I just found a wrecked 94 300ZX n/a with the rearend intact for a REAL good price, AND there's no need to provide a core (big sticking point, since I may want to return to stock). However, I have this recurring nightmare of going through all the hassle of the swap, only to find that the donor car itself had a swap at some point in its life, and that it's not the coveted 4.08 ratio R200.
I recall back in my musclecar days how to easily determine the rear ratio by turning the rear wheels and counting driveshaft revolutions (?) - Is this correct? Any other tips and tricks?
I'll copy this to the Z forum as well...
Identifying rearend ratios...
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Und3rprshUr
- Posts: 570
- Joined: Sat Oct 19, 2002 5:53 am
- Car: My 300Z
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Und3rprshUr
- Posts: 570
- Joined: Sat Oct 19, 2002 5:53 am
- Car: My 300Z
The ring gear actually has the ring and pinion tooth #'s stamped into it -
For example:
49/12 = 4.083636 (stock ratio)
47/12 = 3.91666 (J30 ratio)
48/11 ('JDM' 180SX diff, 4.36:1 ratio, 5-bolt output flanges)
The ‘90-‘96 300ZX N/A diff ...
First thing:
DO NOT get the twin turbo diff, as it uses an R230V which is physically too big to work, and it's got a much different gear ratio (3.6X:1). The non-turbo has the same ratio as the 240 (4.083:1). The biggest problem with the 300ZX diff is that the output flanges are different (but the same as the early J30 differentials). They look like a '5 star' flange where the 240sx uses 3 sets of 2 holes. The parts to convert a 300ZX diff to work in a 240SX can be had for around $200-300 new... You have 2 options: Different output shafts, or different axles (i.e. early ['92-94] J30 axles)
You’ll need the output shafts from either the ABS equipped 240SX w/LSD, or the ones from a ’95-96 J30 LSD (same part).
Or you can use the axles from the '92-94 J30 with the diff, as they have the same ‘5 star’ bolt pattern but the correct length, splines count, and axle nut.
The 300ZX diff is the same size as your stock open diff b/c the Z uses 4-channel ABS, meaning the sensor is on the sides as opposed to the J30 with the sensor on the snout - so if you are really worried about the negligible extra length (see below), find the Z32 diff and convert it.
For example:
49/12 = 4.083636 (stock ratio)
47/12 = 3.91666 (J30 ratio)
48/11 ('JDM' 180SX diff, 4.36:1 ratio, 5-bolt output flanges)
The ‘90-‘96 300ZX N/A diff ...
First thing:
DO NOT get the twin turbo diff, as it uses an R230V which is physically too big to work, and it's got a much different gear ratio (3.6X:1). The non-turbo has the same ratio as the 240 (4.083:1). The biggest problem with the 300ZX diff is that the output flanges are different (but the same as the early J30 differentials). They look like a '5 star' flange where the 240sx uses 3 sets of 2 holes. The parts to convert a 300ZX diff to work in a 240SX can be had for around $200-300 new... You have 2 options: Different output shafts, or different axles (i.e. early ['92-94] J30 axles)
You’ll need the output shafts from either the ABS equipped 240SX w/LSD, or the ones from a ’95-96 J30 LSD (same part).
Or you can use the axles from the '92-94 J30 with the diff, as they have the same ‘5 star’ bolt pattern but the correct length, splines count, and axle nut.
The 300ZX diff is the same size as your stock open diff b/c the Z uses 4-channel ABS, meaning the sensor is on the sides as opposed to the J30 with the sensor on the snout - so if you are really worried about the negligible extra length (see below), find the Z32 diff and convert it.