BC847

I run a NON lock-up A518 (46RH) in my '93 W250. During recent repairs, I've found the overdrive planet gears present with substantial galling of the crown and face of the teeth, along with some pitting close to the roots of others (Sun/Annulus-gears as well). There's manually detectable slop in the pinion shafts.
This episode of repairs was brought on by a popped intermediate shaft. It broke clean in the root of one side of the groove where the spacer ring goes behind the transmission's rear planet. Those splines of the intermediate shaft just before engaging the OD planet carrier were twisted. I figure the slop in the OD planet assembly allowed things to bind just enough to . . . .

Time to replace the assembly (typical 240,000 mile wear).

The stock/OEM overdrive planetary in my heap is a 5-pinion (straight-cut teeth) with a steel carrier. It appears exact replacements are being made of unobtainium and are in short supply.

I'm being told that while the later planets running angle-cut teeth are quieter than those with straight-cut teeth, the angled teeth, may not be as strong. At least, the straight-cut teeth are more desirable strength-wise.


-> With perhaps an absolute maximum power of 500hp / 900ft/lbs to the ground, am I risking a weak link there by going to the angle-cut unit? While my mess is no "Big-Dawg", I do launch it hard with perhaps 20psig of boost just before the light goes green (a 60' of 1.8 average @ 6400lbs).

Assuming the straight-cut unit is NLA, it appears my first options might be the standard off-the-shelf retro-fit kits for the 47/48s. It looks like 5 & 6-pinion upgrade kits are available.

I have no experience as to what folks are doing with the 47s & 48s to beef the OD section, if anything, so please pardon my ignorance.

I see that 15 & 22 degree teeth are available. Is there a preference of one over the other?

Thanks folks.

JD730

Dave,

When I was rebuilding my trans I was told by Dave Georend to not even think about using the 22 or 23 degree gears. 15 degree or straight cut is what he recommended. He did make it clear that the sun gear should be inspected closely for pitting on the load side of the teeth and replaced if necessary.

I'm running the OD parts out of a 47RE in my pile of rust.

BC847

Thanks for replying Mike.

Yeah, I figured the 15* would be stronger as it's obviously more like the straight-cut teeth with a larger footprint in tooth engagement terms (the voices in my head say so anyway).

And yes, the Sun-gear teeth are whacked. At this point I'm looking at one of the retro-fit kits that provide all planetary related stuff (Annulus/Planet/Sun).

-> Would you know if there's any difference in the clutch-disc splines (Those that engage the OD annulus outer diameter)?

Thanks again.

JD730

Can't remember, but I don't think there was a difference.

BC847

Thanks Mike.