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Old 08-31-2007, 05:17 AM   #1
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Default Need help! Diff question.

Alright guys I need some help. I own a 94' with a Type 1 torsen and a turbo '99 with the factory open diff. For obvious reasons I would like to swap the diff between the two cars. What is the easiest most effective way to swap these diffs and what all is needed from each car? Can I just unbolt the rearend and swap them or do I need axels and everything? Please help me out and give me a detailed answer. Tom at partsgroup completely rude and told me I need to come buy something before he will answer any questions. I even bought my '94 from him

Edit: It seems I caught Tom on a bad day, he has been helpful to me thus far. Sorry for the misunderstanding.

Last edited by yeah_its_boosted; 08-31-2007 at 03:46 PM.
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Old 08-31-2007, 06:38 AM   #2
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I think you should be able to just swap the meatballs
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Old 08-31-2007, 12:09 PM   #3
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The axles in your '94 are most likely two-piece, whereas the ones in your '99 are single-piece. However the diff itself is the same.

Prise out the axles from the '99 diff. Unbolt the axles from the stub shafts on the '94, then remove the stub shafts from the differential. Unbolt the driveshafts and disconnect the PPF from the diff housings. Remove both differentials as complete units. Removing the PPF from the diff is sometimes easier if you first disconnect it from the transmission and remove the wire harness and ground wire from it, then drop the whole Diff / PPF assembly and dismantle on the ground.

Now, just swap the diffs and reinstall.
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Old 08-31-2007, 12:18 PM   #4
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What's the difference between the one piece vs the two piece halfshafts?
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Old 08-31-2007, 12:31 PM   #5
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One's a single piece axle and one is comprised of two pieces.

The singles also use larger axle nuts at the hub. Like 30mm instead of 28mm or something.
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Old 08-31-2007, 12:38 PM   #6
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Yup. The two-piece is comprised of:

1- A short "stub-axle" that plugs into the side of the diff, and has a round flange on the end
and
2- A long axle that has a CV joint on the inside, the axle itself, another CV joint, and then the stubby portion that goes into the wheel hub.

The inner CV joint of the long axle sits in the flange on the end of the stub axle, and four bolts hold the two pieces together. This is the same as all the 1.6 cars.


The one-piece axle is complete from end-to-end. Basically, the stub-axle portion is simply captive to the inner CV joint, so the axle looks basically symmetrical (both the diff end and the wheel end look similar, though the wheel end is threaded)

Here's a picture of a one-piece axle:
http://members.aol.com/solomiata/singlehalfshaft.jpg

Here's the long half of a two-piece axle:
http://members.aol.com/solomiata2/halfshaft2.jpg
And the stub-axle that it connects to
http://members.aol.com/solomiata/Stub.jpg
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Old 08-31-2007, 12:46 PM   #7
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^ Thanks for the info guys.

One last Q,which axles are stronger,the single or the two piece?
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Old 08-31-2007, 01:19 PM   #8
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Quote:
Originally Posted by spike View Post
One last Q,which axles are stronger,the single or the two piece?
I doubt that it much matters. The CV joints appear to be identical between the two designs, as does the axle shaft itself. In all of the drivetrain-related failures we see around here, the ring & pinion gears tend to be the first weak spot, followed by the transmission itself. It's hugely unlikely that you'll break the axles- something else will fail first.
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Old 08-31-2007, 02:17 PM   #9
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Default okay

so I dont have to use anything but the entire assembly? I do not have to rmove the diff from the housing or anything? Just the entire rear end right?
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Old 08-31-2007, 02:36 PM   #10
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basically what I'm asking is if I have to take apart the diff housing or if I can just plug and play so to speak with the entire assembly. That would be much easier. Also I wonder about the gear ratio of the 94 as compared to the 99.
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Old 08-31-2007, 02:48 PM   #11
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You don't need to disassemble the diff. Assuming both cars have a manual gearbox, then the complete differential assembly (nosepiece with input flange and carrier) can be moved from one car to the other. The stub axles that you prise out from the '94 diff will fit into the '99 diff, and the full axles from the '99 diff will fit into the '94 diff.

While the diffs are out, it would be a good time to replace the shaft seals where the axles plug in. Simple procedure that can be done while the axles are removed without having to disassemble anything.

Determining the ratios can be done rather easily with the back end of the car in the air, the gearlever in neutral, and the brakes off. Using white paint, place a mark on the propshaft or the diff input flange. Also place a mark on the inside of both rear tires, exactly at the bottom. Turn the propshaft by hand while counting the number of revolutions it takes to rotate the wheels one complete revolution (make sure that both rear wheels turn at the same rate.) The ratios are very similar (3.909 vs. 4.1 vs. 4.3) so a high degree of precision in marking and measuring will be necessary to yield an accurate result.

The '94 diff, assuming it came from a manual gearbox car, is almost certain to be a 4.1 ratio. The '99 diff, if it's from a 5-speed, should be a 4.3 ratio. If the '99 was a six-speed, then it should be a 3.909 ratio.
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Old 08-31-2007, 03:04 PM   #12
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Default okay!

Thanks man. Exactly what I needed. So the 99 is a 5 speed so, I wonder what the effects will be of have the slights higher gearing of a 4.10 as compared to the 4.30, I mean on the speedo that is... With 270hp maybe it will lend less wheel spin, lol.
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Old 08-31-2007, 05:04 PM   #13
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Quote:
Originally Posted by yeah_its_boosted View Post
I wonder what the effects will be of have the slights higher gearing of a 4.10 as compared to the 4.30, I mean on the speedo that is.
On my '92 with the original gearing and 23" tires, I found that my speedometer disagreed with my GPS by roughly 7%. Specifically, it indicated roughly 7% fast, so when the speedo indicated 70 MPH I was actually going 65 MPH.

When I replaced my 4.3 VLSD setup with a '95 Torsen (4.1 gears) I found that the disparity between the two roughly corrected the miscalibration of the speedometer. It is now very nearly accurate. I think it may still be 1 or 2% fast, but at this point we're talking about the width of the needle.

The NBs have electronic speedometers, and I suspect that they may be slightly more accurate than the NAs, however bear in mind that we're only talking about a 4.6% reduction in ratio from 4.3 to 4.1. It's not going to be dramatic.
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