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Old 01-15-2015, 08:52 AM   #1
Bjj_junkie
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buy new transmission but don't understand gear ratios

hey everyone, after doing as much research as i can and talking to the few people i know that know some about the subject. i concluded that ill buy the same transmission i have in the truck now just rebuilt from a site. i have a 72 step side with a 250 and 3 speed floor shifter. the transmission is no good as it is and it seems to cost more to get it rebuilt. I'm not sure if its a muncie or saginaw but ill find out once we pull it out. after looking online for some time i finally found a site that sells both muncie and saginaw rebuilt 3 speeds but theres 5 different gear ratio options and i have no idea which would be the one i need. If anyone could help me understand this a bit more and recommend which would be best for a daily driver that would be awesome.

they start at 254-150 and go up to 351-189

heres the site I'm talking about if you can make sure this is the transmission ill even need because i see the site is strictly racing so I'm not %100 sure this is even what ill need http://www.smileysracing.com/shopping/?ic=1574

thanks a bunch
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Old 01-15-2015, 09:14 AM   #2
Lattimer
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Re: buy new transmission but don't understand gear ratios

The numbers they are giving you are the first and second gear ratio. So 1st is 2.54:1, second is 1.50:1, and 3rd will always be 1:1.

The higher number is a lower gear, so that 3.51:1 1st gear will be really low, and you'll need to shift out of first before you get moving very fast.

That being said----those transmissions are stock units rebuilt for circle track racing. Its not the direction I would go. I can't imagine that you couldn't get your trans rebuilt cheaper with stock parts. The 3-speeds are pretty simple. Usually they need a couple of bearings, new synchros and seals.

Whats going on with the trans you have?
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Old 01-15-2015, 09:25 AM   #3
Bjj_junkie
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Re: buy new transmission but don't understand gear ratios

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Originally Posted by Lattimer View Post
The numbers they are giving you are the first and second gear ratio. So 1st is 2.54:1, second is 1.50:1, and 3rd will always be 1:1.

The higher number is a lower gear, so that 3.51:1 1st gear will be really low, and you'll need to shift out of first before you get moving very fast.

That being said----those transmissions are stock units rebuilt for circle track racing. Its not the direction I would go. I can't imagine that you couldn't get your trans rebuilt cheaper with stock parts. The 3-speeds are pretty simple. Usually they need a couple of bearings, new synchros and seals.

Whats going on with the trans you have?
yeah thats what i was thinking but i can't seem to find anyone else that sells them. and as for getting it rebuilt, I've called most local places i can find online and they either don't do them or couldn't give me a straight number just anything ranging from 600 - 1700. and I'm not too sure whats wrong with it, I'm new to all this and learning as i go but it doesn't seem to fall into gear. we only drove it for a few mins around the storage after the tow truck dropped it off but it just felt loose and wouldn't grab first very well.
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Old 01-15-2015, 02:53 PM   #4
Fitz
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Re: buy new transmission but don't understand gear ratios

Quote:
Originally Posted by Bjj_junkie View Post
hey everyone, after doing as much research as i can and talking to the few people i know that know some about the subject. i concluded that ill buy the same transmission i have in the truck now just rebuilt from a site. i have a 72 step side with a 250 and 3 speed floor shifter. the transmission is no good as it is and it seems to cost more to get it rebuilt. I'm not sure if its a muncie or saginaw but ill find out once we pull it out. after looking online for some time i finally found a site that sells both muncie and saginaw rebuilt 3 speeds but theres 5 different gear ratio options and i have no idea which would be the one i need. If anyone could help me understand this a bit more and recommend which would be best for a daily driver that would be awesome.

they start at 254-150 and go up to 351-189

heres the site I'm talking about if you can make sure this is the transmission ill even need because i see the site is strictly racing so I'm not %100 sure this is even what ill need http://www.smileysracing.com/shopping/?ic=1574

thanks a bunch
The GrimJeeper has a great final drive ratio calculator on line. Choose the trans you want (gear ratios are built in ) or specify your own trans ratios, pick a rear axle ratio and tire size and it will tell you RPM vs MPH in any gear or RPM at any speed in any gear. That way you can see just how the tires and transmission choices affect engine RPM.

http://www.grimmjeeper.com/gears.html
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Old 01-15-2015, 02:59 PM   #5
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Re: buy new transmission but don't understand gear ratios

Quote:
Originally Posted by Bjj_junkie View Post
yeah thats what i was thinking but i can't seem to find anyone else that sells them. and as for getting it rebuilt, I've called most local places i can find online and they either don't do them or couldn't give me a straight number just anything ranging from 600 - 1700. and I'm not too sure whats wrong with it, I'm new to all this and learning as i go but it doesn't seem to fall into gear. we only drove it for a few mins around the storage after the tow truck dropped it off but it just felt loose and wouldn't grab first very well.
If its still a column shift, it may be the shift linkage is hanging up/not adjusted and have nothing to do with the actual transmission.
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My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881
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Old 01-15-2015, 03:10 PM   #6
67 cst swb
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Re: buy new transmission but don't understand gear ratios

That could be a clutch adjustment or other easy fix.
It is difficult for a shop to give a rebuilding price over the phone.
This is because a lot of internal parts are reused on a Manual Transmission.
Such as gears, shafts, etc... but if any of these are broke, worn, or missing (as in a trans brought into a shop in a box) then things can start adding up.

I would maybe take the vehicle as is to a mechanic (not Goodyear or Meineke, etc...) for them to look at. A reputable Mechanic can determine if its a clutch issue or an internal transmission issue.
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Old 01-15-2015, 07:27 PM   #7
Bjj_junkie
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Re: buy new transmission but don't understand gear ratios

Quote:
Originally Posted by 67 cst swb View Post
That could be a clutch adjustment or other easy fix.
It is difficult for a shop to give a rebuilding price over the phone.
This is because a lot of internal parts are reused on a Manual Transmission.
Such as gears, shafts, etc... but if any of these are broke, worn, or missing (as in a trans brought into a shop in a box) then things can start adding up.

I would maybe take the vehicle as is to a mechanic (not Goodyear or Meineke, etc...) for them to look at. A reputable Mechanic can determine if its a clutch issue or an internal transmission issue.
Thank you, thing is it's not registered at the moment so every time we move it it's about a 100 bucks to tow it around. But if nothing else that might be my only option
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