How strong are 1310 U Joints?
 

My 69 Bird has 3.08 gears and 1310 U-joints with zerk grease fittings and stock drive shaft. I’d like to go to track using 26x8.5x15 drag radials. The car has frame connectors that are welded in the front and bolted in rear. The engine made 521/631 on engine dyno with headers and 950 HP. In chassis it has Sniper EFI and Long Branch manifolds through 2.5” exhaust. TH400 with 13” Continental converter.

Is this a disaster waiting to happen and I should wait to upgrade drive shaft and 1350 U-joints? Would a good compromise be upgrading to 1330 U-joints.
FWIW, I wouldn’t plan to do this every weekend but maybe a few times a year.

Lots of power, highway gears, slicks. Upgrade the driveshaft.

If you're going to upgrade, don't waste time, money, effort, or enthusiasm with 1330s. Go straight to 1350s.

Do I need the 1350s on both ends or just trans yoke?

Just put Lakewood u joints in it it should be fine.

Are you leaving off the trans brake or the foot brake?

You're having a new driveshaft made. Put them on both ends.

Don't forget to buy the new yoke for the differential.

Foot brake

Uncharted territory for me - when replacing yoke on differential, is it simply remove and replace or are there concerns with crush sleeve or other settings?

The problem with just replacing u joints is you still have old cast diff and transmission inputs. I snapped my transmission input..the u joints held up..also cracked the transmission case.
I was at about the same power as the OP with the same rearend ratio..guess where all the stress goes to???

Go 1350 and be done with it……do the yoke and rear flange …… last thing ya want is the driveshaft ripping the floor up.

Thank you - will research and upgrade

Thanks Chris.

Gotta research rear flange replacement to avoid upsetting preload on pinion.

best thing to do 1350, done, and one less thing to worry about down the line
wish that was the option i was able to do when i needed mine made

a NEW yoke on the diff = new crush sleeve and turning torque measurement.
Open rearend...clean...run a pattern take a pic. (for reference later) remove the differential use a needle type torque wrench to rotate the pinion gear around NOTE: reading. Then remove old flange and crush sleeve. INSTALL new sleeve and yoke. Keep tightening until you have the same rotational torque reading you did before. reassemble rear end, quick check on the pattern to make sure its NOT screwed up....drive on

1350's problem solved

on to the next weakest link...lol

Install a ds loop, I've seen it happen!

Thanks - wasn't intending to get that far into this at this point. Project will have to wait...

If you take the brake drums off you can get a decent measurement of currant rotating torque if you have the proper torque wrench to do so. Than just reset with new yoke and new nut etc...

Usually if your just doing pinion only used bearings are 6 to 15 in lbs, new bearings are 15-30 in lbs, plus about 10 added for the carrier preload.

I have a solid 1310 in my 67 with an 8.5 out of a Nova. Its honestly the one thing that hasnt been upgraded. Unless you consider the solid joint an upgrade.

I have solid 1350 in the front. Its just a PITA to change the differential yoke. Thats the only reason I havent upgraded it yet.

From what I understand the solid joint is a pretty big upgrade from the hollow joint. So if you wanted an in between, you could go to a solid joint.

If you just want to go to a simple track outing before things close out there, and have a little fun with the car, I'd run what ya got.
Being an automatic and a footbrake car you'll likely be just fine for a fun track day, I just wouldn't make a habit of it. Chances are the track won't have "radial" prep anyway, and if the suspension doesn't have some tricks you probably won't be cutting stellar 60 foot times anyway. Go have some fun. If you're already down for winter, then make the upgrade.

I've gone 11's in a pretty heavy car with 1310 joints and stock yokes, again in an automatic car and foot braking it. Never broke the shaft or anything related to it but I wasn't there every weekend pounding on the car either.
Funny, most of the stuff we've raced for years had stock driveshafts in them and never broke a driveshaft. Dad's GTO was running mid 11's since around 2000 with it's original 50 year old driveshaft and some greaseable u-joints in it, lol. Nice wheelies and 1.5 short times. Never broke. He has only recently went to a 1350 shaft good for 1000hp when he upgraded the engine. I did the same on my Chevelle when I swapped to a 4L80E, figured it was a good time to do it.

At some point you'll want to upgrade though. If for nothing else just piece of mind.

1350's with a stronger shaft make the most sense if you're going to spend the money and spend a lot of track time with the car. Upgraded yokes at the same time are part of that, and you'll never have to worry about it again.

Your question on 1330's, our local driveline shop builds a nice heavier steel shaft with 1330's and he gives it about a 600hp/tq rating. I run one of those in one of our street cars with a 5 speed in front of it. This particular car isn't at that power level, and even with the added stress of popping the clutch and horsing around with the car, I don't even worry about it.

Thank you. All I'm looking for are a few timeslips to see what it can do, definitely not a regular journey. Our season goes till about Nov 30th...

Really you can use street tires, not worry about your u joints and just look at the MPH on the top end.

I have slips with the drag radials and with hard tires. The times are dramatically different but the MPH is about the same. That really tells you the power you are making anyway.

ds
 

For sure use a driveshaft loop. Cheap insurance. Ask me how I know.:D

Funny story - just called a local driveline shop to discuss options. Owner says, "That isn't a lot of horsepower - 1310s won't break." He offered to make a thicker walled 3" driveshaft with "high quality" 1310s...