ok as my 500+HP 347 stroker gets closer and closer to being done its time to start thinking of what gears in the rear end to use. a little on the car the 347 is going to have just over 500hp my trans is a c4 rebuilt stage3 transgo shift kit and 2500 stall now my rear end is stock for now but I picked up an 8.8 from a 96 expedition and my rear end shop said 31 spline axles and a variety of gears a full spool big bearings all new seals the whole kit and caboodle but I have to decide what gears. I want the car to hook really well on the 1/4 mile but still be streetable without my engine being wound way up in the rpms should I take it on the highway I could care less about gas mileage as I already know its going to be horrible but I dont care well not yet anyway I havent had to fill up the tank two blocks after I just finished filling it up so please tell me what you recommend
okay then another question what stall do you guys think I need? 3500/4500? the transmission was built for the 302 in the car now it was set to handle 500hp it was not built with any specific plan or direction other than to be able to stand the 500hp. the transmission was the very first thing I had repaired as before it was slipping badly
your in a situation of compromise. you need to know the power band of your motor, not just that it will make over 500 hp. you really should know your torque curve and horse power curves to accurately figure out your converter stall speed and rear end gear ratio also we need to know your rear tire height. so with the limited info in would suggest starting with 3.73s or 3.90 gears. you will be spinning over 3000 rpm on the freeway with those. a 347 will need to be spinning a fair amount of rpm to be in its efficiency range to be capable of over 500hp. i would also increase the stall speed of the converter to at least 3000 rpm.
Well I agree also with Bryant sort of. Most 347s have their TQ range from about 3000-5000 rpm +/- 500rpm.Your HP could climb above 6500. Now with that being said I run a 28in tire ,built C4, with a original 8in with spool,and 380 gears. great combo for street or strip.I am now running a 3800 converter.I shift at 6400 and have a 347 too.
Was the converter built for the car/engine combo? Or was it a off the shelf 2800 stall? If it was a off the shelf converter then the stall will probably be higher than advertised. There are a lot of things that effect the stall of a converter. Car weight, gear ratio, engine torque, tire size, etc... I also agree with the 3.73 gears. About the best for all around use.
Bryant nailed it again. I'd also guess that around 3,200-3,500 stall with 3.80'ish gears would be decent enough for street and light strip duty. If you get everything tuned and working well together.. that's a nice solid 11 second street car right there. Then just disconnect the sway bar, uncork the exhaust, adjust tire pressure and go have some.. "I just picked up 4/10'ths".. fun at the track. Another low budget trick is to run some cheap and light 14 inch rims with the biggest cheater slicks you can fit on them. That will give you extra traction while simultaniously shortening the rear gear a bit more for better track time. Just need to tune the minimum tire height for the traps, is all.
good info the stall I guess it was built for a fairly stock 302 when I had the trans rebuilt a couple years ago. the weight would be somewhere in the 3000 range since I plan to have a full interior with a cage with a removable bar behind the front seat so I can actually use the back seat if I wanted. the wheel size have now is a 15" wheel. I plan to get some drag lite deep dish wheels for the rear something like an 8" wide. I will eventually do a mini tub and stuff some big cheaters under it.
