Brumby WRX conversion, tailshaft vibration

chinski · Post by **chinski** » Fri Nov 15, 2013 4:09 pm

Hi guys, my brumby is running 2001 STI Forester running gear (same as MY00 WRX ) with Auto trans.

it has 1 piece tailshaft with Mazda rear uni bolted to a '92 liberty diff, the vibration comes on about 100kph & is enough to make anything in the mirrors just a blur !! the vibration came & went at random & sometimes wasn't to bad, when i checked the rear uni there was some movement there.

i took it to a local Subaru workshop who are familar with WRX brumbys & they fitted a new uni but now vibration is slightly worse & there all the time ( doesn't come & go like with old uni)

they said the tailshaft has not been made correctly by the guy that did the WRX conversion & i need a L series auto 2 piece tailshaft & then that may need to be modified to fit.

i'm keeping my brumby long term so i would like to fix this vibration properly.

does anyone have any knowledge on if this is the way to go or what else i could try ?

cheers

chinski

RSR 555 · Post by **RSR 555** » Fri Nov 15, 2013 4:35 pm

Highly recommend the 2 piece shaft in the Brumby. To make the one piece that long, the pipe has to be very large in diameter to stop the flex/wobble.

There is a few ways to make the 2 piece fit and would recommend you fit mounting plates with welded nuts under the vinyl/carpet (held down with some sikaflex) then make support bar under the car to hold the centre bearing.

I'd also reccomend you check all rims, tyres, brakes, wheel bearings and steering joints for any play.

ktmtragic · Post by **ktmtragic** » Mon Nov 18, 2013 7:35 pm

Has the shaft been balanced?

RSR 555 · Post by **RSR 555** » Mon Nov 18, 2013 10:31 pm

No one will balance a longer tail shaft (not in WA anyway) as these are too unsafe on the balancer machines. This is what I've been told and I've ask quite a few places in Perth

chinski · Post by **chinski** » Fri Nov 22, 2013 10:51 am

i dont think it has been balanced, with old uni vibration would come & go whereas a tailshaft balance problem i would think would be constant ?

mechanic said even new uni has play because shaft hasn't been made properly, but (same as your recommendation RSR 555 ) 2 piece was only way to go to fix it completely, he is familiar with ej20 brumby conversions as is the workshop owner who says the same

sounds like a 2 piece is the answer then i'm keen to do as mention by you RSR555.

next question, what tailshaft do i need to source ? wrx auto ? l series auto ? mix of both?

chridk · Post by **chridk** » Mon Dec 02, 2013 1:47 pm

chinski wrote:i
next question, what tailshaft do i need to source ? wrx auto ? l series auto ? mix of both?

I used a mix of both and it bolted straight in = L series front half (manual) and 97 wrx rear half (manual). The reason I state the year model for the wrx is that some models don't have a bolt up flange in the middle.
I'll try to get some pic's on the hoist this week.

Edit....I'm running a manual STI box, not auto

Cheers

chinski · Post by **chinski** » Tue Mar 25, 2014 2:39 pm

Still struggling to get this sorted, taken it to a Driveline specialist shop now to get my 1 piece made into a 2 piece, max cost $600 they said....

Now say maybe can't be done as diff is offset & no where to mount a carrier bearing, shaft has been balanced but no help the angles are to far out !!

the shop is going to talk to some engineers & see what they say but they reckon i'm looking at big money.

surely it can't be this hard, will a manual WRX tailshaft fit or something, i want to keep the brumby & have it running smooth but getting pissed with it now.

steptoe · Post by **steptoe** » Tue Mar 25, 2014 5:58 pm

a long time ago someone in this forum said that the last rear wheel drive Mazda 626 had a centre bearing bracket that was a bolt out of Mazda and make to fit Brumby for a tidy centre bearing mount. May be worth investigating. I know I always think of this when I see these old 626's - anywhere

ktmtragic · Post by **ktmtragic** » Tue Mar 25, 2014 8:08 pm

Get the shaft be it 1 or 2 piece balanced First and then fit it. I have had gear done for not a lot of money here in Sydney

chinski · Post by **chinski** » Wed Mar 26, 2014 7:55 am

cheers guys, do you think a 626 tailshaft will take EJ20T power or will it turn into a pretzel ? can't find any online but found a few WRX / Forester / Outback ones with carrier bearing & some from Autos, need to find some in local wreckers & take my 1 piece out & go & do some measurements i think.

the one piece has been balanced, made no difference to vibration but will get a 2 piece balanced to if i can ever get one in.

