japscrap

I know it's a bit cheeky to be so direct when I'm not a regular contributor but I need pretty urgent help with my diff; Having already done a couple of searches it seems that you're the one who knows about these things but if anyone can point me in the right direction, I'd really appreciate it.

My car's a '98 legacy 2.5 with gearbox #TY753V3DAA. A 'friend' sold me his diff from his '98 WRX but now it's knackered and I suspect it's because the ratio is wrong and sheer wear and tear from his 300+ car.

Can anyone tell me the ratio of the diff that should be on the car?

APIDavid

iTrader: (4)

There's not a lot of info on these transmissions as most of us concentrate on Impreza varieties. You will have to self help yourself.

You can count the teeth on either the old rear diff or your mates one and see what you get.

I suspect that original rear diff was 3.545

Your mates diff is / was probably 4.1:1 or 4.4:1 assuming an import car not a Euro car.

You should be able to decide if the rear diff that he supplied is the same as your original by counting both sets of teeth.

Although if you have run the car any distance with an incorrect rear diff, I expect that the centre diff is now knackered too.

Good Luck, David APi

japscrap

The diff that's now on the car is from an Australian Impreza and it has a sticker with ratio-3.545 written on it. The original didn't have the same sticker but shouldn't it have been written elsewhere else?

Having said that- I don't think the original diff is available to double check but wouldn't you have to be a proper **** to fit it without being absolutely sure? The guy who fitted it was a rally driver and very experienced mechanic.

Ps, where is the centre diff located- don't say inside the gearbox!!

APIDavid

iTrader: (4)

Sorry mate, it is inside the box, BUT you can usually take the back off without taking the box out of the car to change the centre diff.

Many people have gone before your guy, fitting the wrong diff and busting the centre. lt is a common mistake.

Call again if I can help, David

japscrap

Cheers for the help, but I have a late development that might throw some light on my problems- I managed to get my old diff back and (forgive the novice speak) but there's 10 splines on the input yokey and 37 on the big thing.

Is that a ratio of 3.7:1???

911

No.
You need to count the teeth on the crown wheel of the original diff. You can do this by removing the drain or filler plug from the alloy cover, but if the diff is free of the car, remove the cover and mark one of the teeth. Count round the crown wheel, or better still mark a tooth and the case opposite it, also mark the input shaft (where the prop bolts to)
Turn the input slowly counting the turns to make the crown wheel revolve one complete revolution. If the diff is a 3.54 the you will have turned the input about 3 and a 1/2 times

If the diff were a 4:111 then the input would have revolved just over 4 times to revolve the crown wheel the one turn.

APIDavid

iTrader: (4)

Yep sounds like 3.7:1 to me I don't have one, try Grade A Subaru 01663 744114 any of them, even the ladies that answer the phone, know their onions.

I also think that you will have fitted almost anything but a 3.7 out of your donor car, so I reckon the centre diff is goosed and l do have stock of those.

Good luck David APi

PS just seen Grahams response, it could be a 4.1, unlikely in my opinion, but.

Take off the back cover of the old diff and count the teeth on the pinion low down inside that engages with the crown wheel [ the big thingy ] 9 teeth x 37 = 4.1 10 teeth x37 = 3.7