Question about yoke for 8 3/4" 489 case rear end.

[1968_Satellite]

I have a mopar 8 3/4" 489 case differential from a Duster Twister and need to get a replacement yoke for it, someone broke the ears on one side and ran bolts through it and the car vibrates around 55mph.. it takes the 7260 small u joints. I was told theres two different types a 10 spline and 29 spline yoke. Is this true and which is the more common/more likely one?

 

[65CopCar]

I have a mopar 8 3/4" 489 case differential from a Duster Twister and need to get a replacement yoke for it, someone broke the ears on one side and ran bolts through it and the car vibrates around 55mph.. it takes the 7260 small u joints. I was told theres two different types a 10 spline and 29 spline yoke. Is this true and which is the more common/more likely one?

Its a crap shoot. Believe most of the original were 10 spline and the aftermarket were typically 29 spline in my experience. But you need to check to know for sure.

 

[33 IMP]

basically four yokes for passenger rears.
Big joint, fine spline
Big joint, coarse spline
Small joint,, fine spline
Small joint, coarse spline.
Only way to know what you need ,for SURE, is to pull your yoke off.
And since a 489 (stock) uses a crush sleeve.... pulling the yoke off might disturb the gear set-up.

 

[davek]

8 3/4 axle info good read.

 

[1968_Satellite]

basically four yokes for passenger rears.
Big joint, fine spline
Big joint, coarse spline
Small joint,, fine spline
Small joint, coarse spline.
Only way to know what you need ,for SURE, is to pull your yoke off.
And since a 489 (stock) uses a crush sleeve.... pulling the yoke off might disturb the gear set-up.

Thats why I didnt want to disturb it. Lol. Guess ill put a wanted ad up for both snd then ill have the one I need and can sell the one I dont

 

[1968_Satellite]

8 3/4 axle info good read.

Thanks

 

[Vaanth]

I have a mopar 8 3/4" 489 case differential from a Duster Twister and need to get a replacement yoke for it, someone broke the ears on one side and ran bolts through it and the car vibrates around 55mph.. it takes the 7260 small u joints. I was told theres two different types a 10 spline and 29 spline yoke. Is this true and which is the more common/more likely one?Original "489" differential yokes were fine spline.

The original pinion and yoke in the "489" differential was a fine spline with 29 splines.

NOTE: During the phase-in period of 1969 - 1971 for the "489" unit, there were several permutations of pinion size and yoke availability.
1969 - 1970 '489' units may be equipped with a coarse (10) spline pinion, particularly for the large 7290 universal joint and the 1-3/4" pinion which also appeared in some "489" carriers during this period

8 3/4 axle info good read.

The information in that post is useful but is incomplete. It was taken from my original document and adjusted some. That has happened many times over the years though. The document is a reference guide, not a how-to, much like my Thermo-Quad guide.

The original document needs some correction, updating, and to be written better. I have started updating it, but it is a low priority.

The complete original document will not fit in a single post, but if interested to see the original, full document, as it was written in 1999, visit the following link:

A Chrysler 8-3/4" Rear Axle Guide

FYI...

 

[ckessel]

I have a 489 in the wagon. According to Doc Diff, if the pinion nut is 1.25" or bigger, it's a 29 spline. Same seal regardless. You have a 50/50 chance of having a crush sleeve or the solid spacer if someone was in it before. I'm in that boat. My pinion seal is leaking, so I'm going to get the solid spacer and just be done with it.

 

[1968_Satellite]

Can I ask a "silly" question? Why the hell would Chrysler make a 10 spline and a 29 spline yoke? Why not just pick one and stick with it instead it having two different splines for the same exact application?

 

[1968_Satellite]

The original pinion and yoke in the "489" differential was a fine spline with 29 splines.



The information in that post is useful but is incomplete. It was taken from my original document and adjusted some. That has happened many times over the years though. The document is a reference guide, not a how-to, much like my Thermo-Quad guide.

The original document needs some correction, updating, and to be written better. I have started updating it, but it is a low priority.

The complete original document will not fit in a single post, but if interested to see the original, full document, as it was written in 1999, visit the following link:

A Chrysler 8-3/4" Rear Axle Guide

FYI...

Man! Thanks for helping me out! Im sure thats what it has then since the rear end was never touched

 

[davek]

Can I ask a "silly" question? Why the hell would Chrysler make a 10 spline and a 29 spline yoke? Why not just pick one and stick with it instead it having two different splines for the same exact application?

Because in 1970 they were smoking the good stuff. 1970 one year only crap. They were smokin.

 

[1968_Satellite]

I have a 489 in the wagon. According to Doc Diff, if the pinion nut is 1.25" or bigger, it's a 29 spline. Same seal regardless. You have a 50/50 chance of having a crush sleeve or the solid spacer if someone was in it before. I'm in that boat. My pinion seal is leaking, so I'm going to get the solid spacer and just be done with it.

Thanks for the valuable info. Thankfully my seal isnt leaking,but it has a pesky vibration at 50-55 which i am attributing to the fact one side of the yokes ears were damaged and now it has longer bolts and nuts running through the ears on one side. I replaced the u joints so those are all new and fine.
I was scared to pull the yoke because I drive the car to work (side streets not freeway) and didn't want ti screw it uo because of the crush sleeve pre load. I've read though that there's a way to remove it and tighten it back up and have it be ok.

 

[ckessel]

Gotta keep family members employed.

 

[1968_Satellite]

Because in 1970 they were smoking the good stuff. 1970 one year only crap. They were smokin. View attachment 1963578

That also must explain the hit or miss build quality. Lol

 

[Vaanth]

I have a mopar 8 3/4" 489 case differential from a Duster Twister and need to get a replacement yoke for it, someone broke the ears on one side and ran bolts through it and the car vibrates around 55mph.. it takes the 7260 small u joints.

Vibration effects due to imbalance are less toward the ends of the driveshaft, but enough imbalance in that yoke due to the bolts on one side might show up as a vibration. To temporarily "balance" the shaft to determine if that might be the problem area, use hose clamps as shown in the following image to offset the bolts' weight.

Add the screw side of the clamps(s) opposite the bolts in the yoke. It might not be perfect because you cannot be directly opposite the bolts weight, but it might lessen the vibration.

 

[davek]

wasnt there a tread that said if a certain size nut on yolk told what spline count it was?

 

[davek]

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/131186/re-what-size-nut-on-8-3-4-pinion-yoke.html

 

[1968_Satellite]

Vibration effects due to imbalance are less toward the ends of the driveshaft, but enough imbalance in that yoke due to the bolts on one side might show up as a vibration. To temporarily "balance" the shaft to determine if that might be the problem area, use hose clamps as shown in the following image to offset the bolts' weight.

View attachment 1963593

Add the screw side of the clamps(s) opposite the bolts in the yoke. It might not be perfect because you cannot be directly opposite the bolts weight, but it might lessen the vibration.

Thanks for the suggestion. I had thought of trying that,but wasnt sure if it would work. Worth a shot. All the original weights are on the driveshaft and both front and rear u joints are new.

 

[1968_Satellite]

wasnt there a tread that said if a certain size nut on yolk told what spline count it was?

Nice 1970 Dodge. Always liked the front ends on them

 

[coloradodave]

wasnt there a tread that said if a certain size nut on yolk told what spline count it was?

Post #8 here...^^^^^^^^^