TheSamba.com :: View topic - Difference between early and late Bug IRS?

Wed Sep 02, 2009 8:36 pm

I have a couple of IRS bug trannys at my shop and I would like to run one of them, but Im not 100% sure if there are the early type....how can I tell? Only reason I want an early type is for the 4:12 gear ratio, itll hold me over till I can fix my bus 5 rib. I looked through the trans for dummies thread and still couldnt quite get a clear answer....so maybe one of you can tell me?

Wed Sep 02, 2009 8:42 pm

2 bolt nose cone and dual side plates. is a 4;12

Wed Sep 02, 2009 10:41 pm

towd wrote: 2 bolt nose cone and dual side plates. is a 4;12

Not always.

I have two 3.88 dual side cover IRS trans in the bed of my truck right now. I bought 6 used trans and 4 ended up being 3.88's with two in single side cover and two with dual side cover.

The best way to tell the difference is the alpha-numeric code on the right side of the trans.

A "AH" is a 4.12 and a "AT" is a 3.88.

Wed Sep 02, 2009 11:30 pm

Ok well Im pretty sure they are 4.12s then cuz Im pretty sure they both had AH on them, I have a what I believe to be stock 74 bug tranny which should be a 3.88's in my car right now Ill have to check for an AT on the side, its just to tall for my 31x12.5's....

Thu Sep 03, 2009 10:55 am

yea i have a 3.88 with 31x10.5's and it was pretty tall...but i still made it work. But now i have a 3 rib which is what...a 5.38 or something like that. i cant wait.

Thu Sep 03, 2009 8:01 pm

ok so 1 of my trannys is an early one, it has dual side plates, 2 bolt nose cone and has an AH on the side, the other one is identical but has a DC on the side....anyone know what that is, or is it the same as an AH?

Thu Sep 03, 2009 8:15 pm

Sevnty4Baja wrote: ok so 1 of my trannys is an early one, it has dual side plates, 2 bolt nose cone and has an AH on the side, the other one is identical but has a DC on the side....anyone know what that is, or is it the same as an AH?

DC should be Type 3 IRS, '69+. Same 4.125 final drive. You would really be set if it was a DD (T3 IRS with a limited slip). :lol:

Fri Feb 19, 2010 1:34 am

Does any one know if my type 3 tranny I have with a 4.125 ratio is any stronger than a type 1 4.125 ratio tranny? Cuz I know my 74 tranny is supposed to be stronger(late IRS) than an early type IRS.....

Fri Feb 19, 2010 5:28 am

I bought a 74 super for parts for my baja. It has an AT (3.88?). You said you made it work. Was it OK or should I just sell it and look for another AH (4.12)? Can you change the R&P between these trannys?