slo90si

Hey i'm having some problems installing an obx lsd into my m2a4. When I put the case halves together with the snap ring in everything is fine until I torque the case bolts. As soon as I torque the bolts the mainshaft is real tight. But if i back the bolts off at all it spins perfect and everything seems fine. Does anybody have any ideas? Any help is appreciated.

extralargenog

iTrader: (1)

Did you reshim the diff???
Check for preload???
New bearings and all that ****??

I just put one in my M2Y4 case, but the only case thats really different that wont work is the M2B4 (JDM OEM LSD tranny). The A4 case should work fine.

That being said/asked.... I HAD TO RESHIM MY DIFF... I had to use more shim, you MAY have the opposite going on (which would cause the binding), or its install error....


Either way make sure to use new bearings,
Measure preload and shim the diff
Check for shaft endplay and shim bearings accordingly, and it SHOULD all work. Ive gone through COUNTLESS H22 trannys and rebuilt even more vbefore finally building a crazy *** straightcut box with LSD and JUST got through doing all of this, but it turned out butter smooth...


Its more involved than simply pounding new bearings on the diff , putting the ring gear ion it and slapping it together...

Good luck, LMK if I can help, I went through REDICULOUS amounts of **** with my car anhailating trannys under power previously...


Ill do what I can to help you out.

slo90si

I installed new oem bearings and races and this is with the stock shims. The preload tightens up just when the bolts are torqued. I tried assembling it without the shim before with the same results but ill try again. How do I check shaft endplay? Dial indicator on the end of the mainshaft and move it back and forth or what? Ive posted before trying to get an answer to this just never got an answer.

extralargenog

iTrader: (1)

Dude that thing looks like something isnt right with it by the pic of the case joint..

Yes to check endplay you would use a dial indicator and what i did was make a steel plate with a hole in it that mouonts to the trans case to mount the dial base to.

It is definately a shimming issue... I dont see how anything else could keep the case up like that... Put the oem diff back in it and see if it works out.. If so, theshims are probably incorrect... Did you have to shim it tighter or loser for the OBX unit???

slo90si

I think your right about shimming it. Here is a pic of the case halves together WITHOUT the gearset but with the diff and shim.

And here it is without the shim


So the shim is 2.23 mm. How do I decide how much smaller to go on the shim?

extralargenog

iTrader: (1)

The gearset itself shouldnt change anything... whats the oreload you have onb the diff??? Can you spin it with the case tqed together???

Seems as though something is going on with how youre putting the shafts in.... IF the diff is shimmed correctly.

Wish I could be there to check it myself..

hahaha

slo90si

I just did it without the gear set to make it easier. Im pretty sure I just need a smaller shim. It spins perfect until I try to torque the bolts to close that gap. So whats the procedure to decide what size shim?

Evs-One

Diff bearing preload should not effect mainshaft whatsoever.

OBX diffs tend to run rather tall, usually going to the thinnest shim, or no shim at all- depends on the unit.

Remove the shim and an axle seal. Install the diff, install trans case, and tighten the case bolts. Tap on the diff from the top side to fully seat it. Take your feeler gauge and measure the distance from the diff housing and the bearing. That will tell you what shim you need.

Install the mainshaft into the case by itself with the upper cover and see if it's still binding. Make sure all shafts are in neutral as well.

Evs-One

Your mainshaft locator(below mainshaft end case bearing, with the tab on it), is completely in the wrong position!! It should be in line with the slot in the gear case cover, flipped almost 180* around! This will keep the case from closing.

Also, clean your mating surfaces! They look gross

slo90si

The mating surfaces has been cleaned as you can see in the pic I have of the diff in the clutch housing side. That mainshaft locator/brake is in the right position it wont even rotate 180 degrees on there. I marked its position relative to one of the shift forks to make it easier. So remove the axle seal and shim and measure between the diff housing and the race or what? Can i just measure the travel of the diff in the case with a dial indicator and decide a shim thickness that way?

Evs-One

yeah, use a feeler gauge. You're not going to get an accurate reading with a dial indicator.

I never clicked on the pics ...didn't knew they were expandable