7260 big enough???

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moparman111

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Hi, building a 8.75 for my all steel bodied 67 Barracuda street bruiser once it comes back from body/paint. The car will have a stout 440 with a 4spd coming back to an 8.75 filled with a 489 cased sure grip and 3.91 gears. I purchased the rebuilt 489 off a fellow member on here. It has a 7260 series yoke on it. I was told the 440 has around 450hp. Enough to propel an all steel body Duster with 4.10's, slicks, and a 4200 stall the Duster went 11.8 at 112. Now I am not going to be bracket racing my car but it will see Mason Dixon drag way once I get the car finished. It will get driven like a 440/4spd A-body should on the street. Any way can one of you with more knowledge than I chime in if I should buy a 7290, 1350, or I would be fine with the little 7260? As always all information is greatly appreciated:)

Robert
 
Guys thanks for your info. I know a 7260 might last as long as I am not trying to launch at every light. I figure since I will have to buy a new drive shaft that I would step up to a larger yoke/u-joint. Anyone know a good place to buy one at a great price? Are the strap versions stronger?
 
If you go 1350 there will never be a need to upgrade. I am using 1410s on my rat truck.
 
If I was buyin a driveshaft anyway then i would upgrade to bigger joints. My 366 spit a couple of those 7260s out, with 295/50s,a 3.55 X 3.09low, and no traction devices other than the pinion snubber.
My 1350s are still going strong.
The bigger joints require matching yokes at each end.
I think the u-bolts might be marginally stronger.
If you upsize, install the new yokes first, then measure and order the new shaft. Make sure the springs you plan to run are also on the car.
 
Guys thank you. I will be running MP springs. I think I will end up going to a 1350 series so I will have piece of mind. Am I okay to assume my 489 case pinion is a 10spline unit? Thank you
 
Here's a paragraph from the (Chrysler 8-3/4" Rear Axle Guide) that I found informative on this subject. It could very well be 29 spline.

There are four different yokes that have been used with the 8-3/4″ axle for the ‘7260’ and ‘7290’ style universal joints. The ‘741’/’742′ assemblies used a coarse spline (10 splines) drive pinion. Most of the aftermarket gears also use this coarse spline yoke mount. There is a small yoke for the ‘7260’ and a larger one for the ‘7290’. The ‘489’ assembly used a fine spline (29 splines) yoke. Note: during the phase-in period of 69-71 for the ‘489’ unit, there were several permutations of pinion size and yoke availability. 69-70 ‘489’ units may be equipped with a coarse (10) spline pinion, particularly for the ‘7290’. There are two yokes for the ‘7260’ and ‘7290’ universal joints with fine (29) splines. Two additional yokes were used for the ‘1330’ style universal joint in constant velocity applications, one for 10 splines and one for 29 splines.


Author: Gary Lewallen (aka. Vaanth)
www.bionicdodge.com/Download/Mopar_8_3_4_Rear_End_Guide.PDF
 
I've been using the 7260 joints for years on my race only Dart. I've been 11-teens @ 117 with a best 1.46 60'.....BUT.....I use solid Spicer u-joints, custom driveshaft, a steel billet yoke with u-bolts and an auto trans (footbraking). I tend to be over-cautious & would keep a very close eye on the 8 3/4" with a 4 speed if you hammer on it.
 
Clay/Myron as well as others I respect and appreciate your opinions.
Myron would a solid U-joint be practical for street application with a 4spd? I will put less than 1k miles give or take on this car a year. But it will see some hard launches as we all know a 440/4spd Barracuda will be driven and not towed, LOL. And it will see some hard launches at a local dragway.

Clay you read my mind in telling me that not all are splined the same and that before any yoke is ordered I need to remove the current yoke and count/mic it so I am getting the correct replacement.

My heart is telling me to go with a 1350. Kind of one of those one and done situations. Being I am swapping from a SB to a BB in this car I figure the current drive shaft will need shortening. So why not upgrade. I may talk to someone at Randy's ring and see what they can do for me. Thank you all again:)
 
here is a picture of a 7260/7290 u joint with a grease fitting....looks intact...but the driveshaft is not...u joint was hit with a transbrake for years..
 

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As I usually lean on the side of caution, a 1350 wouldn't be bad idea, especially with a 4-speed. But my solid Spicer 7260 joints have lasted several years with wheels-up launches and the car weighing around 3,540 and has been as heavy as 3,720 for the next slower class. I've never added grease to it. I went with a steel billet rear end yoke because over time, the ears can spread and the u-joint will hammer out. Driveshaft is custom made from better material. Basically, given enough time and "hammering", the weak link in the drivetrain "chain" will show itself.

People have gotten by with less without issues. But the extra insurance can reduce worries. I'd actually like to switch to a Dana 60 if I can ever afford it. It lasted for many years of racing twice a week in a lighter 10 second Challenger I had. But I had lots 8 3/4" parts for my current car and swapping gears (center sections) is so easy. The ring & pinion is now my "weak link" and I check it periodically.
 
Moparman, as Clay's article pointed out the 489 case can have either a coarse spline yoke (early units) or a fine spline yoke (later units). There's an easy way to tell without taking it apart. See what size socket fits the yoke retaining nut. If it takes a 1-1/16" socket it's a coarse spline, if it takes a 1-3/16 or 1-1/4 socket it's a fine spline unit
 
Fishy that is a neat little trick. I will get the old socket set out tomorrow. Thank you
 
I,ve seen a guy at Norwalk a few years ago running 10.0 flat with small u joint.
The car was broken in the pits when I looked at it.
It had broken the 30 spline strange axles and the u joint was still fine lol.
My car has run 11.20 with a 1.50 sixty foot with small u joint.

Duane
 
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