speedo ring and pinion question

[Farmer Joe]

Do you have to take the tailhousing off and switch the ring gear for the speedo if your changing the speedo drive pinion?

 

Wanted to see if i could use the red geared drive from my stock 77 3 speed auto over to an 80 720 5 speed... wanna try and get my speedo workin right if i can...

 

Thanks

[datzenmike]

The worm gear on the output shaft stays the same. The speedo pinion can be unbolted and removed easily and changed. There is a 10mm bolt holding a key that fits a slot in the pinion that positions it for correct engagement.

 

 

 

The pinion for the 510 auto or the 4 speed won't work in the FS5W71B in the 720 truck. You will need one from an '80 or newer 720, 200sx, 280zx (non turbo) or Maxima. Has to be '80 or newer.

 

.

[Farmer Joe]

its not a 510 auto that the red cog was from... my 77 kingcab had the stock 3 speed auto in it.. im takin the red cog from the 77 auto and puttin it in the 5 speed..

 

is the auto vs the manual the issue?

[darrel]

You can cut another slot opposite on the carrier. 3 spd auto and manual carrier they are the same diameter.

 

The 4 spd auto carrier is a larger diameter

[datzenmike]

The auto and standard are different I believe, but will check tonight. A '77 would never fit an '80 anyway. The cut for the key is 180 different.

 

The 4 speed auto wasn't around these years anyway.

[datzenmike]

The pinion numbers are different. Even the 20 tooth red cogs are different numbers.

 

The 720 came with many tire/gear ratios and the standards used 16, 17, 18, 19, 20 and 22 toothed pinions