mitch8198

Mismatched F&R diffs, how stuffed is the viscous centre?

By mitch8198, in Impreza, Crosstrek and XV

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mitch8198    62

mitch8198
Posted (edited)

Finally got a v7 dash and a Link G4+ in my v3 wrx and was ready for the dyno.

 

Keith Stewart is doing the tuning so bolted it up and the back hubs spun faster than the front :confused:. He made a good call that there were incorrect ratios going on. Must be when the previous owners swapped to the 4.44 ratio V4 STi box in my parts car, they left the original 4.1 ratio diff in there :/ 

Put a proper 4.44 rear diff in and Keith got it tuned to 180awkw :)

 

He was still having trouble getting it to hold rpm on the dyno, the controller kept getting confused as one minute power was 50/50 and then the next the car starts surging and the front hubs are spinning faster than the rear. We only managed to get a couple proper power runs after 4.5+ hours.

 

My question is, has anyone experienced this before? Given ive done a couple track days with the car like this plus the previous owners kms aswell, maybe the centre diff fluid is so stuffed now it cant even keep them going the same speed.

 

C35hBci.jpg

Edited by mitch8198
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Guest    1,210

Guest
Posted

Yep been there done that. It doesnt work  on a hub dyno you need to swap out the centre then tune it.

 

I have a complete setup housings and centre diff if required. Its just sitting there in case but I do have a spare box as well so no real need for it.

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mitch8198    62

mitch8198
Posted

Thanks evowrx really good to know I'm not the only one. yeah even now I've fixed the ratios his dyno really doesn't like my car haha. 

 

Thanks for the offer, will keep that in mind when I get around to replacing it. (ie before next track day haha)  We managed to get a good enough tune on it for now and the car drives great. First mod should have been a Link :D

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delta    281

delta
Posted
10 hours ago, mitch8198 said:

the back hubs spun faster than the front :confused:. 

 

Mate you actually had a Ford Focus RS, 73 000$ drift car !

You should have left it like that :D

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mitch8198    62

mitch8198
Posted (edited)
20 hours ago, delta said:

 

Mate you actually had a Ford Focus RS, 73 000$ drift car !

You should have left it like that :D

 

Yeeessss it was actually kind of cool on Manfield. wondered why the back kept stepping out: I had the world's cheapest setup for a drift wrx. :P

 

Wish I had a button to turn it back to proper 50:50 awd like the focus..... (for tuning purposes only :D) 

Edited by mitch8198
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Guest    1,210

Guest
Posted

Mine was completely slipping. Jack the front of the car up just off the ground with the handbrake on and see if it will drive the front wheels. 

 

When its first dying you will feel it cornering its like someone gently pulling at the steering wheel while youre turning. 

 

I had 3 different 4.444 boxes on my 4.111 rear only picked up the ratio difference when it went on a hub dyno. I had just replaced the box with the same ratio. Not sure if it shows up on rolling roads or not but I got a tune by GCP with it in the same state.

 

Will corner much more predictably with new centre diff. Dont need to remove box to do it either.

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mitch8198    62

mitch8198
Posted

Yeah, I would never have picked up the last owners mistake without the hub dyno. 

 

I don't feel any change in the handling, on a sealed road shouldn't it just act like an open diff? 

 

Will give jacking it up a crack and have a look :)

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