What year rear end is this#3899143... A41

[Jim R.]

Hey guys can anyone tell me the year of this differential the main case is casting #3899143 with a date A41 an a CON3 ... I have the cover off and it has 370 gears........ The cover is part # 3830808, i think the cover is a 63 but the case i'm not sure,

[Lynn H.]

Re: What year rear end is this#3899143... A41

Jim,
A quick look at Noland Adams book shows the 63 differential housing to be #3818758 (so yours is sometime after that I would guess). As far as the cover it shows #3830303, so maybe the 8's you see are 3's??
Lynn

[Lynn H.]

Re: What year rear end is this#3899143... A41

Colvins "Corvette By the Numbers", shows the 3899143 casting being correct as follows:
3899143-N: 1967
3899143-NF: 1968
3899143: 69-79 All
Yours appears to have a 1971 date code.
Lynn

[Jim R.]

Re: What year rear end is this#3899143... A41

Thanks lynn.......jim

[Wayne M.]

Re: What year rear end is this#3899143... A41

Jim,
A quick look at Noland Adams book shows the 63 differential housing to be #3818758 (so yours is sometime after that I would guess). As far as the cover it shows #3830303, so maybe the 8's you see are 3's??
Lynn

The 3830303 is a '63 thru early '65 rear cover. if the latter, it may even have a coarse ('65-up) type rear fill plug.

[Harry S.]

Re: What year rear end is this#3899143... A41

The 63 cover used a fine thread pattern on the plug. I believe that all 64 and 65's had a course thread pattern. Looking at the picture, the plastic vent was a 64/65 vent, the 63 vent was metal. Did some 63 vents get into 64 production, probably, same as the fine thread pattern.

[Gary R.]

Re: What year rear end is this#3899143... A41

sounds like a 71 by the code. I would be less interested in the casting numbers and more of what you have inside. If it's an untouched 71 then the carrier(housing),the posi case and spiders are better then the 63-69's. The clutches are pretty weak though. If you're going to rebuild it then it shouldn't matter but if not I would check it good before using it.

[Wayne M.]

Re: What year rear end is this#3899143... A41

The 63 cover used a fine thread pattern on the plug. I believe that all 64 and 65's had a course thread pattern. Looking at the picture, the plastic vent was a 64/65 vent, the 63 vent was metal. Did some 63 vents get into 64 production, probably, same as the fine thread pattern.

Harry -- my experience of the change-over period (based on a sample size of two ) differs. My early '65, the cover you see in the above photo with the plastic vent, is VIN 014xx, assy. AP_9_17_64 [who in his right mind orders 4.11's with air conditioning ? ). This is the one with the coarse thread plug and plastic vent (interior cover pic appears first below).

Second pic is of a mid-64, assy. CF_1_3_64 (yes, 4.56's). It has the fine thread plug (I show both the fine and coarse plugs alongside the fine thread hole). The yellow "swoosh" means it was built for Joe Nike . Just checked and I can see a metal cap on the vent, which I guess means a metal vent.