Rear Diff Weak Link

[01slowbra46]

Hello All,

I was just wondering what everyone thinks the weak link in our diffs is? I have upper control arm/mount, lowers, did steeda sports and koni sports and somehow the car hooks harder than ever. Axle tubes are also welded.

Went to the track the other day expecting to go slower and to my amazement the car dead hooked both runs to where it actually hurt my 60". Car is an mt82 car with MT drag radials as I didnt really want to get a bias ply with radial non skinny fronts. First run I left at around 3500 slipping the clutch. Second run I dumped it at 4k and still dead hooked. I was scared to break it since I was 3 hours from home. Both times I went 11.79@121 with a 1.88 60.

What do you think would shatter first? An axle or one of the spiders? I've done a bit of searching and all i find is people twisting axle tubes. In previous year mustangs ive shattered diffs but they we also high mileage.

Any suggestions as to what I should upgrade to? I drive the car on the street most of the time, with occasional auto x and drag passes.

 

[wolfman311]

Hello All,

I was just wondering what everyone thinks the weak link in our diffs is? I have upper control arm/mount, lowers, did steeda sports and koni sports and somehow the car hooks harder than ever. Axle tubes are also welded.

Went to the track the other day expecting to go slower and to my amazement the car dead hooked both runs to where it actually hurt my 60". Car is an mt82 car with MT drag radials as I didnt really want to get a bias ply with radial non skinny fronts. First run I left at around 3500 slipping the clutch. Second run I dumped it at 4k and still dead hooked. I was scared to break it since I was 3 hours from home. Both times I went 11.79@121 with a 1.88 60.

What do you think would shatter first? An axle or one of the spiders? I've done a bit of searching and all i find is people twisting axle tubes. In previous year mustangs ive shattered diffs but they we also high mileage.

Any suggestions as to what I should upgrade to? I drive the car on the street most of the time, with occasional auto x and drag passes.

Your next weak links will be your axles, clutch, and trans in my opinion.

 

[wolfman311]

Your next weak links will be your axles, clutch, and trans in my opinion.

Also your stock drive shaft is a weak link as well.

 

[5lho]

The weak link could be anything straining the car with drag radials. I dead hooked up to 6K on a slick with an MT 82, over 100 passes and no "weak link" emerged, not even the clutch. The rear end and driveshaft are strong as hell on this car. Anything can be broken but, for stock stuff it's pretty awesome.

 

[01slowbra46]

Also your stock drive shaft is a weak link as well.

Forgot to mention I have a 1 PC as well. Guess theres only one way to find out what will break!

 

[5lho]

Yep...I predict you'll be fine for a good while here.....

 

[Dave_6]

I know the stock axles are 31 spline; so since I'm bolt ons only should I have any worries about dumping the clutch at 5500 or so on slicks? Took it to the track on slicks (26x10.5 stiff wall) for the first time last weekend but I slipped the clutch some every pass trying to not break the diff. Best 60 foot was only a 1.77 so I know it can do a good bit better.

Yes I have a one piece driveshaft (mods in sig).

 

[5lho]

I know the stock axles are 31 spline; so since I'm bolt ons only should I have any worries about dumping the clutch at 5500 or so on slicks? Took it to the track on slicks (26x10.5 stiff wall) for the first time last weekend but I slipped the clutch some every pass trying to not break the diff. Best 60 foot was only a 1.77 so I know it can do a good bit better.

Yes I have a one piece driveshaft (mods in sig).

Dump it and let it eat. I did over 100 clutch dump launches in my 2012, at rpm from 4500-6000, no problems whatsoever. 1.5 60 that way, 11.91 on a tune and tire only.

 

[Turd Fergusen]

The clutch packs in the diff will wear out before you break an axle

 

[MKMotorsport]

C-clip eliminator kit? Seems odd to me to weld up the axle tubes but not address that.

Edit: Maybe not as much an issue with the 31 spline rears in the newer cars vs. the old Fox Body axles....or most go to 9" housing ends it looks like....

 

[Dave_6]

Dump it and let it eat. I did over 100 clutch dump launches in my 2012, at rpm from 4500-6000, no problems whatsoever. 1.5 60 that way, 11.91 on a tune and tire only.

Guess next time I go then I'll just dump it. Probably easier on the clutch too.

 

[01slowbra46]

I know the stock axles are 31 spline; so since I'm bolt ons only should I have any worries about dumping the clutch at 5500 or so on slicks? Took it to the track on slicks (26x10.5 stiff wall) for the first time last weekend but I slipped the clutch some every pass trying to not break the diff. Best 60 foot was only a 1.77 so I know it can do a good bit better.

Yes I have a one piece driveshaft (mods in sig).

Out of curiosity, what are you trapping? We have damn near the same mods.

 

[01slowbra46]

These cars like to spin axle tubes without it.

 

[Dave_6]

Out of curiosity, what are you trapping? We have damn near the same mods.

I only ran 1/8 mile but my mph was only 89 to 90. I know slicks hurt mph but it seemed low to me. Granted I really only have headers/exhaust and a tune for power mods. Last time I ran on my 19s it went 92 to 93.

 

[q6543]

Dead hook will usually lead to a little bog and is less than otimal.

you want a Rotation or 2 but at the same time have the tire recovering while rpm increases.

that's why most people want a bias ply on a stick, radials Don't tend to recover the best.

121mph is solid, what mods' and I can't help but wonder how your time would Look with a 1.5x 60

 

[corysmach1]

I've left at 7200 on a 2 step. Bias ply's helps save the rear end. It will eventually let go. From what I have seen it will be an axle.

 

[Scott8583]

I run an auto, but I'm putting down 850whp on stock axles (1.38 60's but soon to be lower). The spider gears or clutch packs will go first.
I wouldn't swap stock 31's for aftermarket 31's. If your going to swap might as well go 33spline. The disk brakes will keep the axle from coming out if one should happen to break. Also my opinion on the axle tubes twisting is due to the extended leverage of LCA relocation brackets and unwelded tubes.

 

[lindermant]

a diff cover with bearing cap load bolts is something to consider...

https://www.lpwracing.com/Ultra_FORD/Ultra_FORD.html