I.D.'ing Course vs. Corse Spline Yoke

[70 Cuda 340]

Are there any EXTERNAL indicators on the yoke to tell me if I have a fine (29) or course (10) spline drive pinion in a '70 489 rear-end? It's a long sorted story, but the short version is I want to order a new ring and pinion for my 489 rear, but don't know if I need a fine or course set-up. Someone is doing the work for me and I'd like to have the right part on hand when I drop the car vs. having the car sit in the shop waiting for a part to arrive. 

Any clues?

[MEK-Dangerfield]

Hello,

  And welcome aboard here.  You have asked a good question. I have a 70 with a 489, but unfortunately, I can't help you. Great question though. I'm sure someone will be along shortly to help you.

  Mike

[tactransman]

The only way I know to tell is to take the pinion nut off and look at the splines . You can tell without taking the yoke off. If you are getting it rebuilt any way , zip the nut off and look at it and then tighten it back up.Unless it is an older pumpkin it will most likely be 29 spline.

[Chryco Psycho]

where are the measurements 
 10 spline has asmaller nut , I think 1 1/4 , 29 spine is 1 5/16

[70 Cuda 340]

Hey Chryco, are you saying the pinion nut size is in fact an external indicator that can be relied upon, i.e. 10 spline  1 1/4 , 29 spine 1 5/16?

[tactransman]

I wouldn't trust the nut size because I had a guy do a rear end for me along time ago and he needed a different nut for the after market gears and he found one in his "goody" drawer .He could not tell me what it was off of.

[Chryco Psycho]

yup , the nut size isd different

[70 Cuda 340]

Pardon my ignorance, by I haven't spent much time outside the engine comparment on this, or any other mopar for that matter. Is the nut we're referring to accessible on the outside of the case without having to dismantle anything? (I'm hoping you say yes )

Thanks again for your help.

Dan

[tactransman]

It is the one that holds the yoke on the pinion shaft.(in the middle of the rear end yoke)

[Chryco Psycho]

you will have to unbolt the driveshaft  , I found the nut , the 10 spline is 1 1/8 " , the 29 spline must be 1 1/4 or bigger

[tactransman]

yup , the nut size isd different

 Duh , you mean the tread size of the nut. I thought you were talking about the socket size.

[Chryco Psycho]

yes the socket size
 , 10 spline is smaller at 1 1/8 "