Rear diff 3bolt VS 4bolt ?

[Stez]

I searched the forum but didnt really found answer to my question, which is:
Why 3bolt rear diff weaker than 4bolt???

except the diameter of axels and the cups mounts i didnt noticed anything what could make 4bolt stronger.

Actually its very interesting which exactly part of all rear assembly tends to broke in drag? any experience would be very interesting...

 

[GRAVEDIGGER]

The 3-bolt halfshaft will break right where the splines go into the rear end because the diameter of the shaft is smaller then that of a 4-bolt. The extra thickness seems to make the difference in the 4-bolt.

 

[Stez]

the diameter of axel is only few mm bigger, not sure if it'll mean something at all.... and ever brake? any experience???

 

[Dave532]

I rallied on a 3-bolt for a few years and never had any problems but that was primariily gravel, ie. less axle torque but higher drive shaft RPM.

I am currently road racing on a 3 bolt with no problems but we do not perform standing starts.

IMO, (never drag racing a DSM) I would stick with the 3 bolt due to cheaper parts, easier access to parts and a wee bit less weight...unless you drag...then I would run a 4 bolt.

Having said all this I still have a complete 4 bolt rear section in the corner of the shop just in case

 

[FonZ454]

While 4 bolt axles are thicker, I think most of the failures on 3 bolts are the axle cups.

Pics make it clear to how the 4bolt cups are superior (from VFAQ)

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[4Motion4g63]

I have broke RIGHT in the Pumpkin in the middle of the splines..... Its a bad break....

 

[pj91gsx]

I have heard of 3 bolt rear ends breaking with 16gs, but I dont have experience. Im sure to break mine when I get my car running.

 

[dsm_Crazed]

I ran a 3-bolt axle on my 91 for the past 4 years, and just put a 4 bolt in it but haven't ran it yet. I've run the thing into the ground with the 3 bolt, going to the track all the time, running 12's and dumping a ACT 2600 clutch with some decently sticky tires and never had an issue with breaking axles. I may just be lucky, but my roommate has ran the same times as me (12.5 and faster) with the same tires that come stock on the SRT-4s (can't remember the name of them) and a 2900 ACT pressure plate and 6 puck ACT disc, and hasn't broke an axle either.

Just my .02

 

[JayRolla]

While 4 bolt axles are thicker, I think most of the failures on 3 bolts are the axle cups.

Pics make it clear to how the 4bolt cups are superior (from VFAQ)

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No it usally fails where the shaft goesi into the center diff. Ive broken two 3 bolts and my brother has broken one. This was on 16g cars with 2600 act clutches. Normal launch around 5500rpm. Here are some pics of where 90% of all 3 bolt failures happen.

http://www.dsmtuners.com/forums/han...-happens-when-you-launch-3-bolt-too-hard.html