To all the 1953-54 chevy car guys: I want to use my original working speedometer gauge but I believe my original speedometer cable will not match up to my 350 Turbo transmission. It does not work when I attach them together! Un attached, I spin the cable end, the speedometer registers. What type of speedometer cable do I need, that works with a 53 gauge with a 350 tranny? Should I run a different after market gauge? If so, what type of bolt on application do you recommend? On a side note, my gear ratio is no longer 4:11 it is now 3:08 because I have a nova rear end. I heard you have to take that into account, I could be wrong?
You may need a speedometer correction gear ratio adapter. This small gearbox adapter screws on to the transmission speedometer drive with the cable screwing on to the small gearbox adapter output. Thread size is standard 7/8-18 as used on all cable driven GM and most other cars and trucks with screw on cable at transmission. They come in several differant gearbox ratios. If it is a .72. In other words cable speed will be reduced by 28 percent and speed and distance readings on speedometer will be reduced by the same amount. As an example if your speedometer shows 60 mph, installing this ratio adapter will bring the indicated speed down to 43 mph. This is often the only way to correct a speedometer in which the rear axle ratio has been changed thus throwing off the speedometer accuracy. Changing the gears in the trans is usually not the solution since gears are usually not available when a large rear axle gear is installed. If your speedo was accurate with the original rear axle and is now reading high with your new big gear axle this adapter may be your solution. Merely divide your new gear ratio into the old ratio to see if this is the adapter you need. An answer of .7 to .74 is usually close enough. For example if you had a 3.00 axle and now have a 4.11 merely divide 4.11 into 3 = .72 ratio adapter. Another simple method is to have someone with an accurate speedo follow you and then multiply your indicated speed by .72 and see if the answer comes close to the actual speed
If I remember correctly the original cable worked fine on my '50. The easiest way to correct the speed is as mentioned above.
Put a TH350/ 10 bolt in my buddys 235 powered 54. Plugged the original cable in and it works fine. And is pretty accurate... Do not believe an adapter is needed..
Mine was a little slow with a 3.42 and short tires, read 65 keeping up with traffic. then it made noise and then it died.
Um... no. That's so wrong I'm not even sure where to begin. But I'll try: Since most transmissions were available in most vehicles the OEs manufactured, there is a factory solution for ever trans/rear gear/tire combination. You said speedo gears usually aren't available when a large rear axle gear is installed. Except in trucks. And passenger cars with high-perf axle combos. If you've got a TH350, you can make it work with factory parts. You just need the right tailshaft drive gear and the proper factory housing to put it in. My '62 Suburban came from the factory with a granny 4spd, 3.90 rear gears and I-don't-know what tires. I've swapped in an orphan New Process 833 4spd OD, 3.42 gears and new tires. I did the math, did some checking and figured out what drive gear I needed with that combination, and my odometer is absolutely dead accurate to the tenth of a mile, and my restored speedometer is exactly accurate too. Go to this site: http://www.transmissioncenter.net/speedometer_calibration_______va.htm Good prices on the parts you need. There will be calculators there that tell you what drive gear you need with which rear gears and tire sizes. They'll also tell you what gear housing you need for the transmission tailshaft. They have different numbers on them, like one will be for 41, 42, 43 and 44 for the "blue" drive gear. Call them, and they'll walk you through it. As for the speedo itself, they almost never go out of calibration, but they very often do break. The lubricant in the speedo head goes bad, and parts break. Like someone posted: "It made noise, then it broke." Every old car I've had has done that. A good friend of mine own AutoInstruments, and I've done several gauge restoration stories with him. http://www.autoinstruments.com/ He's a stand-up guy, and won't charge you for stuff your cluster doesn't need. If you just want it mechanically fixed, but not cosmetically restored, he'll do it. If you want it concours restored, he'll do it. If your speedo starts making noise and behaving erratically, disconnect it immediately. It'll save you money. Trust me! Every old car I own ended up with a dead speedo in two weeks of driving it. Gentry has fixed them all. -Brad
In my 40 pickup with 3:00 rear end and 350th and 28" tall rear tires, I just could not get the right tooth count at trany and had went to the end of the tooth count scale available. My only option was a gear ratio adapter and got it to with in 1.2mph.
I'm thinking if your cable doesn't turn when hooking it to trans...you may have a stripped gear in the trans...take the driven gear out (where the cable hooks on) and check the teeth then maybe feel inside if you can feel the drive gear..(these things are plastic or nylon)...if there is a problem with either of these gears an adapter won't fix that....the 53 cable should work in GM 350....may read wrong BUT should turn the speedo head
I actually am not sure of the ratio of the rear end that went in it. I put in what he got for me. It was a 235/ powerslide car. I do think it is in the low 3.00 somewhere. I was speaking from the stand point that the stock cable went into the TH350 and the speedometer worked fine. I just drove by one of those "how fast are you going" things in town and it told me about the same as what the speedo said... 65-70 on the freeway and I am cruising along with everybody else, with plenty more to go... There was no scientific analysis, and I do not want anyone to be misled in anyway...
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