need GURUS help! 2002 WRX, JDM 4.11 trans, after accellerating, somewhat violent vibrations?

[xbeerd]

ok, so that being said, if it is a 1.1:1 transfer gear,  with a 4.11FD in the front and rear,  if he were to do that test again and spin the front wheel 10 times, it would rotate the rear wheel 11?  or would it be more like 9, regardless, it wont be 10.    then we'd need to find a 3.7 rear dif, which comes from a 06-07 WRX from what i found searching,

 

know of any other years that had 3.7 rear dif?  (other than old school soobs! haha, thats the only thing i knew of a 3.7 until starting this stuff)

[xbeerd]

here is a video of him jacking up the car, spinning the front wheel 10 times.  based on what we said earlier, the rear wheel should turn one less rotation (or close to it) than the front wheel it is 1.1:1 or also turn 10 rotations if 1:1.  well.  the wheel turned 4 times?  

 

 

anyone?

[xbeerd]

Can the USDMcenter dif be swapped in place of a JDM center dif if thats the problem?  we have a center dif from the old trans.

[johnceggleston]

the diff ratios do not match, duh.

 

i don't have any idea what combination of FD ratios would create a ~40% difference.

so i would guess that the mis-match has ''worn'' the center VC so it isn't quite right.

 

i would re-do the test but i would warm up the center diff befor i jacked up the second wheel by rotating the first one a bit. until you can't any more.

or maybe just jack up one wheel and see if you can rotate one wheel at all. the VC should keep it from turning but i suspect you will be able to. at least some.

 

what i'm getting at is , i think the VC is slipping and the rotation test is not 100% accurate.

 

i don't really know the interworkings of the manual trans, but in the auto trans the transfer gear ratio, what ever it is , applies to both the front and rear wheels. so it is a non-issue. (the input shaft is along the top of the trans, all gear shifting is done along that shaft. at the rear of the trans the power / rotations are ''transferred'' to the lower shaft which then sends it forward to the front diff and rearward to the rear diff. but this is how the AT does it. idk about the MT.)

 

still, there is not a FD ratio combination that would creat a 40% difference.

so you still do not know what the ratios are.

 

time to pull the plug, drain the front diff and use a flash light and marking pen to count the teeth on the ring gear.

there are only a few different combinations possible.

can we assume the rear diff is factory?

Edited April 25, 2013 by johnceggleston

[johnceggleston]

 

there are only a few different combinations possible.

ring gear...........ratios

37 teeth = 3.7 (10 tooth pinion) or 4.11 (9 tooth pinion)

39 teeth = 3.9 (10 tooth pinion) or 3.54 (11 tooth pinion) 3.54 is rare, i have never seen it used in a legacy.

40 teeth = 4.44 (9 tooth pinion)

 

the ones in red are the most common for 5 speed manual AWD trans 90 - 04.

but that does not rule out the others for this unusual JDM trans.

Edited April 25, 2013 by johnceggleston

[xbeerd]

from another thread on this, people are saying that due to the viscous center dif, its probably bad.

 

you are correct tho, no rear dif combo will make a 40% difference. something is not right there, the 4.11 rear dif is standard usdm.

 

he said he redid the test with both fronts up.  and got like 9-10 rotations, has to rewatch to verify 9 or 10, as that makes a huge difference here.

 

from the diagram i was lookin at here (attached)

 

 

it shows that the transfer gear is driven off of the center dif.  so.  the ratio to me is something of value.    he is going to pull off the transfer extension and count teeth.  

 

its just kinda hard because he isnt super experienced taking his car apart to this extent. and i don't know that much of how the drivetrains work, having never taken one apart myself let alone the time when im not at work to help him out.  i'd love to work on it so i could learn something, but just need more hours in the damn day!

Edited April 25, 2013 by xbeerd

[johnceggleston]

tell him not to . IF that is part of the issue it is not the total issue.

better to nail down some other stuff first.

 

like what is the front ratio?

 

and there is no reason the replace the VC if the ratios are wrong and the trans has to be replaced.

Edited April 25, 2013 by johnceggleston

[Gloyale]

Pull the drain plug on the trans.  Mark a tooth on the ring gear, then start counting.

 

Grossgary gave you the info.  If you find that you have matching ratios in front and rear, then, it might be worth pulling the center diff section and counting the transfer teeth to see if the ratio is 1:1 or other.

 

 

 

Sidenote to Gary.....small point about 4eat transfer gears.  Rear output is direct from topshaft.....only the front is driven from the transfers and lower shaft.  Although I believe they were all 1:1, it would be possible for it to be other, and have different ratios front/rear.