aftermarket or stock transmission replacement

[Wiyr]

hey guys, new here and got a 89 suburban 1500 with a 350 in it. 6-8" Suspension lift, with 35x12.50r15 Tires

i got it with a "bad" transmission, all the gears work, but the fuild just pours out after about 6 qts. reverse works, and forward works but in 4-L, and only goes alittle got i cant get enuf fuild in the tranny for the forward gears to work...

well the truck has a aftermarket transmission in it, but i dont know which. the transmission pan is sq but has one of the corners slanted Like The Drawing.. lol
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but im thinking about going back to stock (THM350) but my dad says that the tires will burn the tranny up?

so my question is. should i get the Stock THM350 or get a THM400 or THM700R4
will any of those transmissions bolt up to the 350 engine?
im leaning to the beefer 700R4 but the question bout that is, my truck came stock with the 3 speed THM350 so i dont have no O/D button. but can it be done?

[TheUnit]

Your steering column has 1/2/D correct? If so, in order for the 700R4 to be controlled properly you would need the 90-91 column (1/2/D/OD) and such....

with that said, the 700R4 in my opinion is the better choice even though you would have to invest more $$$ to make it work.....1. super low first gear 2. overdrive 3. 700's last forever and take abuse like a champ (shift kit and valve body works wonders)

[Wiyr]

Your steering column has 1/2/D correct? If so, in order for the 700R4 to be controlled properly you would need the 90-91 column (1/2/D/OD) and such....

with that said, the 700R4 in my opinion is the better choice even though you would have to invest more $$$ to make it work.....1. super low first gear 2. overdrive 3. 700's last forever and take abuse like a champ (shift kit and valve body works wonders)

thanks, all i needed to now, i can probably get both for 300$