on the rear LH brake drum is the stamping: KH 8 74439 and on the differential case is the stamping: J 098 979 05 on the axle tube is no stamping. the axle is mounted on a 69 firebird with 350cui and TH400 automatic. Which rear axle is this? I didn´t found it in the service manual.
Sportsman, Did you check out the location on the axle that I show on this web page? I assume the 69 has stamping similar to the 68. http://www.geocities.com/jims68fb/AxleCode.html The stamping is very faint and hard to see. If the axle is old, rusty, and dirty it's real tough to see.Jim
Is it a 10 or 12 bolt rear? 10 bolts were installed in Firebirds and 12 bolts were installed in other GM products. If you have a 12 bolt it's not original. If you want to know your "rough" gear ratio you could always mark the rear wheel and driveline. Rotate the driveline 1 turn, count how many times the rear wheel turns. This is your "rough" gear ratio.
Also, the donor car where I got my 68 Pontiac 350 engine had the stamp under the hard brake line on the axle. This wasn't detected until the rear axle (and brake line) were removed. He hunted for the ratio forever until he actually removed the line and there it was.
I have a 69 w th350, 2.56 rear...was told to check my no. and where ,but I couldnt find it! later took it by a friends house, he located it ,excactly where they told me to look....its very hard to see....maybe use sandpaper or something to clean it up...leaving dirt in very faint indentations...mine was about 4"-6 " out from drivers side brake drum, facing straight back.... its a 2 letter code...
it´s a 10 bolt. the gear ratio should be a 3.55. the wheel turns about 3 1/2 times while rotating the driveline 1 turn. i will look again on the axle tube tomorrow, may be there is a stamping under the hard brake line.
And "sportsman" ,it sounds like its not 'original' anyway, but rear axle could be...th400 were on 400`s ,not on 350`s.... I have a 400 w a th350, just the opposite...
Checking the number of turns between the wheel and the driveshaft can be misleading.
First of all, the driveshaft should turn 3-1/2 turns while the wheels turn once. Not the other way around. But this will only be true with a limited slip differential! (Posi.)
If the rear end is an "open" style differential, one wheel will turn twice as many times as the gear ratio, while the other does not turn.
The best way to check an open (non-posi) gear ratio is to jack up ONE wheel of the car, put the transmission in neutral and turn the raised wheel through TWO revolutions while counting the number of revolutions of the drive shaft. (This is a lot easier with a helper.)
If the driveshaft goes through 3-1/2 revolutions, then you will indeed have 3.55 gears.
If you have a limited slip differential, raise both rear wheels and rotate them through one revolution while counting driveshaft turns.
Jim, on mine it was closer to the left , more like where your red left diag. line crosses the center of the axle... Best way to find mine was to smear some spit from your finger on the axle... mine was built at Lordstown , early production 69, 4th week of oct...(it has the 68 style vents in the dash, which was 'early' prod. too)
As long as you're laying under the car turning the driveshaft, turn it enough times to turn the wheel 10 times - easier math and better accuracy! Mine turned 32 1/3 times to tell me I had a 3.23. My arm got pretty tired, though.
One thought: if the car came with A/C it will have an axle ratio of no more than 3.36. If it has no A/C probably had no steeper than 3.55 ratio. I don't see a 350 HO having a gear ratio more than 3.36, but could be wrong.
questions and/or statements which may relate to finding out if this is original.
the '69 axle tubes were flattened on top for a few inches along the tube. the 67-68's were not. were there any other cars which had these flat spots? does the rearend in question have these?
some of the early cars (possibly only '67) also had eylets welded to the tubes for the swingarms on coilspring cars.
the KH on the drum i do not see in the online manual, but i also don't see an SP code for a 350 with a turbo tranny, so the manual, although indispensible, is fallable. (i have also found other part #s in that manual which are different, or dont seem to exist) and apparently you could order these cars just about any way you wanted them.
anyway, i do see an XH for a 3.55 gear. maybe the part of the X is worn on the drum stamping?
Sixstarved, interesting bit of info on the flattened area on the axle tubes. Mine has that. My bird is a 67 vert and I knew the rear was replaced because it is missing the traction bar mounts. Does that mean it is a 69 firebird rear end?
according to my info, the 69 bird had the flats, and the 67-68s did not.
i also have a 69 rear in my 68. i swapped them myself, and was intrigued by the flats, so have paid attention to what i read about them, and can only relate thusly.
My 69 had a 2:56 10 bolt open. in 1989, it went chunk, and I located about the same raito 10 bolt posi. Later, in 1981, I had an old rusted out 64 Chevelle Malibui Convertable that was on its last legs. A guy I worked with wanted the rag so bad that he could taste it. (Other than horse trading, I won't discuss how I got the rag, but I din't have a dime in it.)
Anyway, the guy had a 12 bolt posi from a 71 Nova, and he gave me the rear and $300 for the rag, and my 10 bolt posi. That was a **** good deal for me because those 12 bolts were gettin pretty scarce in those days. I've had the cover off three times, and there are no numbers on the gears. I tried counting the teeth, but along with spelling challenged, I'm also numerically challenged.
I did the ol spinner' roo and have determined it's either a 3:23 or 3:25. I had one of the best front-end, rear-end man in the industry go over the rear and asked him what was the raito. He, too, isn't that bright at computating numerals. (Your better professional mechanics aren't good at such things. The crooks are because they specailze on figuring how much they can screw you out of.) The guy ended up doing the spinner 'roo, and his guess was 3: 23 or 3:25.
The 12 bolt looks good under the car, and lots of people don't know that first generation Firedogs didn't have the 12 bolt option. So I don't bother to tell them it's not correct. I just say um-huh when they say "Wow! That's a 12 bolt! Is it posi?"
