Wank.a.lot

ok guys
this is not a question about mpg or anyother tranny that would be better.
as a few of you know i'm putting a sbc in my rx7, i just bought a motor and got a free tranny with it.
the tranny is a th400 and according to the kid i got it from it needs a rebuild. when i say kid i mean 17-19 year old kid.

he said that he bought the tranny from a guy that said it was good. he put the tranny in and found out it needed a rebuild.
he says that from a start he would have to give it a lot of throttle to get the truck going.
now my wife had a 70 c10 that was the same way. her tranny had a leak and was low on fluid.
also the motor i got from him is rated at about 200 hp. combine that 200hp with a heavy *** 74 pickup and you will need to gas it a little to get the truck moving.
he said once the truck is going the tranny shifted fine, it just wouldn't start from a stop good.

ok so to my question
this v8 swap i'm doing is going to be done as cheap as possible, but not ghetto rigged. i could rebuild the th400 for about the same price as a used th350. or i could just drop the 400 in and see if it does need a rebuild. or i could buy a used th350.

now i know the gears are different, but not that much different
my rear end is 4.10

th350
1st - 2.52
2nd - 1.52
3rd - 1.00

th400
1st - 2.48
2nd - 1.48
3rd - 1.00

so what should i do
sell this th400 and buy a th350 used
rebuild this th400
or just throw the th400 in and find out if it needs a rebuild



oh and the kid installed the th400 himself and didn't seem to know much about working on cars. i think he didn't refill the tranny all the way after the install.
which could be bad for the tranny.

Smith-02

400 = bulletproof.

350 = a few lbs lighter.


find a 5spd trans from a 4.3 s10. problem solved.

Smith-02

also, get some low *** gearing or find a cheap 8.8" rearend with airplane gears from a f150 if you stay automatic. 4000rpm @ 60mph = not fun

con

I would think the t350 would be alot easier to get to fit in the rx7's trans tunnel. If it was rebuilt with a shift kit it would be way stronger then you would ever need but.........................

bingo

Scott-EP

thats what i was thinking too

Wank.a.lot

i'm either using the 400 or the 350.
no other tranny will be used.
the th400 will fit with no problem.

i should also be at 4k rpm @ 70 mph

i guess i should have asked my question different

are the shorter gears of the th350 that much better then the gears in the th400?
i'm not too worried about the weight of the tranny or with the strenght of the tranny. i'll be blowing rear ends before i blow up a transmisson.

as for a 5 speed trans from a s10, i want to stay automatic. if i was gonna get a manual i'd get the t56 6speed tranny

Smith-02

dude, .04 gearing in low gears in a trans isnt going to make a difference.
get a new rearend. youll thank us later.

Wank.a.lot

does anyone make some cheap rearend gears for a n/a rx7? cause i'm not swapping my rear end for another cars rear end.
seems like the rear end and the th400 tranny will be perfect for the 1/8th mile.

so i guess the answer is to just throw the th400 in.

like i said in my build thread, i'm doing this cheap to see if i like the car or not. if i like it then i will either build the motor or drop in an ls1 and make it smog legal in cali.

Scott-EP

if its between a th350 and th400 then I would go with the 400. That rx7 is light and I bet the taller gears will be better.

Smith-02

there is no taller gear. at 5500rpm with a 235/60/15 tires and stock rx7 gearing, that .04 gearing difference in first wont show a difference in mph vs shift point, secone gear will show 1mph more.
redline speed speed


5500 41 42

3.08 gearing will be:

5500 55 56