1972 th400 speedo error, help?
 

Been awhile since I been on here but you always help so if anyone has input that would be great... I have a 72 c10 with 402 engine and a turbo 400 trans... Speedo used to work then the speedo gear housing broke so I ziptied it up to get it to work now it don't work again and I think I may of last some gizmos and gadgets.. Tires are 31x10.50r15 I believe.. And gear ratio is 3:08. I know that's how you change speedo but here's a pic of what I have its off google but I would need the housing, the driven and drive gear and all
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Re: 1972 th400 speedo error, help?
 

Also, I have no dash lights. And only gauge that works is my oil pressure due to it being fluid driven I know.. And speedo is not working due to the issue listed above... I'm thinking I need to order a printed circuit board for the cluster since its original that's 40 some years old.. Am I correct? All the bulbs looks good just missing one bulb and one holder for it... Thoughts???

Re: 1972 th400 speedo error, help?
 

I may be able to come up with that adapter. i will check tomorrow and let you know.

Re: 1972 th400 speedo error, help?
 

I just bought drive and driven gears off of eBay for my th400. You can get the housing too on there. There's plenty of online calculators that'll get you close on the number of teeth you need.

Re: 1972 th400 speedo error, help?
 

http://www.transmissioncenter.net/sp...n_______va.htm Go down the page a little ways, they sell them if the boys can't help you out...

Re: 1972 th400 speedo error, help?
 

Looks like to find out what driven gear you need, you will need to know what drive gear you have, and also the number of revolutions the speedo cable must turn to register one mile on the odometer.

Re: 1972 th400 speedo error, help?
 

Tim, did you try connecting the speedo cable directly to the transmission? Try that and see if the speedometer works at all. If so, get a free gps speed app for your phone and see how far off it is. You may not need the adapter. When I bought my TH400 it had an adapter on it that was broken. I did not use it when I put the transmission in, and my speedo is slow by 3 mph per a gps app that I have on my phone. I have 3.73 gears though.

Re: 1972 th400 speedo error, help?
 

There are also going to be numbers on the side of the adapter that give the ratio percentage difference

Re: 1972 th400 speedo error, help?
 

Never knew any of that!! Thanks guys will do that this weekend!!! You guys are awesome thanks again y'all, I knew I could always get info here

Re: 1972 th400 speedo error, help?
 

Got it all fixed