skeletonizer

I am in the early stages of doing a 249 to 231 swap. I have to swap the longer 249 input to the 231. I noticed some play in the planetary gear set. Not having any experience with these things I was wondering if this was normal? 145,000 miles on the 249.

Here is a video of it.

http://s210.photobucket.com/albums/b...620_181538.mp4

OverlandZJ

I cant see your vid, problem is on my end... however there is some play in the planetary assembly, it's normal.

You taking a bunch of pics along the way? We could use a write up on this here. What year and vehicle is the 231 from?

skeletonizer

Allright, got the input swapped and the case installed. The rear drive shaft is now too long. The 231 case is from a 97 xj and has the rubber boot style rear output (no cone) and appears to be a bit longer than the 249.

How does one go about getting the measurement for the drive shaft modification? Or do one of you gurus know off the top of your head?

OverlandZJ

Did you account for the input gear cut change which occured in 95? Mixing the years which you did you have to make sure you swap correctly.

I "think" you can swap the 249's input, planetary and outer sun gear into the 231. It all has to mesh together.

skeletonizer

They (the planetary set) looked identical other than the length of the input. It all went right together and shifts correctly. I will let you know if it turns into a grenade. Would I have been able to shift it through the settings easily and have it freely turn the outputs by hand if it were a different cut?

OverlandZJ

You "may" have gotten lucky, the gear cut occured sometime mid 94 iirc. The gears do look the same with one small exception.. the heel of the gear itself.

If you mixed the gearcuts you should probably notice a whining sound that gradually gets worse.

5-90

How much is "some" - while some endplay in planetary shafts (and planetary gearsets in general - it's called "lash" between gears) is normal, you can have too little or too much.

It can usually be checked either with gage wires (which most people don't have) or with a dial indicator (which is far more common.) Typical spec is something like .002"-.005" of freedom.

Some space is necessary between moving parts, or they won't move. Also, with gearsets, a slight "lubrication clearance" is also necessary, this leaves room enough for oil or grease to be carried on the gear teeth to reduce friction, wear, and heat (and to conduct heat away from the gear contact surfaces.)

Since planetary gearsets have more teeth in contact than typical spur or hypoid gears - or even helical gears - there's usually a bit more allowable lash in the gearset to allow for manufacturing tolerances and suchlike. Make sense?

Nota Bene - be sure the same helix angle is present on the gearsets you're swapping between. Sometime ca. 1994, NP/NVG changed the helix angle slightly (I'm not sure why) on the input planetary set - throwing an early input and late planetary (or late input and early planetary) together will result in draining your gear teeth at the next regular fluid change!

skeletonizer

My bad, the case is for my son's '95 ZJ. Built after the change.

We got it back together and he has wheeled it a couple of times and is gone camping off the edge this weekend with it.

Thanks to all those who responded.