heednfactor

hello everybody complete forum newbie here, please help though i have just changed my wrx gear box and rear diff now when i turn on full lock the back wheels lock up a bit and judder, does any one know if when you bolt prop back to rear diff it has to go on a specific way, i have just spent the whole weekend fitting a new gearbox and diff and am very frustrated,
any help would be greatly appreciated, thanks mike

Splitpin

Welcome to the forum.

There isn't a "special" way to put the propshaft back on, it's as obvious as it looks so that is unlikely to be the explanation.

The one obvious thing that springs to mind that is reasonably consistent with these symptoms is the possibility of the rear diff final drive ratio being mismatched to the front diff and dropgears in the gearbox. Did you buy the box and diff as a complete set from a reputable source, and are you therefore certain they are compatible with each other and, just as importantly, working properly?

Might help us understand a bit more what might be going on here if we knew what exact type and model year your "WRX" is, and also why you were making this change in the first place. Did the old gearbox break, or...?

heednfactor

hello splitpin thanks for your reply buddy, sorry for my lack of info,

here is some more detailed info, my car is a import 1993 subaru impreza WRX SALOON,

i have fitted a new diff and gearbox over the weekend as my second gear stopped working, i found a gearbox through ebay which came from a 1997 wrx the chap told me that it was a short shift close ratio box he said i might need the diff aswell but at the time i only had enough money on me for the gearbox, my brother and i fitted it saturday and when we finished and tried to go for a test drive the rear wheels turned for about 5 yards then locked up intermittantly this was in a straight line and the same happened in reverse so i went no further then i rang the chap who i got the the gearbox from and he said that because it was a short shift i definately need the diff as there was differences between the gearbox and my diff ratio,

Ok so i picked up the diff and installed it yesterday i filled it up with the right oil and right amount, then lowered the car and went for a test drive, the first thing i noticed was when i pull away it is all juddery and feels like theres something holding it back and when i come down the gears its juddery also, then i went to a big car park and tried doing circles on full lock and it feels horrible you can hear the rear wheels locking up intermittanly and skipping. but when your in boost in a straight line it kinda feels ok,

Today contacted the chap that sold it all to me and he assured me that this was all good and i remember him telling me i could test drive the gearbox in the car it came from i declined as time was a issue but it kinda makes me think that he was telling the truth that everything was ok, anyway he asked me if the diff was lined up ok on all mounts and i said yes then he said "you might have wound the diff up and to unwind he said undo the prop and rotate both front wheels backwards whilst in first gear" has anyone heard of this.

hope this info helps thanks

The Zohan

Would be where my money is as well.

Splitpin is very knowledgeable and well worth listening to his advice

Welcome and good luck getting it sorted.

Splitpin

As a matter of interest, have a peek at the top of the bellhousing next to where the starter motor fits, and see if you can see a paper sticker with a code on it that begins "TY752....". If you do, tell us what the code is. Also have a look at the ID plate on nearside front suspension turret under the bonnet and tell us what transmission code was originally fitted to your car.

Yes, it's highly likely the ratios were mismatched. Trouble is that it sounds like they still might be.

It'd help us to know the transmission codes as I asked above but what you're describing could be caused by a broken rear diff, broken centre diff in the new box, or, given that the symptoms are similar (albeit less pronounced) with the new rear diff than with your original, it sounds possible that there is still a front-rear reduction mismatch.

Blimey. That's total f'ing bullsh*t. The phenomenon of diff wind-up is certainly a real one (and you may well be suffering it here) but the idea of "un-winding" it like that is a joke.

Without knowing who the vendor of this gearbox is, I would be reluctant to trust anybody who comes out with a story like that.

It may well be that the box and diff are good. It may also be that one or both was fecked before you bought it. It may also be that the vendor has accidentally given you the wrong rear diff, while it's also possible that they were running mismatched (and were juddering in a similar way) on the car they came off, but that the vendor is too mechanically unsympathetic to notice.

If you can get us a transmission code off the new box, you will have to take the inspection plugs out of the rear diff and physically count the teeth on the crownwheel and pinion in order to determine the final drive. Then at least you should be in a position to determine whether there's a ratio mismatch.

If it turns out there isn't, the obvious conclusion to draw is that the gearbox is damaged. Whether you want to go through all that first, or contact the vendor and see what he has to say, is up to you/

heednfactor

Hello guys thanks for your input so far due to work commitment I havnt been able to get to the wrx but I remember the vin plate code for gearbox ended in 3aa, and late lastnight I went to shops and put my foot on the clutch there was a clunk then the pedal went to the floor and stayed there I think the clutch fork did not locate on thrush bearing fully and has popped off (my bad) does anyone know If you can relocate it without undoing the bell housing, thanks mike