When is the bigger U joint needed?

I’m having a driveshaft made for my big block and I went through a couple 9.25 axles before I found a good one to build. I didn’t realize I had installed a small U pinion yoke until I measured for the driveshaft. I do have a large yoke on the shelf and I guess it wouldn’t be too much trouble to swap it out?

I told my driveshaft guy to just put a combination/conversion U on the shaft for now after he shortens and balances it- I have no plans for stickier than 11” wide summer tires so I figured the U joint would probably be fine.

But it’s nagging in the back of my mind. I’ve pretzeled driveshafts before with a stickshift and slicks and broke a thirty year old universal once but with an automatic trans and street radials?

So should I swap it out and call the driveshaft shop to change my order? Or stop worrying about it?

Thanks fellas!

Call them

I can't see reason to use less than a 7290 joint and if you are spending the money why not a 1350?

You can't hurt yourself with a bigger joint in joint.

I always use 1350 u joints. Never bothered to test different u-joints, I just automatically use the 1350 in every build. It seems to be the industry standard these days.

Yep.
Do it once, do it right

I tried using 7260 and 7290 joints. It was a no-go in my combo. I even destroyed a FRONT yoke after a u-joint broke on the starting line at the dragstrip. 1350 Strange shaft and u-bolt rear yoke solved my issues. I even added 150 HP and zero issues.

I've used a bunch of Neapco H.D. solid 7260 U joints in a lot of my old drag cars with good success
My current drag car came with 1350 on both ends, it had a blown B1 motor in it before I bought it as a roller, both sizes work for the applications
I have broke stock type u joints and yokes at the track also
It is your call on your car and what parts to use

Put a big yoke on it, a friend here has just broke his front U at the track as its starting to hook...its only a mild 440 around 360hp/450TQ, 3700lb roadrunner on Dot drag tyres, 727- stockish verter....he's going Big.

Go big. I started breaking the factory driveline stuff in my cuda running mid 11s at 3700 lbs. Go big once and be done w/ it.

1350's both ends...

D’oh I called him and he said he already put a small U end on my driveshaft instead of the conversion U. No big deal it’s just a shortened old truck driveshaft. I’m going to run a loop anyway so we’ll see how long it lasts. If or when I crack it I will throw the big yoke on my pinion.

Thanks
Rdr

The tranny will need looked at if you break the driveshaft. Keep that in mind

1350s will cover up other problems.
Knock on wood, after all these years, never broke a joint or driveshaft.

Good 1350s, if you can get a 1350 yoke for the rear. Why a 9.25? Given enough horsepower/weight/radials/sticky track, forged slip yokes will break too. A good billet piece will take care of that.

I wanted to do a 9.25 to be different and to be a cheapskate. I did yukon axles, crush sleeve eliminator kit, bearings, seals, and got everything back in spec for small money amd the axle was a parts trade. (Actually went through 2 to find a good one) I’m hoping street tires mixed with a light rear end in a 3000lb pickup truck will make traction always be the weakest link in my driveline. I was actually considering running an 8.25 because I have three of them but they look like a toy next to the 9.25. I did spend a few bucks on bling and bought a cast B&m finned cover which looks really nice under there.

Oh and a 70’s ramcharger 9.25 is already set up for 5 on 4.5” bolt battern and came in a width that fits perfectly in my tubs with my wheels. My ZJ rear disc brake system bolted right up too with just an enlargement of the central pilot hole which is another plus.

So no drag radials, no heavy weight, no track, and just a stock yoke... wish me luck, “hold my beer” haha

I ran the small u-joint and yoke with the stock
little straps and bolts on my racecar
till I blew the ring gear on my stock 8 3/4..
once it blew the ring I changed over to a alum
center 8 3/4 with a 1350 u-joint.. its still
running fine but the car is for sale now