LTX and LSX Putting LT1s, LS1s, and their variants into Third Gens is becoming more popular. This board is for those who are doing and have done the swaps so they can discuss all of their technical aspects including repairs, swap info, and performance upgrades.

quik questions - LT1 T56 VSS & speedometer

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Old 05-08-2012, 09:02 AM
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quik questions - LT1 T56 VSS & speedometer

Will the 95 lt1 pcm and t56 play well with the stock 92 camaro speedo? Or do I need a dakota box?
Old 05-08-2012, 01:51 PM
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Car: 82 Berlinetta/57 Bel Air
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Need someone to verify this, but I believe the PCM speedometer output is 4000 ppm like the 3rd gen speedometer.
Old 05-08-2012, 03:33 PM
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Re: quik questions - LT1 T56 VSS & speedometer

Originally Posted by five7kid
Need someone to verify this, but I believe the PCM speedometer output is 4000 ppm like the 3rd gen speedometer.
ok thanks five7, you gave me an additional term to search for.. i searched lt1 ppm and found the answer from pocket.

Missed that part

All 3rd gen electric speedos that Ive seen require 4,000 PPM input. The best I can tell is LS1s use a 40 pulse per revolution input and change it to 4,000 PPM output to the speedo. The cruise output is 2,000PPM just like 3rd gen cruise

Regardless of older 3rd gens using a 2,000 or 4,000 PPM signal, the value can easily be changed when tuning the LS1 PCM to make what you have work

The dakota box is used to change LT1 T56 11/17 pulse per revolution signal to 2,000/4,000PPM 3rd gen signal when keeping the TPI
So since I am using the lt1/t56 combo and not tpi I should be ok at 4000 pulse per min
Old 05-08-2012, 03:55 PM
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Well, now that I see pocket's post again, it may not be correct. Actually sounds like the LT1 output needs to be converted.

With all of the LT1 swaps that have been done, I would think the answer would be easier to find. I have no personal experience to relate, however.
Old 05-11-2012, 11:01 PM
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Re: quik questions - LT1 T56 VSS & speedometer

Yes it will work directly without a converter.

You will have to splice the output from the pcm directly to the wire from the buffer box->instrument panel if its a TBI car.
Old 05-11-2012, 11:31 PM
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Re: quik questions - LT1 T56 VSS & speedometer

I'm not sure about the 94+ T56's, but the 93' T56 with its 11ppr ratio does kind of work with the thirdgen electric speedo.

Its about 6% high at all speeds. At an indicated 80mph I'm doing 75mph.
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