rtpassini

should I have any gears changed or switched up while its being rebuilt?
Right now I just dont have the money to redo the rearend right now. its a 2.73 with FULL posi.

I figure if i can switch up the gears somehow, i can offset the high rear end to give me better low end.

this is in a 1980 T/A by the way. Im new to domestic transmissions. so thats why it may be like im asking stupid questions.

fast01

iTrader: (16)

Yes, you can change the gear ratio in the tranny, but it requires a new planetary gear set and it's not cheap. The TH400's factory ratio is 2.48/1.48. You can get a 2.75/1.57 for greater torque multiplication, but again it's not cheap. We're talking more than half the cost of the tranny itself, in the $700-$800 range and should you eventually upgrade your rear gears and add more power, you may end up with traction problems. If you want to get the most out of your 2.73's, make sure you run the proper stall and run the shortest overall tire height you can.

slow67

iTrader: (2)

And the 2.75 gear set is only good to about 800 hp. Don't get the TCI gearset either.

darkhorsebob

That was the old TCI 2.75 gear set. The new 2.75 set has six pinions and a steel billet stand which contains the the six pinion gears. The sun gear is no longer welded, it is splined to a sun gear sleeve. This new setup is as good as any gear set made!

Bob

darkhorsebob

TCI also has a 2.97 1st gear set with a 1.57 2nd gear.

chris718

Sounds like the company has copied JKilgores means of retaing the sun gear.Reversed helix angles on a common sun gear does not work.When the sun gear "screws" the ring gear in first gear with no thrust surface it eats itself up in short order. When they are not connected this is ok.Ill post a photo later of the right way to do it.

chris718

This is the right way to make a sun gear for a 1.57 second gear 400 which gives a 2.75 first gear

chris718

photo of gear