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FS5W71B Input shaft interchange?

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Hey guys, I've got a FS5W71B that had the front counter shaft bearing failure.  Bearing cage took out some teeth on my 4th gear and input shaft.  Can't find a new set anywhere, but I can find new FS5W71C Input shaft/4th gear sets.  I understand the gears are wider, but by how much?  Will the FS5W71C Input shaft and 4th gear work with my "B" transmission? 

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This used one is the broken one, if so throw it away, a bearing cage didn't do that kind of damage, a bearing going thru the gears likely did that damage, and it is likely not all the damage that was done unless you have completely pulled it apart from one end to the other and looked at every single part.

 

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There is no 4th gear on any 4 or 5 speed. At least none with gear teeth. That's the counter shaft drive gear. They are a set and make the difference between wide, mid and close ratio transmissions so you need the one with the same number of teeth..

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49 minutes ago, wayno said:

This used one is the broken one, if so throw it away, a bearing cage didn't do that kind of damage, a bearing going thru the gears likely did that damage, and it is likely not all the damage that was done unless you have completely pulled it apart from one end to the other and looked at every single part.

 

Right, I took it apart and what’s pictured is the only damage that I found other than the failed front countershaft bearing.  My question was, would a “C” type input shaft and countershaft gear work with my “B” type transmission.

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39 minutes ago, datzenmike said:

There is no 4th gear on any 4 or 5 speed. At least none with gear teeth. That's the counter shaft drive gear. They are a set and make the difference between wide, mid and close ratio transmissions so you need the one with the same number of teeth..

Thank you for the info.

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I'm going to say no. There were a lot of changes in the 71C. For one, the gears are wider

 

 

Take it back if you can. This is why it was sold.

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25 minutes ago, datzenmike said:

I'm going to say no. There were a lot of changes in the 71C. For one, the gears are wider

 

 

Take it back if you can. This is why it was sold.

It was free.  I’m going to try and make it work with the 71C parts.  Not trying to rebuild it for any economical reason.  Just enjoy the challenge of learning and making stuff work.  I’ll post updates for future reference.

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Oh absolutely, give it a try! I was suggesting don't go out on a limb. I have an '85 diesel rear case on my '79 zx 5 speed. It gave me the reverse check sleeve (impossible to shift down from 5th into reverse) and taller shift ears so I could shorten the throw of the shifter. Had to try it.  

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How many teeth are on that gear,. I tried to count them but it is pretty chewed up, I have a 71B 4 speed, will them gears work, I will count teeth.

IwBq2Tv.jpg

Edited by wayno

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OK, I just counted teeth, the big gear has 32 teeth and the small gear has 21 teeth, is that what yours has?

 

010.jpg

 

012.jpg

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1 hour ago, wayno said:

How many teeth are on that gear,. I tried to count them but it is pretty chewed up, I have a 71B 4 speed, will them gears work, I will count teeth.

 

Mine is a 21/32 tooth.

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That is exactly the same count I got on the 71B 4spd, PM me/message me if your interested in them.

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1 hour ago, datzenmike said:

Oh absolutely, give it a try! I was suggesting don't go out on a limb. I have an '85 diesel rear case on my '79 zx 5 speed. It gave me the reverse check sleeve (impossible to shift down from 5th into reverse) and taller shift ears so I could shorten the throw of the shifter. Had to try it.  

 

Now that’s pretty slick.  

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2 minutes ago, wayno said:

That is exactly the same count I got on the 71B 4spd, PM me/message me if your interested in them.


I guess we’ll never know if the 71C input shaft/gear will work lol

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32/21 is for a wide ratio gearing. Is this from the '74? because this is what it had in it for a 4 speed. Had the extra low 3.592 first gear.

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The gears I counted teeth on were from a 71B 4 speed, the ones that have the plate/6 bolts just in front of the shifter, the tailshaft housing does not have the gussets around the bolts like on a pre 80 transmission, I have/collect these transmissions for the front L cases and bearing covers as they are getting harder to find every day.

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It wont work. You may be able to use whole 71c guts on a 71b mainshaft and use a 71b rear but you will have to do the 71b case mods to the front side to fit the c guts. The c guts are skinnier in the engagement/synchro area to make room for wider gears and pretty sure the shift forks are different. The later 71c’s have beefier shift forks than the earlier 71c’s

Edited by scooter

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The 71c is a better trans get yourself a d21 71c and do the front case mod. Depending  on which 71b you have you will have to mod your driveshaft but its probably better in the long run as they made them till 1998 and they are alot stronger

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