Tried searching couldn't find .swapping to 350 turbo in 55 chevy. New turbo has blue speedometer gear inside ******. What all do I need to convert, does power glide housing fit 350? cable? which gear color if blue inside ******?
I think your existing Speedo cable should work with TH350. Confirm? If that works, subsequent step will be to get it to read close to actual after it is running down the road.
I am not sure the gears were color coded in an Iron Powerglide. What truly matters is the tooth count on each of the two gears, and thus the ratio between them. What the speedometer measures is driveshaft RPM, so if you didn't change the rear end gears, or the rear tire diameter, that speed is the same, at any given speed, regardless of which model of transmission. The gear on the transmission output shaft is called the speedometer drive gear. The one that meshes with that, and that turns the speedometer cable is called the speedometer driven gear. Having the terms will help with the search. Counting the teeth on the driven gear is easy. On the drive gear, they are angled. You count the sides of those. Here is a good article: https://www.hotrod.com/articles/calibrate-gm-mechanical-speedometers/ That shows an orange drive gear marked with yellow dots, where you count the teeth. A blue drive gear on a TH350 has 10-teeth. If you go to any search engine, and search the internet for: TH350 speedometer gears, you now know what to look for.
If you partake of that auction site:. https://www.ebay.com/itm/132711077999 If not, that at least shows you the involved parts, colors, and tooth counts.
The stem on the Powerglide speedometer driven gear is longer than the TH350 gear so you can not use it. Start with a 20 tooth driven gear, its in the middle of the gear range. Run the car on a measured mile and see how many 1/10's your turning in a mile. IE if you are turning 11/10's in a mile your 10% fast, the TH350 gear is 5% per tooth so if you went to a 22 tooth that would slow you down 10% and put you back at 10/10's in a mile. If its to far off you will need a gear ratio adapter to correct it( that is if you don't want to tear into the ****** to replace the drive gear)I can make you up a ratio adapter if needed just let me know how many 1/10's your turning in a mile.
If the car is put together now, go for a drive and see how many percent the odometer is off, like he said. If the car is not put together yet and you can still easily get to the drive gear on the output shaft, count the teeth, do the calculation to figure out what driven gear you need to work with that, and your tire size and rear end gear ratio, as in the posts before the one above. Then get that gear, or if one is not available, you'll need to change both gears to get it to work.
OK Probably in the spring, I'm northern MN , winter coming on cars up on blocks with ****** and rear end ***embly out. Getting ready to install ****** then rear end, plus have new wiring harness to put in. So my winter is planned.
Thanks, will save this all this information . Found a kit for 350/ powerglide with bullet and gears 17,18,19,20,21,22
Thanks will keep your contact, probably got ahead of myself car won't be on the road until spring being I'M northern mn, Wanted to do everything that I could before installing transmission
The cars not put together as far as rear end and transmission, have a new 9" rear end 3.50 I'm installing along with the 350 transmission. Rear tires will stay the same.
Avoid using the 17 tooth gear, it was mainly used on Pontiac's with a larger drive gear in the trans, if you use it with a standard TH350 drive gear it will strip and possibly damage your drive gear.
After some thought I contacted the company I bought the new 350 transmission from. They asked my rear end gear ratio and tire size. Said a 23 teeth size was what I needed. I ordered it and will go from there, it will give me a starting point if its not right.
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