th400

as far as a manual i dont have a problem with them thats pretty all i have driven since i was 8 years old but i do alot of driving in town and stop signs and red light start to become annoying after a while thats why im really leaning towards an auto.  

Well consider this, the purpose of a tranny is to provide a ratio range between engine and axle to move vehicle. A THM has a ratio range of 2.48 (deepest ratio divided by tallest one) A 700R4 and a range of 4.33 and your SM465 is 6.56 to one. Also a 700R4 has a 3.06 first gear too (vs 2.48 in THM 400) so which one do you think is going to have better low speed response and torque? Lets put is another way, if you compare a THM400 with 4.56 vs a 700R4 with 5.38 your max ratio in first with THM 400 combo is 4.56 x 2.48 or about 11.3 to one. With 700R4/5.38 combo it is 5.38 x 3.06 or about 16.5 to one. In top gear with THM400 your effective ratio is 4.56 x 1 or 4.56 but actually is is closer to about 4.8 or so because converter has 5 to 7% slippage. Now with 700R4 combo you have 5.38 x .7 or about 3.78 and no slippage. So which one is going to get with program a lot better and have best MPG potential too? (are you starting to see why I say a THM400 is yesterdays news and long past its prime?)  

yeah i get what your saying and now im thinking of just trying to find a later model 700r4(the deep first gear is desirable but i wana enter into the local truck pulls and im not sure how it would hold up to the stress). but before i do that im gona put me in a motor(still thinking the BBC) and lift and tires because theres nothing wrong as of right now the sm465 and i can rough it for a little while longer with a stick.  

As long as you axle gears as deep enough to keep tranny well off converter stall when pulling, you are not going to have any problems. I have a 700R4 in a truck I bought new 19 years ago and has close to 190K miles on it that is still going strong. The "trick" to making a serious puller last is strong axle with deepest possible gears because this reduces driveline strain and improves traction because there is less drive shaft torque axle twist in suspension (tendency to lift weight off RR tire at high input levels and why RR always spins first) because less drive shaft torque is needed for same ground effect with deeper gears.  

if i go to 40's ill probably just put in 4.88 gears which im thinking will give me good road manners and good torque.  

It will be a slug at times. 4.88's with 40's is like about 3.55's with stock tires. Not good 4x4 gears. The way you give them power and manors is gear them really deep and use a OD tranny. BTW, a change from a 4.56 to a 4.88 is not really worth the trouble because it is only a 7% change and going from 33's to 40's is a 21% change. Even going to 5.38's is not going to even the score 100% as it is only a 18% change but it is far better than a 4.88 for that tire size.  

well what about 4.88's with 38's? would that still be to little gear with an OD and would a stock 700r4 stand up to that behind about 400hp?  

From 33 to 38 is a 15% change. A up gear to a 4.88 is again only 7%, a 5.13 12.5% and 5.38 18%. Generally when you go bigger and want same performance you want to go deeper (percentage wise) the tire size increase because of increase drag from lift so upgrading form what you have now, (4.56 and 33's) a 5.38 is is better match for 38's than 40's.  As far as tranny living, I cannot stress enough that the way you get a 700R4 to live a long life is gear axle REAL deep because the 30% OD in that tranny lets you run much deeper axle ratios to reduce average tranny torque loads and still cruise nicely. Part of the 700R4 "problem" is it deep first in that wheeler with taller effective gear ratios can still launch better with a 700R4 than a THM400 because the 700R4 has a 23% DEEPER first gear to get it moving better but it also has a 30% taller top gear which will toast tranny is you do not regear properly and play hard. Many seem to never understand why 700R4 fail. It is like axle ratio is not even on the "screen" as a cause for them.  

i get what your saying so i reckon ill find me good 700r4 and plan oneither 5.13 or 5.38 gears when i get a bigger front axle.  

Do as deep as possible with gears. GM axle are limited to 5.38 but Dana axles can go to 5.57 and 6.14 too. A 5.57 would play nice with 40's and a 700R4.  

if ur gonna do pullin you need the deepest axle gears you can get not just the gears that will get you back to stock ratio, but any transmission after the abuse of pulling will wear out quickly but don't worry there are rebuild kits for the 700r4 that can handle up to like 700 hp and some serious abuse now thats a bad ass tranny cuz its got all the beef and an overdrive gear!!  
Solid axle chevys can't be beat!
My dream truck: 73-91 chevy 3500 crew cab srw with dana 60/14bolt, 6 inc long travel lift with KING shocks, 37 inc tires and a 24v cummins diesel, nv5600 and np205

that what i was thinkin about doing. drop in the BBC and when i got to warm it up get a stout rebuild kit. i have thought about rockwells since their relatively cheap compared to a dana 60(a pair of rockwells forabout $1200-$1500 while a dana 60 is around $1000) and run 40's with a beefed 700r4. can't get much better then that.  

The 6.72 ratio of rockwells is nice too  

very true and from what i can figure with that setup it should be pretty streetable.  

Yep with OD it would be