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5 speed transmission question


ronnny

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Ok sorry if I should of read this somewhere and missed it.

 

I have a 84 720 4x4 with a bad transmission.  The main shaft is broken.  It has a FS5W71b in the short length of 26.5 and goes to the divorced t-case.  I have found a FS5W71c transmission on craigslist. It is said to be from a 97 hard body.  I read the guide that I think Datsun Mike had put up in the past.  It says on like page 17 that the c has a larger main shaft and has a bigger driveshaft diameter than the b if I read it right.  But of course I am not sure about this and some of you would know.  I know the transmission is longer and I am able to shorten the intermediate drive shaft between the tranny and t-case. I was just wonder if the slip yoke is the same from the b to the c or if it is different?  It is a long way to go get this and do not want to drive 1.5 hours to find out the tail shaft is a different size and will not work.

 

The front case and bearings of my transmission are good like someone had been in it before.  The truck has 225k on it

 

Thanks

Ronny

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The FS5W71C from the S13/14 is much longer at 33+" but the D21 is around 31 or so, haven't really measured one myself.  The driveshaft for all 4 cylinder should be the same spline diameter but V6 'might' be larger.

 

The '97 Hardbody 5 speed will only work if it's from a KA engine and 2wd.... you will need to shorten the driveshaft to match and likely modify the transmission mounting point. Further the 71C transmission will have a closer ratio set of forward gears. This will increase your crawl speed (usually important in a 4x4)

 

720 4x4 71B ratios

 

3.592*

2.246

1.425

1.000

0.882

 

Hardbody 71C ratios

 

3.321*

1.902

1.308

1.000

0.833

 

* the difference is an 8% drop in MPH /  RPMs in low or high range. Forth and fifth gear would be the same.

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It is suppose to be from the ka24i motor.  I know on measurements others have gave me that it seemed to be like 30" long between the 2 lengths of the 71b transmissions.  My main thing is that My slip yoke from the old tranny fits the new to me tranny.  I can shorten or lengthen a shaft easy enough.  That is free except for time and work.  If I had to buy a yoke that would cost more dollars that I do not have.  Moving the mount is easy enough to do to.  I would even be happy with a 4 speed if I had it cause the 5th gear is useless in these under powered trucks with bigger tires.

 

Thanks for the information

Ronny 

 

Lower gear ratios are numerically higher so the hard body transmission is not geared with lower gears than the 720 4x4.  I know at a quick look I would say the same thing.

 

Thanks again

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Lower gear ratios are numerically higher so the hard body transmission is not geared with lower gears than the 720 4x4.  I know at a quick look I would say the same thing.

 

Thanks again

 

 

The 720 first gear will crawl slower than the Hardbody first gear. (taller, lower, shorter I don't know what it's called)

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