car_nut15

iTrader: (8)

Hey guys,

So about 2 months ago I got my car tuned. The following week I took it to the track for the first time on the new setup and on the third pass broke the rear driver axle shaft. Put a new one in and took the car to the Buschur shootout 2 weeks later. On my 5th pass I broke another axle shaft (Passenger rear this time) The Boostin performance guys just so happened to be watching that pass and in the pits told me my car needs solid diff bushings. I currently have energy suspension poly rear diff bushings. Could this be my issue or is it time for upgraded shafts? The car makes about 740hp/530Tq

I am using M/H drag radials at around 15psi. What's interesting is how the shafts are breaking. Both shafts broke at the splines in the diff. What's also interesting is that the first time I broke a shaft the CV boot on the other side had popped off as well. It looks as though the diff is moving and the clamps on the boots are actually hitting the body. I'm thinking when the diff moves it puts the shafts at an awkward angle and therefore causing them to break where they do. I have a set of solid diff bushings on order but If anyone has any other ideas/suggestions that would be greatly appreciated!

Pic of the broken axle can be seen here on the first page:

https://www.evolutionm.net/forums/ev...-mani-e85.html

mkcolgan

iTrader: (3)

I'd think if you kept breaking the OEM shafts it might be time for some upgraded ones...

This group seems to think 500 is the limit. VVVV

https://www.evolutionm.net/forums/ev...xles-hold.html

meckert

iTrader: (11)

Depending on the outcome-- you could have your shafts cryo'd and shot peened and that should take care of the axles strength issue--if indeed its not caused from binding as suggested. Good luck.

Boostin Perform

iTrader: (7)

We recommend upgraded axles if you keep breaking them. However we're been successful using OEM axles along with the Torque Solution Mustache Bar Eliminator w/ Solid Bushings. Let me know if you have any other questions.

car_nut15

iTrader: (8)

I think this is the route I'm going to try before spending the big $$ on shafts.

Boostin Perform

iTrader: (7)

Keep me posted, I can have one shipped out right away!

Boltz.

iTrader: (42)

You can take my advice with a grain of salt, but if it were me, I'd be looking at tires/suspension/chassis before bigger shafts.

Based on what you are saying I'm guessing you're wheel hopping causing the diff to move so much and thus the axles to break. If you distribute the power linearly, the diff shouldn't be moving as much as you are seeing. Its the frequency of losing and gaining traction rapidly that is likely causing the diff to move as much as it is.

If my thinking is right, by replacing the axles you would then change the weak point in your drivetrain to a different part, trans, transfercase, diff, who knows.

Do you have any friends that have softer sidewall tires that would let you test them (something like a QTP)? It could be the radials you are running...

car_nut15

iTrader: (8)

I am getting absolutely no wheel hop. Back in the day on street tires I would get slight wheel hop which is when I purchased all drivetrain bushings. I thought the m/h radials were considered pretty soft? Pretty sure there is quite a few people running these tires successfully that aren't breaking drivetrain parts.