73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Sprinkler-Man on June 29, 2014, 07:31:58 pm
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When I bought the truck the speedo cable didn't work. I replaced the cable but when I screwed it into the adapter on the transfer case it still didn't work. The shaft on the adapter is broke so I got another one but the shaft on the new adapter will not fully go into the steering gear shaft. The speedometer cable will not screw in directly into the transfer case either. I took the steering gear shaft out and nothing appears to have broken off in it. Anyone else run into this? Is the speedo cable or adapter year specific?
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The "shaft" on the adapter should be a key that pulls out, so that when it breaks it doesn't destroy the adapter. Measure the diameter of the key with the tang on it that goes into the adapter. My bet is that you need a .152 tang to .104 square-drive key between the stock ACDelco adapter and the NP203 or NP205 transfer case. The square-drive key needs to be the long one. BTDT, just last week.
Call Texas Industrial Electric and order an HR124. $9.90 and $5.05 Priority Mail shipping. No internet ordering, just give them a call. Ask for Stephanie to take your order. I ordered Thursday mid-day, the order went out the next day, and I had it Monday.
If you need a different size key, you should be able to find it here. I think they have darned near any combination.
http://www.texasindustrialelectric.com/90_Degree_Transmission_Adapter.asp
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Thanks, I will give that a try. Any idea why the speedo cable won't screw in directly.
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The square drive key needs to be long, and the factory parts book shows my 78 delivered from the factory with the adapter. The standard cable length may not be enough. I think one cable was used for both C and K trucks. The cable on the C did the big round corner into the tranny, the cable on the K went straight instead, and into the 90-degree adapter. The transfer case may need a longer cable than the tranny if you were going to plug it straight in.
Bear in mind, on mine, the 90-degree adapter was also a gear step-up (opposite of reduction) for the gauge to read correct speed. On the original ACDelco adapters, the step up ratio is stamped on the flat opposite the cable connection.