i am sitting at almost 3000 rpm at 65 mph. as far as i know the suspension is all stock ring gear should be stock and it has 32" tires on it. (84 bronc, 351w, c=6 auto, np-208, 9" rear) what do i do? different ring gear? how do i know which way to go higher or lower gear?

 

First you need to find out what your stock gears are.......then do some math with tire size/RPM.....then re gear.

The thing is that with a C-6 there is no OD.....so if you gear it for the highway, you will have to give up some low end.

Search this forum a bit and you will find PLENTY of info on how to find your gear ratio, and what to do to "get it where you want it".

 

ok, i spend most of my time on the highway and with gas prices constantly on the rise i dont mind giving up a little low end for better highway milage. where do i start looking in here to find that formula? thanks streetgang.

 

Yo.....I cant search it out for you right now........use the "search function" for this forum. There was a post like two days ago talking about gearing and even posted a chart.

I dont know for sure, but in my truck I have 3.55 in the rear (I run at about 1900RPM @ 70MPH with 31x10.5"s).....if I wanted to lower the RPM on the highway, the number would have to go down.....like 3.20.
Just remember though.....in order for you not to F up the drive line you also have to regear the front dif also.

 

thanks very much. i didnt want you to find it for me i just wondered if there was a certain forum to check but you answered that for me.

 

Just look back a few days.....

 

Your Bronco should have 3.55 gears, if stock, there is something wrong, because those rpms are to high, that can't just be the gears. I run about 2500 at 70mph(3.55 gears and 28" tires, so if I'd have 31" tires my rpms would be lower.) you run 32s so yours should be closer to 2000 with those gears.

 

but his is a c6. with an OD tranny then yes his rpms would be lower. Skeletor you would be best to look into some larger tires to offset the hwy rpms. running a 33+ would be best. most stock gears for 9" were 3.50's but it could also have factory 4.10's as well. look on your door jam at axle code and post back here . also look on the diff tag

 

Why SHOULD it have 3.55's?

 

Well I don't know for sure, but bronco's came with those unless they got the put graded gearing from the factory. That's assuming everything is factory. Now if you did have the 4.10 gears, then your rpms would be lower, because they wouldn't be spinning as fast as the lower # gears, such as 3.07 or so. But those gears won't improve your gas milage, beacuse it will take more power to get them stated in low gears(transmition) using more gas.

If you don't understand, I'll try to explain better,
-Matt

 

stock 3.50 was 9" when they went to 8.8 rear they had 3.55.

 

I found out that my uncle had 4.10 gears swapped into the 9" but not the front d44 ifs job. Now I understand that you need to have the same gears front and back? What is the reason for that? also if i put a 2" body lift on would i have room for 33" or 35" tires? Or do i need a suspension lift for that? Putting on the larger tires would help my rpm problem right? Thanks for all your help guys.

 

If you put a 2" body lift and trim, your finders, you could fit 35s, which would help with the RPMs alot. 35" tires and your 4.10 gears are a good combination. You could get a cheap 4" suspension lift($300-400 and install yourself), and then you wouldn't have to worry about lengthening anything like with a body lift, and you wouldn't have to trim you fenders.

Those different gears are BAD! Your uncle shouldn't have done any gear work if he wasn't going to do the front to. You should look into regearing the front too($550 or so parts and labor).

 

You need to re gear both the front and rear at the same time, because there is no viscus coupling or clutch that would allow slippage in the t-case. It is all locked together, so if the front is turning slower/faster than the rear.....smoething WILL HAVE TO GIVE, and replacing drive line parts ain't cheap. You understand yet????

 

ok, i didnt know that both the front and rear drive shafts spin at the same speed when in 4wheel drive. thanks streetgang