CV Axle/shaft strength

Zep5.0

Zep5.0

6th Gear Poster
Birdcats Supporter
Joined
Sep 22, 2023
Messages
580
Location
Waterloo, Iowa
Vehicle Details
1991 Mercury Cougar LS 5.0
Country flag
Didn't find this here yet. I'm sure it was discussed to death on tstsnbn. What is the max whp for stock CV axles/shafts? And are there any other options for performance other than DSS? I believe Cobra shafts are barely too short.

Are any stock units better than others? I remember hearing about hardened outers on MarkVIII, but not sure it's true. Also heard some SC shafts may have been thicker.

Thanks for any info.
 
From top to bottom, here is a passenger side and a driver side halfshaft from a manual SC, and both are thicker than the ones in naturally aspirated MN12s and the Mark VIII.

P2140139.JPG

I'm not sure how well you can correlate a specific power figure to halfshaft durability. There have been some high-powered MN12s that were just fine running stock halfshafts. Most if not all of the broken halfshaft stories I remember reading about happened with manual cars on drag radials.
 
I have an '89 SC in my garage right now being worked on that puts just over 400WHP down on stock halfshafts. It is a 5 speed car that has run 11's.
 
Ron twisted one off, and iirc, he's between 500 and550 hp.
Mikey found that the cobra shafts fit, by pulling out.
 
The shaft portion of the halfshafts aren’t what usually fail, it’s the 28 spline stubs going into the hub or diff.

Supposedly the reason for the SC fat shaft was NVH related, not strength
 
The shaft pulled out of my inner CV when I pulled them, so I'm deciding how much money to spend. New duralast are $120. I could replace them 10 times before the cost of DSS ..
 
From what I've seen the reason they break is because of wheelhop - itself usually caused by worn out rubber rear end bushings, or bushings too soft for the power level (e.g. rubber < poly < delrin < aluminum).
 
Launches on drag radials puts them on borrowed time IMO, wheel hop or no. Slicks seem to be more IRS friendly since the sidewall gives when you launch, cushioning the harshness a little
 
I've been drifting on SC CVs for the last 3 years. 80mph, then locked stopped, then clutch kicked back to 60ish MPH with a load.

What I have noticed is my axle nuts keep loosening up.
 
Wile E. Coyote said:
I've been drifting on SC CVs for the last 3 years. 80mph, then locked stopped, then clutch kicked back to 60ish MPH with a load.

What I have noticed is my axle nuts keep loosening up.
Click to expand...

Torque a second nut over the first nut
 
Rear nut loosening is a sign of a worn bearing. I've had that happen before. Usually after a hard session with the curvies.
 
Grog6 said:
Rear nut loosening is a sign of a worn bearing. I've had that happen before. Usually after a hard session with the curvies.
Click to expand...

I’m conflicted, I see your point as we discussed before but I will say I’ve done a lot of doughnuts and powerslides(I won’t delude myself in calling them drifts in my case) but 50k killed my right one and it was a Timkin bearing installed correctly and the nut was hand tight when I took it off, so either it just failed very prematurely or my habits caused the nut to back off and that fact let it fail prematurely. For my own piece of mind I hope it’s the latter haha

At the very least a second (factory)nut doesn’t hurt.
 
XR7-4.6 said:
I’m conflicted, I see your point as we discussed before but I will say I’ve done a lot of doughnuts and powerslides(I won’t delude myself in calling them drifts in my case) but 50k killed my right one and it was a Timkin bearing installed correctly and the nut was hand tight when I took it off, so either it just failed very prematurely or my habits caused the nut to back off and that fact let it fail prematurely. For my own piece of mind I hope it’s the latter haha

At the very least a second (factory)nut doesn’t hurt.
Click to expand...
I'll give it a shot. I've thought about tac welding it too.
 
