Drive train suggestion

[englewoodcowboy]

With overdrive 4.56 for 33s and 4.88 for 35s minimum. Buddy has 4.88 with 35s and a warm 351 and he wishes he had 5.13. the overdrive puts the rpm too low on the freeway he says and he wishes 1st was quicker to take off from a start.

Not to troubleshoot your buddy but if he has 4.88 and 35's if he is running an AOD he should be turning approx 2200 rpm at 70mph, if he us running a 4R70W he will be turning about 2300rpm at 70mph. For most cams and a SBF, this is the ideal place to be, no searching etc. if the motor is built for the bronco. I have however seen guys insist on big number engines (that don't produce but 100hp at 2000rpm yet they are pushing 500+ at 5000rpm) that the motor is simply cammed wrong and those big numbers they brag about they will never actually be able to use or see in the bronco. The key is finding a combo to give max torque at low rpms, for example, my 347 is running 400hp and 425tq. My torque is all in at 2800 rpm and my max hp is all in at 3400rpm. Sure my motor is capable of much more HP if we changed cam and intake but I am not driving 1/4 mile at a time so that would be useless other than to say it could do 600 but I would never see or be able to use it. The toughest part people forget to look at is what the engine produces down low and they will be shocked to see they are driving around on less than 100hp most of the time.

To the OP, if you are torn between tire size, I can tell you from experience if you are thinking 35's possibly and you go 33's, 9 times out of 10 you will be upgrading to the 35's just because. If you are wanting to run an electronic transmission, look at the 4R70W and go with 4.88's. They will work for either tire combo well providing you have a motor designed around low end torque. One of our favorite cams is the 5.0 HO cam out of a mustang or equivalent. For a solid build engine they have the broadest range of torque that most customers have been completely tickled with and their bronco is a night and day difference from the stock engine.

 

[68ford]

Not to troubleshoot your buddy but if he has 4.88 and 35's if he is running an AOD he should be turning approx 2200 rpm at 70mph, if he us running a 4R70W he will be turning about 2300rpm at 70mph. For most cams and a SBF, this is the ideal place to be, no searching etc. if the motor is built for the bronco. I have however seen guys insist on big number engines (that don't produce but 100hp at 2000rpm yet they are pushing 500+ at 5000rpm) that the motor is simply cammed wrong and those big numbers they brag about they will never actually be able to use or see in the bronco. The key is finding a combo to give max torque at low rpms, for example, my 347 is running 400hp and 425tq. My torque is all in at 2800 rpm and my max hp is all in at 3400rpm. Sure my motor is capable of much more HP if we changed cam and intake but I am not driving 1/4 mile at a time so that would be useless other than to say it could do 600 but I would never see or be able to use it. The toughest part people forget to look at is what the engine produces down low and they will be shocked to see they are driving around on less than 100hp most of the time.

To the OP, if you are torn between tire size, I can tell you from experience if you are thinking 35's possibly and you go 33's, 9 times out of 10 you will be upgrading to the 35's just because. If you are wanting to run an electronic transmission, look at the 4R70W and go with 4.88's. They will work for either tire combo well providing you have a motor designed around low end torque. One of our favorite cams is the 5.0 HO cam out of a mustang or equivalent. For a solid build engine they have the broadest range of torque that most customers have been completely tickled with and their bronco is a night and day difference from the stock engine.

All I know is that he says being at low 2000s rpm around 65 means it has to down shift more than he likes if there's a hill or if he wants to accelerate. I am merely passing on 2nd hand personal experience.
2nd there is NO WAY you have a naturally aspirated or pump gas 347 make 400hp at 3400 rpm maybe 5400rpm

 

[Broncobowsher]

If you are making 400 HP at 3400 RPM, that is 618 Ft-Lb torque at 3400 RPM.
Math is pretty simple. HP = Torque x RPM / 5252. Well known equation.

 

[68ford]

If you are making 400 HP at 3400 RPM, that is 618 Ft-Lb torque at 3400 RPM.
Math is pretty simple. HP = Torque x RPM / 5252. Well known equation.

I'm not buying 425 ft lb at 2800 rpm either

 

[Digger556]

I have a warmed over 351W. It hits it peak torque ~425 lb-ft @ 3500 rpm and peak HP of 350 HP @ 5500 rpm.

Torque at 2800 rpm is only 300-325 lbft