Intermittent shuddering
 

My 1992 JDM SVX had a blown transmission when I bought it, so we swapped a transmission out of a parts car I bought.

I never drove it before the trans was swapped over.

I have found that it will shudder or vibrate at low speed intermittently.

I've taken it to the Subaru dealer and at the moment his best guess is that the trans is not from an SVX and there is possibly the wrong ratios between the trans and the diffs.

Has anyone here experienced what happens when there is a mismatch between trans and diff ratios ?

I have email the owner of the parts car to try to find out it's history. Hopefully one answer is that they swapped the trans & diff in the parts car, so all I have to do is swap the diff over to eliminate the shudder.

Thanks, Shane

Re: Intermittent shuddering
 

If you can get the serial number off the transmission it should be possible to find out what the donor car was and the ratio too.
I know it works here in North America so it shouldn't be any different for Subarus over there.

Re: Intermittent shuddering
 

TZ102YBABA-CF
The dealer tells me this is out of a 1994-96 2 litre Legacy.
Next step is to find out the correct ratio to match this transmission and then pull the cover off the parts car rear diff and count the teeth.

Hopefully the stars are in alignment and we have a match.

Re: Intermittent shuddering
 

Assuming there is a ratio mismatch problem and I can't fix it immediately, as an interim measure could I insert the FWD fuse so as to disable drive to the rear wheels ?

Any comments on running like this for a few weeks until I can sort out replacing the diff ?

Re: Intermittent shuddering
 

I found this somewhere else, describes a technique to work out the ratio of the rear diff without disassembly.

"jack up the rear of the vehicle and turn the rear wheel. count how many times the driveshaft turns for each turn of the wheel. 41 turns of one to 10 turns of the other gives you a 4.11 gear ration. 44 turns of one to 10 turns of the other gives you a 4.44. i would imagine those are your two options 4.44 or 4.11"

Re: Intermittent shuddering
 

there are several ratio's, depending on different things, the usa cars got 3.54 gears, in the svx other subarus have 3.7, 3.9, 4.11, 4.44 and possibly others.
As to your thought about the front wheel drive fuse, it would depend on if the transmission is the usa type or the vtd, which was jdm and I believe euro I also think Australian market received vtd. No idea where NZ falls in that respect though.

The VTD is a different front to back ratio it is always rear drive 64% with 36% going forward. Putting the fuse in would cause 50/50 lock up.

Re: Intermittent shuddering
 

May car is JDM, the trans is either JDM or Aus/NZ.

I'm pretty sure the Aus/NZ cars got the same VTD as JDM.

I wouldn't have thought inserting the FWD fuse would cause 50/50 lock up. It seems more likely it would cause front wheel drive only. Are you sure about this ?

thanks, Shane

Re: Intermittent shuddering
 

Hi Shane.

Everything that I have studied on the SVX makes me believe that the NZ model is pure JDM, no mods at all.

The Australian model was modified (eg. Glass headlamps, no JDM options like fog lights or fabric interior)

I would suggest you treat your SVX as a JDM model. I don't believe there ever was such a thing as a NZDM. The market is too small.

My SVX shudders too. I believe it is the 'universal joints' on the front/rear end of the diff. I hope to get mine repaired soon.

Merry Christmas, take care.

Mike

Re: Intermittent shuddering
 

No front drive only on vtd I am very sure 50/50 I am reasonably sure of

Re: Intermittent shuddering
 

You don't have a FWD fuse slot, you have a locking fuse slot for the VTD trans that locks it 50/50.
Only the ACT4 cars have a FWD fuse.

Also, if a transmission used was not a VTD transmission, it will not be usable in a vehicle originally equipped with VTD without significant changes. AFAIK, only the SVX and turbo models over there received the VTD transmission. Any others still have the ACT4 transmission.

Re: Intermittent shuddering
 

If its not a vtd trans, you have 2 choices to disable the rear drive. You can install the fwd fuse, or remove the back half of the driveshaft. If you aren't going to be able to get it fixed for more than a couple weeks i recommend removing the driveshaft. I have no experience with vtd, but the act trans is set up to run fwd all the time, and power the rears intermittently.
My 4eat xt6 had a shudder i thought was torque bind, but turned out to be a bad front axle. Your mileage may vary lol

My 2cents worth is, that if its not a vtd, it would have significant issues running with a vtd trans controller (tcu).

Re: Intermittent shuddering
 

You can't run a FWD fuse in a VTD car. It is a diff locking fuse. He has a VTD TCU, therefore it doesn't matter what type of transmission is in the car...
And the VTD trans cannot run in FWD only, even with pulling the driveshaft.

Re: Intermittent shuddering
 

To clarify my own thoughts and to summarise for those who don't want to read the whole thread later.

JDM car in NZ with intermittent drive train shuddering.
Trans has been replaced with a trans from a parts JDM SVX.
Trans code = TZ102YBABA-CF
Dealer tells me this trans is originally from a 1994-96 Legacy.
Safe to assume that both SVXs are VDT (they're both JDM).

Heritage of the ex-Legacy trans is unknown.
Is it VDT or ACT4 ?
Need to know for sure the diff ratio required for the ex-Legacy trans.

Drive ratio for the trans is likely to be wrong for the SVX it has just been fitted to, but the parts car may have had the diff swapped when the trans was swapped. So I need to identify the diff in the parts car.

VDT type car does not have FWD (front wheel drive) only fuse. Instead this acts as a diff lock providing 50/50 front/rear drive.
FWD fuse cannot be used to disable rear drive.

Other suggestions received along the way :
Bad front axle
'universal joints' on the front/rear end of the diff
It may be the inner front CV joints. If memory serves we had an intermittent drive train shudder which was fixed by removing, stripping, regreasing and swapping the CV joints over - left for right

Re: Intermittent shuddering
 

If a vtd trans is not in the vtd tcu could be causing the problem you would need to pair the tcu to the trans

Posted from my phone, so I thought I would clarify a bit.

If the transmission is from a legacy and has the ACT4 You NEED to run the ACT4 TCU as the VTD TCU will cause problems. First problem that I can think of right off hand is the solenoid C function in the VTD the solenoid acts reversed from what the ACT4 does.

I dont remember which way it works, if current locks up the clutches or if no current locks them. I just know that it is different for each. So running a jdm trans with a usdm tcu will cause it to lock into 50/50 just normal driving.

So I am betting that running a vtd tcu with ACT4 will lock up the clutches and that might cause your shuttering as well.

Re: Intermittent shuddering
 

So I need to find out if trans code : TZ102YBABA-CF originally from a 1994-96 Legacy (NZ/JDM) is VTD or ACT4

Any suggestions from the audience ?