Author Topic: Rear gears for 77 trans am?  (Read 210 times)

Bscheit65

  • Active Forum Member
  • *
  • Posts: 91
Rear gears for 77 trans am?
« on: February 04, 2019, 11:47:25 PM »
Does anybody know what most 77 trans am 400 6.6 had for a rear gear ratio gonna change it too 323 think it has 273 but not sure anyone know for sure off top there head? Thanks

Aus78Formula

  • Oracle Forum Member
  • *
  • Posts: 8751
Re: Rear gears for 77 trans am?
« Reply #1 on: February 05, 2019, 07:02:29 AM »
It'll only be a guess until you check. If not sure then what better way than giving an oil change, no messing around jacking up and spinning wheels and counting.

1979 Black and Tan

  • Active Forum Member
  • *
  • Posts: 367
  • '79 in Sunny San Diego
Re: Rear gears for 77 trans am?
« Reply #2 on: February 05, 2019, 12:37:23 PM »
it's stamped on the rear end housing
1979 Trans Am
100% California Car, originally Atlantis Blue/ Black...All Original Unmolested 403, TH350, 2.41
63,300 orig. miles
1971 Chevy K20 4x4

roadking77

  • Oracle Forum Member
  • *
  • Posts: 8275
Re: Rear gears for 77 trans am?
« Reply #3 on: February 05, 2019, 05:33:12 PM »
I think its marked on the pass side tube kinda facing towards the front. May be a lettered code.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

Bscheit65

  • Active Forum Member
  • *
  • Posts: 91
Re: Rear gears for 77 trans am?
« Reply #4 on: February 06, 2019, 01:01:50 AM »
I looked both those places and still couldn’t find anything let you know what I find out putting 323 gears in it

Re: Rear gears for 77 trans am?
« Reply #4 on: February 06, 2019, 01:01:50 AM »

Aus78Formula

  • Oracle Forum Member
  • *
  • Posts: 8751
Re: Rear gears for 77 trans am?
« Reply #5 on: February 06, 2019, 01:17:03 AM »
I'd find out what they are before you swap them or you have based the decision on nothing.

roadking77

  • Oracle Forum Member
  • *
  • Posts: 8275
Re: Rear gears for 77 trans am?
« Reply #6 on: February 06, 2019, 08:09:06 AM »
Did you scrape the tube down good and clean all over. From what I recall its not real obvious until you do some scrubbing. Someone had a chart (maybe butler) that had the codes to decipher the marks. I think there is a date code as well. I'll go out on a limb and say an "s" mark is for the 2:73, but dont hold me to it.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

Aus78Formula

  • Oracle Forum Member
  • *
  • Posts: 8751
Re: Rear gears for 77 trans am?
« Reply #7 on: February 06, 2019, 08:11:52 AM »
It's in every Service manual too. A 2.73 ratio Posi would have 2PU.

Bscheit65

  • Active Forum Member
  • *
  • Posts: 91
Re: Rear gears for 77 trans am?
« Reply #8 on: February 10, 2019, 11:31:14 PM »
Yeah I scrubbed it good with a wire brush still couldn’t find anything ended up opening it up it was a 2:41 couldn’t believe how low that was didn’t know they had that!

b_hill_86

  • Active Forum Member
  • *
  • Posts: 178
Re: Rear gears for 77 trans am?
« Reply #9 on: February 11, 2019, 12:05:02 AM »
Keep us updated or at least me lol. My 77 has that gear or the next up but smaller than 2.73. I’ve been debating 3.08 or 3.23 with my 4 speed. Really leaning to 3.23. Almost picked up a complete 3.42 axle since price was right but I didn’t wanna go that size.
-Brian-

1977 Trans Am 400 4 speed

Aus78Formula

  • Oracle Forum Member
  • *
  • Posts: 8751
Re: Rear gears for 77 trans am?
« Reply #10 on: February 11, 2019, 03:08:21 AM »
That was lucky you checked. Goes to show you can't swap gears simply by guessing what it might be and then jumping a step or two whichever way you prefer. By the way, that's a 2 series carrier which only allows you to go 2.56, 2.73 and up are 3 series.

Bscheit65

  • Active Forum Member
  • *
  • Posts: 91
Re: Rear gears for 77 trans am?
« Reply #11 on: February 11, 2019, 10:29:13 AM »
Yeah I’m still gonna get 3:23 just have to save up a little more money I just need a different carrier since it’s not  273 or above which cost about $500

Ryoko

  • Active Forum Member
  • *
  • Posts: 444
Re: Rear gears for 77 trans am?
« Reply #12 on: February 11, 2019, 05:20:02 PM »
I changed my 74 from an auto to a 4-speed, but left the 3.08 rear end alone. It worked out very well for me and made for a nice cruiser.

Bscheit65

  • Active Forum Member
  • *
  • Posts: 91
Re: Rear gears for 77 trans am?
« Reply #13 on: February 12, 2019, 12:45:13 AM »
That is an option I’ve been playing with is converting to a manual

Re: Rear gears for 77 trans am?
« Reply #13 on: February 12, 2019, 12:45:13 AM »
You can help support TAC!