Proton mouse · Post by **Proton mouse** » Wed Mar 26, 2014 11:48 am

As soon as I started reading this thread I thought of pinion angles being out of phase.
I had a V8 Torana that had a bigger stronger diff (9 inch) fitted plus a 3 inch beefy tailshaft, but it had a very bad vibration at
certain speeds and revs.
It turned out to be the pinion angles, the fix for which was adjustable upper rear trailing arms (which could
pivot the diff up or down a few degrees)
Was perfect after fitting them.
Problem here is that we don't have upper trailing arms on our Brumby's. Im thinking there might be a way though, with shims/washers at diff end
or maybe raising/lowering the gearbox X-member/mounts?? It is a very important angle often over looked with conversions.
Below is a pic to help it all make sense. Hope it helps.

John.

chinski · Post by **chinski** » Wed Mar 26, 2014 12:46 pm

Thanks for that John ill have a look at what I can do in terms of alignment when I get the car back from the shop, they wanted $1600 to make a 2 piece, obviously I have said no .

They found the rear RH inner cv needs replacing so I'm doing that now but I very much doubt it'll have any effect on my "bad vibes" .

chinski · Post by **chinski** » Wed Mar 26, 2014 9:18 pm

Well shop phoned back & they don't have the CV they phoned me to ask if they could put in, and they can't get one...

I do as much work as I can on my cars / bikes but know when to farm it out too, I can't balance tailshafts or shorten / lenghten them ( properly ) so thought I was going the right way, after 2 days in the shop & no work done this is one I'm tackling myself.

Going to check alignment as John suggested, then next step source a 2 piece myself & ***n make it work !!!!!!!

c'mon lil brumby be nice !!

Post by **TOONGA** » Fri Mar 28, 2014 9:37 pm

When we put an EJ box into my brumby we used a 2 piece shaft with a centre bearing the front half was from a manual liberty (1992 I think) and the back half was from an impreza, we changed the diff flange to an impreza one to suit the tailshaft. As well we had to make a mount for the centre bearing one day I will make a better one

Some where in the Subie boys threads there is a really good way to do it

found it showthread.php?t=14686&page=2

the only gearbox/driveline vibration I get is from a stuffed unijoint in the front part of the tailshaft which one day I will replace.

TOONGA

chinski · Post by **chinski** » Sat Mar 29, 2014 9:34 pm

wow that is one impressive crossmember !

alot of work in it but to have it in & running smooht would be worth it, not sure i'm up to building one of that quality but could use the bent RHS idea somewhat i think.

fitted 2 new rear CVs both on right hand side as others were worn in the splines, one shop could not find any, next shop no problems fittted 2 new CVs onto my shaft for $245, this has slowed the vibes but not fully.

also fitted new rear shocks as others were extended ones for when car had a lift kit & rubbers are all flogged out, shocks made a huge difference !! not to the vibration but to general driving, rear end actually moves now & no clunking !!

both unis on my 1 piece tailshaft have a fair bot of play & i found a wheel weight in my driveway off the brumby too so going to sort unis & get wheels rebalanced & hopefully that buys me some time while i head for the 2 piece.

cheers for the replies !!

Post by **TOONGA** » Sat Mar 29, 2014 9:51 pm

Yes they do impressive work

there is this way as well

showpost.php?p=200727&postcount=3

You just need an wrecked L series

TOONGA

chinski · Post by **chinski** » Sun Mar 30, 2014 8:39 pm

That look easier ! still i only have a stick welder so would have to pay someone else to do it, could maybe bolt in something similar.

would need to get it all pretty straight first go though !!

tony90 · Post by **tony90** » Fri May 09, 2014 2:34 pm

Have you checked the front and rear diff are the same ratios?
I got a flat tyre on my Brumby with a WRX 4.44 diff and 14 sunraysias and fitted a std 13 wheel on the rear and the vibration was that bad from the viscous centre. Tailshaft was rattling that bad I thought it was going to fall off. I was running it RWD only.
The centre diff in a manual gearbox is also a viscous type which I assume will do the same thing