another ideal gearing question... (big block/35s)

[76 explorer]

its not a eb question but its still a bronco (78 bronco)

the specs of this thing are 460/c6/205 t/c

my question is with this set up what do you think the ideal gearing would be to run 35 or 36 inch tires since it has a healthy big block in it? it will see highway driving and some occasional wheeling. but it only has 2.8x gears in it now so i am sure i will have to regear it just not sure which gears heh

 

[wildbill]

;D ;D ;D It should have lower gears so the motor can run in its power band. If you run them to low they will burn valves. Or you can do like the big gas trucks and go to a sodium valve very expensive but wont burn. Good luck. Bill ;D %)

 

[mtkawboy]

Beware of sodium valves if you turn it hard. Medium riser 427's had a bad habit of swallowing them, guess how I know. The valves might be better now though

 

[76 explorer]

i thought the power band on a big block was in the lower rpm range so wouldnt that mean a higher gear (lower number)than say a small block? like say 4.11 for 35s? instead of 4.56 for say a small block and 35s.

 

[cro_bronco]

With aa big block and 35's I suggest 3.50 or 3.73s, and I wouldn't go any lower the 4.11s. I run 4.11s with my small block and on the highway running 65 to 70 it is turning 2800 to 3000 rpms. With the added power of a big block I would run a higher gear. The 3.50s should be real easy to find.

 

[mag409]

79 f-150 460 c6 with 4.56's and 35's. RPM's are in the 2800 range at cruising speed. We built the truck to run 38's-40's but got a good deal on the 35's for the time being. If you planned on mostly highway driving I would go with 4.11's at the most.

 

[fatcatmatt74]

a couple things. i run a 79 bronc 460/c6/205 with 18/39 boggers on a 10 in wheel. it turns about 2500 at 55mph with a 4.88 gear. its a good compromise for street/woods and really wakes up that 460. that said pick your tire and match your gears. and remember that seldom does a advertised size match an actual size the last set of swampers i bought were 15/35/15 on the reccomended 15x10 rim they were just over 34 in tall at reccomended inflation. swampers have a good reputation for being close but I have rarely seen any 35x12.50 radial measure over 34 inches tall. so mount them up THEn measure them..

 

[Mr Joe]

Mostly street I'd run 3.73's... With trail/offroad use I'd go 4.11's. If you plan on going bigger than 35's, I'd look at 4.56's

 

[broncnaz]

Are you sure about the gears in it now I've never seen 2.8 gears in any 78/79 bronco or f150/250 4x4's they usually had 3.50's you should be ok with 3.50's but 3.73s or 3.90's would be better you may want to swap a camshaft in that matches your RPM range. A few years back I built a 460 that was in an F250 used a Edlebrock performer cam and intake swapped in a 3.73 D60 with stock tires that thing would burn the tires off and got 12 MPG pulling a 26 foot trailer.

 

[nvrstuk]

gears

Compromise is where you're at. For optimum mpg and still maintain some power at 65-70 mph you're looking at 1800 rpm. Problem is how slow do you want to go off road? With only a 205 for 2:1 gearing off road that's marginal at best...I don't care if you have an auto, that's not very slow. If your aren't into slow going or rocks you should be OK if you watch the tranny temp.

How about keep the same diff gear ratios (2.8 sounds very high) and solving your off road problems with a gear doubler for off roading. You would still have great highway manners and great control off road. Best of both worlds!

 

[76 explorer]

yeah guys im absdolutely sure i have 2.8 gears. 1st one ive ever stumbled across like this but i do have all the paperwork fromt he original owner that shows he special ordered it with 2.8 gears. plus the tag on teh diff shows them as 2.8 as well. ?:?


anyway so you guys think a 3:73 gearing with 35 or 36 should do me well? the big bronco is going to be mainly a daily driver but a weekend wheeler as well for those rainy/icy days. as it is now with 31's and the 2.8's its like pulling teeth to keep it under 75 mph. it just wants to keep pulling ;D but id like to be able to run the same size tires on my 76 and my 78 so.... i wont be going any larger than a 36 for this bronco. thanks for the ideas guys