Rear Yoke question

[G Force]

I have a very small amount of play in the Rear yoke and th mechanic says it can cause a vibration. he reccomends I get a new Yoke for a 8 3/4 rear.  Where can I get this item?

[John_Kunkel]

What kind of play? Back and forth while turning or up-and-down/sideways? Any up-and-down/sideways play is bad, it will destroy the gears in short order.

It's unlikely the yoke, itself, is the source of the play. If the casting number on the housing ends in 489, there is a crush sleeve that can cause the nut on the yoke to loosen. If the casting number ends in 741 or 742, it might be possible to tighten the nut to eliminate the play. If the nut is tight and there is still play, the pinion bearings are probably shot. 

[Just 6T9 CHGR]

www.manciniracing.com has them

[phat69charger]

Well like John_Kunkel, stated which pinion do you have? Find out what you have then go from there, but here's some links to pinions on ebay and the mancini page:

http://store.yahoo.com/chucker54/axleyokekit.html

http://cgi.ebay.com/ebaymotors/Mopar-8-3-4-Yoke-Kit-Coarse-Spline-7260-Joint-NEW_W0QQitemZ8016412988QQcategoryZ33728QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Mopar-Course-10-Spline-Smal-U-joint-Yoke-8-75_W0QQitemZ8017787356QQcategoryZ33731QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[G Force]

What kind of play? Back and forth while turning or up-and-down/sideways? Any up-and-down/sideways play is bad, it will destroy the gears in short order.

It's unlikely the yoke, itself, is the source of the play. If the casting number on the housing ends in 489, there is a crush sleeve that can cause the nut on the yoke to loosen. If the casting number ends in 741 or 742, it might be possible to tighten the nut to eliminate the play. If the nut is tight and there is still play, the pinion bearings are probably shot.  

Sorry I did not discribe the problem acuratey.  The play is in the area of the yoke where the universal joint sets into not the part that sets on the spline.  The rear end I have on the car is casted 489 and the gears are new 3.91's.
It looks lime there is some wear in this area from previous worn out universal joints.

[Chryco Psycho]

ok so you still need a new yolk , & you need to know if it is the small or large U joint & if the gears you have are 10 spline or 29 spline before you order a new yolk , the nut size is different between the 2 splines , John has a reference for which size nut each spline count uses , the other problem is that the 489 carrier uses the crush sleeve so the nut has to be torque EXACTly correctly or the crush sleeve can   be damaged & it will need to be replaced as well   which is a lot more work

[firefighter3931]

There are two different u-joint sizes...7260 (small) and 7290 (large). There are 2 different pinion shaft spline counts as well....10 spline and 29 spline. You can determine the spline count externally w/o pulling the yoke by checking the pinion nut size.

If the pinion nut is 1 1/8in then you have a 10 spline yoke
If the pinion nut is 1 1/4 or 1 5/16 then it's a 29 spline yoke

As Chryco stated, the bearing preload is set with a collapsable crush sleeve so once it's loosened off a new sleeve should be installed to get the proper pre-load and avoid failure. A couple of companies make a solid spacer to replace the crush sleeve which is the weak point of 489 centersections. Personally, i'd upgrade to the solid spacer when it comes apart. Mopar performance sells the rear yokes individually and in kits with u-joints. They have a kit that adapts the small u-joint(7260) to the larger yoke (7290) and it comes with a conversion u-joint.

Basicly, you need to determine the u-joint size and spline count before ordering parts. Measure the width of the u-joint and get a socket on the pinion nut to determine the spline count using the reference sizes i posted above.

Ron

[G Force]

My car has 316 rear wheel HP (Mustang Dyno) And I now have the smaller U joints, should I be concerned about upgrading to larger U joints? Also does the solid spacer have any negative affects?
Thanks in advance!

[firefighter3931]

My car has 316 rear wheel HP (Mustang Dyno) And I now have the smaller U joints, should I be concerned about upgrading to larger U joints? Also does the solid spacer have any negative affects?
Thanks in advance!

No downside to the solid spacer...it just won't collapse like the crush spacer will. That is the weakpoint in a 489 case and the solid spacer corrects it ! Richmond and Ratech both carry the replacement spacers and shim kits. This will need to be installed by a tech with the right equipment to measure backlash on the ring and pinion.

As for the u-joints as long as they're in good shape and you're not running slicks on the car continuously....i don't see a problem. Automatic transmission cars aren't as hard on u-joints as stick cars. You still need to get a socket on the pinion nut and determine how many splines are on the pinion shaft. More than likely it'll be a 29 spline (most common) but you need to be sure. Once you have all the info i can help with part numbers.

Ron

[G Force]

Thank you All !

[Chryco Psycho]

welcome
BTW the Ratech spacer is part # 4103

[G Force]

Recieved the parts from Mancini racing today. Will install in the next week or so. Thanks again for the info!

[Rolling_Thunder]

yeah - i went through hell trying to find a 7290 style with the 10 splines...    got quotes $180 for a new one...    junkyard had one for $3...   getting it off was a chore though