I don't put much faith in Timken stuff lately. The two front hub assemblies I got from them lasted less than a year. They sent a replacement under warranty that lasted a week. The replacement Moog has been fine in the 80k since I trashed the Timkens.
 
theterminator93 said:
I don't put much faith in Timken stuff lately. The two front hub assemblies I got from them lasted less than a year. They sent a replacement under warranty that lasted a week. The replacement Moog has been fine in the 80k since I trashed the Timkens.
Click to expand...

Mine weren’t recent, I hub swapped in either 07 or 08. It was one of my first “real” mods.
 
theterminator93 said:
I don't put much faith in Timken stuff lately. The two front hub assemblies I got from them lasted less than a year. They sent a replacement under warranty that lasted a week. The replacement Moog has been fine in the 80k since I trashed the Timkens.
Click to expand...
I typically stick with Timken or SKF, but I have been moving away from Timken. On the last rear wheel bearing change on the T-Bird I used SKF. A lot of Timken stuff seems to come out of South Korea lately. I believe Moog are made by National which is a good brand. The last wheel bearing I did on a Subaru I ordered BCA and I believe it was hecho en E.A.U. for what it's worth. Seemed like a quality piece. I may try them more in the future.

XR7-4.6 said:
I’m conflicted, I see your point as we discussed before but I will say I’ve done a lot of doughnuts and powerslides(I won’t delude myself in calling them drifts in my case) but 50k killed my right one and it was a Timkin bearing installed correctly and the nut was hand tight when I took it off, so either it just failed very prematurely or my habits caused the nut to back off and that fact let it fail prematurely. For my own piece of mind I hope it’s the latter haha

At the very least a second (factory)nut doesn’t hurt.
Click to expand...
I have to believe the nut is loosening up and causing the bearing to fail and not the other way around. Probably not a bad thing to check every oil change.

@Zep5.0, sorry for crapping up your thread about halfshafts with a bunch of my opinions on wheel bearings and axle nuts.
 
No worries, all important stuff. I had bought the dorman axle nuts a few years back in my parts hoarding. Now I'm thinking I'll reuse my stock set, and see if I can find another to double them up. My spare IRS shafts were mangled so bad we had to burn the nuts off. Basically there were no threads left on the shaft.
 
Zep5.0 said:
My spare IRS shafts were mangled so bad we had to burn the nuts off. Basically there were no threads left on the shaft.
Click to expand...

I have this exact problem on the Mark. For now the bearings seem OK, but with nearly 225k on the clock, I find myself wondering when they'll say "enough is enough!"...
 
Zep5.0 said:
No worries, all important stuff. I had bought the dorman axle nuts a few years back in my parts hoarding. Now I'm thinking I'll reuse my stock set, and see if I can find another to double them up. My spare IRS shafts were mangled so bad we had to burn the nuts off. Basically there were no threads left on the shaft.
Click to expand...
For what it’s worth, I have been reusing the stock axle nuts, both front and rear, for over 20 years now, and I have never had one back off, regardless of the level of hooning. I have heard many stories of the aftermarket ones either cutting up the threads and destroying the axle or the front spindle, as well as them loosening up. The factory ones I simply look at to make sure they aren’t rusted to hell or physically damaged, and if they look fine, then just go full send with the impact.
 
Last edited:
Koyo makes good bearings too, they’re an OEM supplier as well. It doesn’t bother me other than my principled hatred of corporate buyouts/mergers.
 
I agree with you, every electronic company I've worked with in the last 30 years as been bought out by someone. Hell, in 2015, I had two companies designing a high voltage opamp for us; one company made one at 120V, one only hit 100. When I placed an order of the 120V part, the losing co bought the winner! I talked to the sales guys sometimes daily; It sux to know the decision you make will make someone you know well out of a job.
On the cooler side, I used a part once that was going eol, there was no sub, and I talked to the company, and asked; If I order 200k of these a quarter, will you keep making them for 10 years? I kept a factory open for 10 years, and everyone on the line was able to retire. I got a plaque from the union. :)
 
You must log in or register to reply here.

Similar threads

Back
Top