IRS Transmission code help

[Buggytime]

I just picked up an IRS transmission and it has the following code on it:
38
113 301 103
J
VW
AH4010755

I was wondering if anyone can tell me what the 38 and the J stand for.
I have researched the codes, and I believe it is a 4.125 gear ratio.
It also has two sideplates on it, which I remember someone telling me in the past that it means it's a 4.125 ratio.
The guy I bought it from said it came out of a '73 Super Beetle.
Are these good strong trannys?  Or are the 3.88 gear trannys more durable?  I have a street buggy with a tired tranny, the 3rd gear slips when I drop it into 3rd.  And not to mention a couple other flaws.

And here's the dumb question, the trannys use 80-90W gear oil right?

Thanks

[Geoff]

80-90, yes

the 3:88 trans has a stronger 9tooth first gear and main shaft, the 3:88 is also a stronger ring/pinion but it's geared taller. For off road the 4:12 may work better.

[Buggytime]

Would it be better to have my current transmission repaired, rather than taking my chances on another used one?  I think it might need a new input shaft bearing, and perhaps getting the 3rd gear welded.  If anyone is interested, please let me know.
Thanks

[Bruce]

I was wondering if anyone can tell me what the 38 and the J stand for.

Insignificant casting numbers

It also has two sideplates on it, which I remember someone telling me in the past that it means it's a 4.125 ratio.  

Not necessarily.  I've seen double side cover IRS with 4.37, and with 3.88.  Most common is 4.12.

The guy I bought it from said it came out of a '73 Super Beetle.

It may have been in a 73 Super at one time, but that's not what VW put in a 73 Super.

Are these good strong trannys?  

Probably strong enough for what you're going to do with it.

the 3rd gear slips when I drop it into 3rd.  

Check your clutch first.

the trannys use 80-90W gear oil right?

sure.

[Buggytime]

Thanks Bruce, but I am assuming that it's the 3rd gear in the tranny because I can drop it hard into 1st and 2nd gear without any slipping, so I think the clutch is good even though it's stock.  And I'm not sure if this matters but the motor is a 1968cc.