R6n350GT

Ok new thread to make this specific question easier for others to answer and learn from.

What really is the weak points in the unis, straps, bolts and HS ?
At what HP on tyres like Pilot Sport 4 need to be changed from OEM

Are straps and bolts more important than uni CAP size if the uni HD be it 1330 or 1350 size.

At what HP does greasable unis become and issue


I have 1330 HS but 1350 Diff Stubs.
means spindle end has 1/4" bolts and 1330 unis, while the diff end has 1330 to 1350 uni and 5/16" bolts.

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Here is what i dont know, after the Aluminium Cap in the diff what is the next weak part, Uni or the strap ?

Is a HD 51330X Uni stronger than a conversion 5648X (has thick body but grease nipple).. And really how much difference is there between the 2 at 400 HP or less.

What can the OEM 5/16 strap and bolt with 1350 HD 51350X unis can hand HP wise. Has anyone ever seen a 5/16 strap or bolt fail ?

What is the better option from best to worse for handling 350-400HP and which option is asking for failure with 235/245 Power Sport 4 tyres with a LS1+4l60e


1. 1330 Spindle Yolk with my 1330 Half shafts using HD Dana 51330X with HD Strap Kit from Vansteel that use massive thick straps, larger 8mm bolts. $17e for Unis and $180 for full HD strap kit
* I will still end up having conversion uni on the diff end.

2. 1350 Spindle Yolk with 1350 Half shafts using HD Dana 51350X with OEM 5/16" Strap kit and bolts $99e for manual yokes, $250 for pair of HS with HD unis. $13e for oem 5/16" straps kit.
* Weak point if anything is the oem strap.. if they ever fail idk..

3. 1350 Spindle Yolk with 1330 Half shafts using conversion 5648X 1350-1330 unis with OEM 5/16" Strap kit and bolts. $99e yokes, $34e for conversion unis, $13e for strap kit.
* this is costly option just to upgrade the uni end connecting to the spindle flange to a 1350 so a 5/16" strap can be used..

4. 1350 Spindle Yolk with 1330 Half shafts using conversion 5648X 1350-1330 unis with HD Strap Kit from Vansteel. $99e yoke, $34e uni, $180 for HD Vansteel strap kit
* the possible weak strap is now eliminated but now the greasable conversion uni is the weak point if thats even a thing...


The best scenario is manual flange, HD strap kit, 1350 HS, 51350X Uni but that is $630 USD...


Ahhh... Please someone help. What is the area i actually need to focus on.

HeadsU.P.

The "Ears" on the end of the driveshaft. I have seen those removed from brute H.P. and gummy M&Hs.

R6n350GT

So thats another weak point , but are the 1350 HS ears any stronger? They may have a wider Diameter but no thicker ?

I have some some pics of unis torn in half meanwhite the oem strip is still sitting there... Someone else wrote their 1/4" bolt sheared off and destroyed rear end also...

I wonder if 5/16" oem straps and bolts ever fail.

Then i could just have conversion unis all round so i can use 5/16" straps but then the grease fitting is a weak point if thats even a weak point 350-400hp wise with street tyres....

Id rather spend money on hydroboost than replacing parts that are fine.. Hope some others with experience can chime in

HeadsU.P.

I can tell you to that the Spicer solids are the way to go. And that automatics are more forgiving on the drivetrain than clutch dumpers.

As far as the pinion straps, when you think about it, they really don't take the full brunt of the torque. They merely hold the U caps in place thanks to that little tab thats on the yoke.

Someone wrote years ago on this forum that a stock rear will handle over 350 RWHP.
H-m-m-m-m, pretty broad statement not knowing how sticky the donuts are.

R6n350GT

I emailed Spicer about their 1350-1330 U joint with grease fitting. Ill post a pic later as it is quite a large body unit.. But i need to know what point that fails at...

If they said not good past 350-400HP then i will have to get new manual yokes, new DS and 1350s.

Then i must decide are new oem 5/16" straps and bolts good enough now that i have Solid HD 1350s.... Your saying they would be ?

HeadsU.P.

I will make this disclaimer and say you will be fine. But like I said, its really up to what tires you are running. The tires are not the weak point but rather the strong point if you know what I mean.
Two cars side by side. One has over 800 RWHP but with skinny little VW tires.
The other car has 150 RWHP but has 12" wide sticky slicks.
Guess which U joint will break?

71VetteLover

The one made in Hong Cong.

R6n350GT

Well either 245 or 235 Michelin Power Spot 4 tyres on 17s

ill wait and see if Dana Spicer reply.

I did read that conversion unis handle less power than a joint of the same series at even the smaller series side (ie a solid 1330 is stronger) - from some shop opinions on a forum

also a solid 5-1310x it is only 100ft lbs off the 1350 greaseable uni
Im not sure what that means in HP terms..

bence13_33

I agree with that to a certain extent. Yes they do hold the caps in place, however a more suitable cap vs. a strap I would think would help take some of the burden from the torque as well as be structurally more solid. The caps also generally have another set of "ears" machined into them which also helps (the straps obviously do not). I don't think caps are a bad idea, and do increase strength....straps do have a tendency to flex/stretch.

R6n350GT

from everything i have read i only saw unis torn in half, 1/4" bolt shear off. Not seen and actual straps brake. Has anyone ?

Maine just higher strength allen key bolts will bee good enough ?