THICK GEARS?

StokesCo94HB

New Member
Joined
Jul 24, 2006
Location
Stokes County, NC
What’s the deal with thick gears? I know that you can use them on the 3.92 and down carriers, but I've never heard much about people using them. Are they weaker or something or am I just misinformed. The reason I’m asking is b/c I’m about to buy my gears (4.88’s) for my D44 and I don’t want to by a new carrier.
 
maybe this will help ya. I put this chart together awhile back. Its got information / specs on a few axles (common to jeep / project build ups)
Axle Identification Chart
Their are some missing specs on a few, if anyone knows these, let me know and I'll add it for future reference for everyone.
(just tryin' to help out)
 
Numerically lower gears have a higher number of teeth on the pinion, which requires a larger diameter to achieve. This is why there are typically two different carriers for the same axle. Since numerically higher gears have smaller pinion heads, the ring gear has to be closer to the centerline of the pinion. There are generally 3 ways to accomplish this: buy a the proper carrier, run a thick style gear, or run a ring gear spacer with a standard gear.

The standard gear puts the torque on the carrier closer to the gear mounting flange. The thicker gear effectively has higher leverage because it is farther to the mounting surface. It's like using a ratchet with no extension versus one with a foot long extension. With the longer extension on the ratchet, you must support the head of the ratchet, or it will put some strange twists on the bolt/nut and possibly round it off. In the end, the net effect is slightly more stress on the ring gear bolts, but the amount is relatively small compared to the amount of stress than can withstand.

A ring gear spacer increases the stress on the bolts in the same way as a thick gear, but also adds another potential shear point for the bolts, and another potential area for the gear to slide. The torque between the ring gear and the carrier is distributed between plain shear in the bolts, and friction between the flat surfaces caused by the tightness of the bolts. Since the static coefficient of friction between hardened steel is .78, that means that resistance due to friction is 78% of the compressive force of the bolts is translated and prevents sliding between the surfaces. Once the plates slide, that becomes .42 (42% of the force), putting much more stress on the bolts.

I guess in summation, the best option is a proper carrier, however, a thicker gear works nearly as well. A ring gear spacer will work, but it is extremely crucial that the bolts are and remain properly torqued, and should be avoided if better options are available. I personally would run one, but would be constantly worried about the bolts.
 
thats an awesome post, lots of great info, thanks. What if i bought thick gears for a rubi. They use larger ring gear mounting bolts so id have to drill out the holes on the carrier, you think that would compensate for the added stress of the thick gears?
 
keep in mind that a Rubi's differential is different from a regular D44. Many of a debate has been spun about it not being a true 44. Come to find out, its a different housing design that they used. They do take a thick standard rotation gear set. Just make sure you have the correct torque specs for each component.
 
I don't think larger bolts would really make much difference, as the smaller bolts can handle plenty of stress. I would be more leary of drilling out the carrier, but I don't have any good reasons, other than it won't have as good of a finish and the holes might not be dead on center, neither of which are really crucial.
 
If it is a regular Dana 44 (Not a Rubi 44) - a new carrier is cheap enough that there is no point in playing around with short cuts.
 
Im going with thick gears from a Rubi for my Xj rear. It allows me to use the same carrier but you have to bore out the holes on the carrier to except the wider bolts the ring uses.
 
Back
Top