Earthworm Can You Explain This???

blacknite · #1 03-12-2005, 10:28 AM

The WRX 5spd has a unique (to Subaru) 1.1:1 ratio AWD system. This gives you a 3.90 front diff and requiring a 3.545 rear diff.

3.545*1.1 = 3.9

blacknite · #2 03-14-2005, 06:48 PM

Or Anyone????. The Reason Is Because, I Been Running My 5 Speed (impreza Trany) With The Stock Rear Differential For A While. I Just Install The Speed Sensor And Notice That My Speed In Very Low At The Fifth Gear. I Try To Replace My Rear Diff. With The One From The Impreza..... And When I Did Some Bad Noises Started Caming From The Trany. So I Went Back To The Stock Rear Diff. If The Trany Was Design For The Impreza Rear Diff. Why I Started Having Problems With It??? ......
With The Impreza Rear Diff. My Speed Was A Lot Better.

Can Someone Explain This!!!!! Thank You

lee · #3 03-14-2005, 07:34 PM

What is it you're asking for an explanation on. The Impreza WRX front diif is 3.9 and the rear is 3.545 driven by the 1.1 to 1 gearing which makes it "look" like 3.9 to the internals that want front & back at the same ratios.

I wasn't aware that "regular" Impreza rear diffs could be used in the SVX - Legacy diffs have the correct diff 5-bolt side plates, the Impreza units (I've seen) do not.

What process did you use to swap between one gear set an another - did you check for proper gear mesh, pinion shims, etc.

blacknite · #4 03-14-2005, 08:08 PM

What I Did Was To Swap The Whole Rear Diff. And Replace The Passanger Side Axel. And It Work Fine Until A Year Latter The Axel Broke From The Locking Ring That Snaps In To The Diff, I Replace It With An After Market One And It Brocke Again. Then I Decided To Go Back To The Stock Svx Rear Diff. And Put The Pass Stock Svx Axel Back Again.....

blacknite · #5 03-14-2005, 08:30 PM

And Just A Couple Of Days Back I Decided To Go Back And Use The Pinon Or Whatever Is Called Put It In The Svx Housing With The Lsd. And When I Did, The Trany Started To Make Noises Real Bad. Why????? If The Pinion Came From It's Matching Trany Why It Did Run Fine. (if It Run With The Impreza Rear Diff). Why It Didn't Run Fine With The Lsd. I Don't Know If I'm Explaining My Self. But Please Reply....

Or Why Does The Trany And Rear Diff. Works Fine On The Impreza
But Just By Replacing The Inside Lsd From The Svx The Set Up Doesn't Run Fine?????

lee · #6 03-14-2005, 10:17 PM

OK, we probably have terms confusion. The ring gear is the large round "ring" that is bolted to the center section inside the differential. The pinion is the smaller gear that has a long shaft extending back from the driveshaft.

Next, as I understand it, the ring & pinion on the Impreza and the SVX are different sizes (see pic in link below, Imprezza on left, SVX on right)

http://www.subaru-svx.net/photos/fil...etkd/19622.jpg

So, the SVX ring & pinion must stay as a matched pair (at 3.545), as well as the Impreza as a matched pair (at 4.11 or whatever).

So I'm still confused on how you swapped in the Impreza pinion into the SVX differential. If just that part was changed the gears would not mesh correctly, causing binding and a noise as the transfer clutches work overtime.

BigBlueSVX · #7 03-14-2005, 10:52 PM

I have a little question related to this topic...

Why is the front diff 3.9 and the rear diff 3.545? I understand that is because of the 1.1:1 ratio, but why aren't the diffs the same ratio? I'm guessing Subaru didn't do this just cause they felt like it

.

blacknite · #8 03-15-2005, 09:04 AM

First Of All When I Did It. I Trnasfer The Pinion Only. To The Svx Assambly. And I Started Having The Grinding Problems In 3rd Gear And Up. So I Figure That The Sound Wasn't Coming From The Rear Differential. Other Wise It Will Be There All The Time... So Have Can I Get The Best Performance Out Of The 5 Speed.... Why If The Pinoin Is Smaller Than The Svx. It Work Fine With The 5 Speed???

lee · #9 03-15-2005, 03:22 PM

The combination of the number of teeth on the ring & pinion give the gear ratio. They must be changed as a set to acheive matching gears between the gear set in the front differential and the rear. If you transfered only the pinion, then the noise from the transmission is due to the transfer clutches fighting differing speeds between front & rear. It probably thinks one end or the other is slipping and it's transfering power to compensate - which just makes the problem worse & noisier.

blacknite · #10 03-15-2005, 04:19 PM

I See Know, So How If I Have 3.99 And 1.1 Plus 3.45 In Rear. And If I Want To Switch To 4.11 In Rear How Do I Do It?????? Change Ring And Pinion When The Ring Will Be Limited Slip And It Will Not Match My Pinion Because Of The Different Numbers Of Teeth. So To Have The Best Of The Performance What Should I Do. ????

blacknite · #11 03-15-2005, 04:30 PM

Here Are Some Pictures

lee · #12 03-15-2005, 05:21 PM

I don't think you can use the 1.1 box and get a 4.11 ratio - I don't know of any gear sets that match to that ratio

blacknite · #13 03-15-2005, 06:50 PM

I Had Finallay Figure Out, I Never Realize About The Ring Part( I Tought It Was The Whole Assambly, But Is Just The Part With The Teeths))). I Tought It Was Just The Pinion That Needed To Be Change. You Are The Only One That Really Payed Attencion To My Problem. And I Beleive That The Traany Can Even Run With 4.11 Because When I Took Apart The Rear Diff. The Pinion Was A Lot Smaller Than The Svx Rear Diff... Thank You!!!!!

lee · #14 03-15-2005, 07:30 PM

you're welcome...hope it works out for you.

Earthworm · #15 03-17-2005, 05:37 PM

Sorry I didn't get in on this earlier as I've been working on my websites.

Hope you got everything worked out.

As for alternate ratios with the WRX tranny...there aren't any that will work other than 3.90/3.545