help, I keep busting my rear end

[btmatt]

I hate my tuner.. after tuning my HCIE LS3, I have broken my diff twice in the last week. Here is what I got:

1. 1967 PT Camaro, 500RWHP NA LS3, Tremec Magnum 6 speed (2.97 1st gear)
2. PEM 9" ford housing, 31 spline axles, detroit locker, 3.89 gears
3. Nitto NT05 rear tire; ~12" wide, 26" tall.

First time out, we broke the case and destroyed 1310 ujoint; Ford grey iron case and pinion support. No biggie, I always figured that would have been the weak link.

We then rebuilt/upgraded the case to Strange Nodular 3.06 case, Daytona Pinion Support, new gears, bearings etc. and proceeded to snap/shatter the drivers side rear axle at the spline transition. This was at the drags, during launch, on street tires.

I know that there are others on here with wayyy nastier combos than mine that are holding together. Let me know what you are using

[pannetron]

You might want to talk with the folks at Mark Williams Engineering, they specialize in bullet proof parts for drag racing.

[btmatt]

Already called them this morning. Might have to wait on that second stimulus check to afford them. Ha


You might want to talk with the folks at Mark Williams Engineering, they specialize in bullet proof parts for drag racing.

[John McIntire]

I wouldn't necessarily blame the tuner.
A stick car that hooks is definitely going to stress some parts as you've already found out.
Sounds like some stronger axles are in your future. Look on the bright side, you're making some power and your suspension must be working!

[btmatt]

Nah, tuner did a wonderful job on the car. We just found the "new weak link"

I tease my son, if it were cheap and easy, we would all be making 1000hp, 1/4 times in the 9s, and run 200mph in the mile.


I wouldn't necessarily blame the tuner.
A stick car that hooks is definitely going to stress some parts as you've already found out.
Sounds like some stronger axles are in your future. Look on the bright side, you're making some power and your suspension must be working!

[Lonnies Performance]

1310 u-joints & yokes are not performance oriented....
I have broken these with 300hp.

A 31 spline axle is only rated to 500hp.
I just had this conversation with Strange last week.

Upgrade to 35 spline axles & a matching center section with a good Driveshaft & 1350 u-joints.
Then it will handle 1000hp.

I ran a 33 spline 12 bolt with 33 spline axles launching at 5K on slicks with 650whp & went 9's.
Yes, this will eventually twist the input shaft off of a T-56, but the rest of the drive line held just fine for years.

[andrewb70]

It is also possible that your housing is not true and it is stressing the rest of the components.

Andrew

[btmatt]

thanks for everyone's input. Looks like we are looking at a 35 or 40 spline uprade.

just need to choose a vendor and move forward. Matt

[Lonnies Performance]

40 is overkill unless you plan to be over 1000rwhp.

Here are some axle Ratings:

30 Spline: 6,200 ft./lbs. (per axle)
31 Spline: 7,000 ft./lbs. (per axle)
33 Spline: 8,200 ft./lbs. (per axle)
35 Spline: 9,600 ft./lbs. (per axle)
40 Spline: 12,000 ft./lbs. (per axle)

Remember it is possible to put nearly all power to 1 axle with a good posi or locker.
Wheel hop is even more destructive.

In your case, say 500ft/lb x 2.97 trans x 3.89 rear = 5777ft/lb potential.
Add a safety factor & take shock loads into account.

Strange rates their 35 spline street axles to 800hp & their race axle to 1000hp, based on drag strip launches with slicks.
40 spline are spool only.

[btmatt]

thanks again for everyone's input. Placing order today for 3.250 case, 35 spline differential, and alloy axles.

[badazz81z28]

You blame a tuner for broken parts? I agree, just hearing you have 1310
U-joints tells me your part combo probably isn’t matched well.

[btmatt]

Really?? If you read the whole post you would know that my tuner comment was a weak attempt at humor. Regarding the combo, we always new the diff was the weak link and finally got to power levels that manifested in some serious breakage. Trust me, the rest of the combo is "serious stout" and we have thoroughly embarrassed many cars considered "out of our league" due to the choices in our "combination".

I posted looking for recommendations from others before I spent a lot of money and made similar mistakes. And, big thanks to all who have helped with that.

So while we are here, why don't you give me your combo if you are going to take shots at mine?



You blame a tuner for broken parts? I agree, just hearing you have 1310
U-joints tells me your part combo probably isn’t matched well.

[badazz81z28]

Really?? If you read the whole post you would know that my tuner comment was a weak attempt at humor. Regarding the combo, we always new the diff was the weak link and finally got to power levels that manifested in some serious breakage. Trust me, the rest of the combo is "serious stout" and we have thoroughly embarrassed many cars considered "out of our league" due to the choices in our "combination".

I posted looking for recommendations from others before I spent a lot of money and made similar mistakes. And, big thanks to all who have helped with that.

So while we are here, why don't you give me your combo if you are going to take shots at mine?


Let see...LS7 engine, modified 560hp to the tires, Wegner Drive, C@R radiator with PSC and EOC, DSE LT headers, 3" dual exhaust, Quick-time Bellhousing, McLeod RST twin clutch, T56 Magnum, custom made 4" aluminum driveshaft with 1350 U-joints and of course 1350 yokes. Going into a full floater ford 9" with Moser 3rd member with isotopic treated gears and full tig welded Gear FX housing. 31 spline axles, 14" BAER brakes on all 4 corners. Detroit Speed frame, subframe connectors and a Quadra link rear suspension, Mini-tubbed, Forgeline wheels with BFG rivals. Where's my weakest link?

[badazz81z28]

Probably your driving skills.

^^^^^^^^^^^^^^^^^ Attempt at humor.

On a serious note, do you just cruise around the forums dumping your condescending attitude on everyone you disagree with?


The driver is probably a very accurate statement. Telling you a 1310 U-joint is a poor mis-match for a performance application is inappropriate? You ask a question...Ill give you an honest opinion. Look at my build...it didn't start that way. I think I'm qualified to give you my opinion on parts...whether you like what I have to say or not. I bet you didn't expect to see what I actually have on my car.

[btmatt]

LOL, and I thought i would be the only one baited into a smartass reply


Probably your driving skills.

^^^^^^^^^^^^^^^^^ Attempt at humor.

On a serious note, do you just cruise around the forums dumping your condescending attitude on everyone you disagree with?

[btmatt]

31 spline axles and 31 spline diff and carrier; otherwise parts list between the 2 are surprisingly similar

183476183478


Let see...LS7 engine, modified 560hp to the tires, Wegner Drive, C@R radiator with PSC and EOC, DSE LT headers, 3" dual exhaust, Quick-time Bellhousing, McLeod RST twin clutch, T56 Magnum, custom made 4" aluminum driveshaft with 1350 U-joints and of course 1350 yokes. Going into a full floater ford 9" with Moser 3rd member with isotopic treated gears and full tig welded Gear FX housing. 31 spline axles, 14" BAER brakes on all 4 corners. Detroit Speed frame, subframe connectors and a Quadra link rear suspension, Mini-tubbed, Forgeline wheels with BFG rivals. Where's my weakest link?