NP208 & NP241 dimensions the same?

[Russell]

I've got an SM465 / NP208 combo I just recently picked up for my truck. While there is nothing wrong with the 208, I eventually plan to swap over to a new fuel injected engine which all require a VSS.

Since the 208 never came with one, and VSS 205s are really tough to find, I picked up a 32 spline NP241 about 6 months ago or so that came with a speedo cable drive on it already, and a toner ring setup for when the time comes to make the switch.

I did some quick searching which turned up the result that NP241s and NP208s share the same dimensions, adapter, and spline counts on both the input shaft, and the slip yolk output. Is that correct?

 

[JEBSR]

My 87 is fuel injected with no speed sensor on my 208. The 87's didn't use them on the t/c. Now if you disconnect the speedo cable it will spit out a VSS code. I believe there is a sensor on the gauge cluster on mine that converts and sends the signal.

 

[lectric80]

Jebsr is correct, on the early chev's there is a small VSS that reads the vehicle speed by bouncing a IR signal off the back of the speedo arms. Don't know the exact years on the K5's that this was used on.

 

[Russell]

Those are good for TBI engines, but not so much for Gen III 5.3Ls, 6.0Ls etc The old style speed sensors are bolted onto the back of the speedometer head, and provide a 2000 pulse per mile signal that the old TBI, and TPI ECMs use.

The 40 tooth toner ring is a totally different animal. It doesn't pulse, but generates a varying voltage in the sensor from 0 - 100 some volts, which is used by the 90 - to current trucks. In 90 - 96ish, the trucks have a little box called a DRAC which converts the toner ring signal over to the 4000 pulse per mile signal the speedometer uses, 2000 pulse per mile the ECM or PCM uses, and to whatever signal the ABS needs.

When the Vortec V8 engines were introduced along with the 90 + TPI / LT1 etc engines in the F-bodies / Corvette, the ECMs and PCMs started taking that toner ring voltage and interally sorted out the various signals. The newer trucks have their speedometers, tachs and cruise attached to the PCM for their signals, which is what I intend to do as well.

 

[gmc4cw]

I did some quick searching which turned up the result that NP241s and NP208s share the same dimensions, adapter, and spline counts on both the input shaft, and the slip yolk output. Is that correct?

I swapped a 241 in to my truck. everything is exactly the same when it comes to hooking it up. I know the insides are different slightly. But if you had one of each laying on the ground, it would be hard to tell which was which without the tag and being really knowledgeable about t-cases.

 

[Russell]

Awesome

Thanks guys!