a 40 pulse or 17 pulse per trans output shaft revolution, depending on whether it's programmed for the auto of manual trans. So that would be the output of your cable driven signal generator. The PCM has to process that signal to integrate the rear axle ratio and the tire diameter. Then it sends a 4000 pulse per mile to the instrument cluster, cruise control, etc. The Jags That Run site addresses a lot of this.

If you are using something other than a 4th Gen (94-97) F-Body speedo, you would need to convert the PCM's 4,000 PPM signal to whatever pulse/mile signal is required by the speedo. Dakota Digital has a universal speedo signal converter (SGI-5). I use the SGI-5 to convert the 40 P/rev signal to the 17 P/rev signal that my manual trans programmed stock PCM is expecting.

There is a sticky thread that addresses the differences between the 94 switch converter lockup and the 95 PWM lockup signal, which you may already be aware of:

http://ltxtech.com/forums/showthread.php?23419-4L60E-year-differences-and-interchanges

[rwd_pete]

I found those details in the transmission section (page 7A-134) of my 1996 B body manual.
http://ltxtech.com/forums/attachment.php?attachmentid=34620&stc=1
From the Jags That Run website it looks like a relcutor wheel on the rear axle may be the only option to connect the PCM to vehicle speed with an old transmission.
http://ltxtech.com/forums/attachment.php?attachmentid=34621&stc=1
From the LT1 swap website he inidcates he can program any PCM to accept any number of pulses.
http://www.lt1swap.com/programming.htm

“VSS-If using a non electronic trans, You should KEEP a vehicle speed sensorregardless of what transmission type you use. ThePCM needs to know if vehicle is moving. Without the speed sensor, you cansuffer from reduced fuel economy, reduced power, and idle problems. Thereare a few options for speed sensors on the transmissions with cable driveoutput. View this link at DakotaDigital (http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=109/category_id=311/home_id=59/mode=prod/prd109.htm)website. I have used Dakota Digital SEN-4160 withgood success. This is a 8000 pulse per mile sensor, that will allow cablespeedometer hookup. (SEN-4160 WILL NOT WORK WITH DRIVE BY WIRE CRUISECONTROL, You must retro-fit a higher pulse sensor if you wish to use cruisecontrol with drive by wire.) I can program most any PCM to accept any # ofspeed pulses. (1996,1997 Black Box Vortec PCM will not accept 8000 pulse input) Alsocheck out www.jagsthatrun.com (http://www.jagsthatrun.com/)for other speed sensor options. (Must output a SINE wave signal, or A/C Voltage)”

I had read that sticky regarding the '94 trans, which is why I bought this other '95 trans yesterday. Unfortunately is was an L99 car, so I didn't take the PCM. I have noticed that the LT1 swap I did before had a TCC switch and both L99 harnesses I have don't have one. In the manual it indicates that it is only for 350's. I wonder how important having one is?
http://ltxtech.com/forums/attachment.php?attachmentid=34622&stc=1
Thanks for your comments.

[Injuneer]

The B-Body and F-Body systems must be significantly different. Searching online, I see discussions of the DRAC and VSSB modules for the B-Body.

http://www.impalassforum.com/vBulletin/archive/index.php/t-272165.html

That VSS feeds a VSSB unit that is an outboard unit, typically under the dash. Check the wiring diagram in the B-Body manual for the VSS - is should show that the VSS signal goes to the VSSB, and the VSSB produces the two signals described above. The VSSB is calibrated to reflect the tire diameter and the rear axle ratio. The F-Body does not have a VSSB.

If you want to set it up like a B-Body, with a B-Body PCM, I am not familiar with that system.

http://www.tbichips.com/drac/VSSB%201.jpg

[Injuneer]

Here's a photo I took of a reluctor wheel on the pinion shaft of a 9-inch rear in low 8-second 97 F-Body. But it is used to measure transmission slip, feeding a MoTeC M800 ecu.