Gear ratio recommendation

[msmith]

A couple of years ago I completely rebuilt the front axle. New Seals, bearings, races, axles, etc. and regeared from 3.50 to 4.10 while at it. Shortly thereafter, while working on it, it somehow came apart piece by piece and is now spread across my garage. Now that winter has set in, I am in the process of reassembling the chassis and my focus right now is the rear end. I'm going with all new except the housing and third member housing. New 31 spline axles, Truetrac, and of course, new gears.

So my question is, since I already have 4.10 in the front, should I regear to 4.11 in the rear, or go ahead and swap both out for 4.56? I kinda dread breaking down the front again and swapping gears but it is what it is.

Right now I have a 2.5 inch suspension lift and a 2 inch body lift. The plan is a mildly built 302 or possibly a rather stock 351 if I can find a decent take off, and an AX15 transmission. Probably going uncut with 33s. I MIGHT stick with the original RAT transmission just to expedite things but am thinking that I should just go ahead and do the conversion while the body is off.

Calculator shows that with 4.11, 33s, and an AX15, engine rpms would be between 2300 & 2350 at 70 mph. Is this going to be enough to push a Bronco down the road without issues?

Thanks,

Mike

PS, obviously I never engaged the front axle.

 

[Broncobowsher]

I think you should be OK with that. If anything I would lean toward the 351 to balance things out. Displacment and compression are torque. 'Built' engine tend to shift the powerband up.

 

[JB Fab]

One of the wife's Broncos is a 351W (built for low-end torque), AX15, 4.10, W/35" tires. I think it is a great combo, but the gearing could be just a little bit lower (33" tires would correct that), I agree with Broncobowsher "Displacement and compression are torque. 'Built' engine tend to shift the powerband up."

​

 

[chuck1022]

One of the wife's Broncos is a 351W (built for low-end torque), AX15, 4.10, W/35" tires. I think it is a great combo, but the gearing could be just a little bit lower (33" tires would correct that), I agree with Broncobowsher "Displacement and compression are torque. 'Built' engine tend to shift the powerband up."

​

How many broncos does your wife have?

 

[JB Fab]

Four....

67
68
74
24

 

[fordguy]

A couple of years ago I completely rebuilt the front axle. New Seals, bearings, races, axles, etc. and regeared from 3.50 to 4.10 while at it. Shortly thereafter, while working on it, it somehow came apart piece by piece and is now spread across my garage. Now that winter has set in, I am in the process of reassembling the chassis and my focus right now is the rear end. I'm going with all new except the housing and third member housing. New 31 spline axles, Truetrac, and of course, new gears.

So my question is, since I already have 4.10 in the front, should I regear to 4.11 in the rear, or go ahead and swap both out for 4.56? I kinda dread breaking down the front again and swapping gears but it is what it is.

Right now I have a 2.5 inch suspension lift and a 2 inch body lift. The plan is a mildly built 302 or possibly a rather stock 351 if I can find a decent take off, and an AX15 transmission. Probably going uncut with 33s. I MIGHT stick with the original RAT transmission just to expedite things but am thinking that I should just go ahead and do the conversion while the body is off.

Calculator shows that with 4.11, 33s, and an AX15, engine rpms would be between 2300 & 2350 at 70 mph. Is this going to be enough to push a Bronco down the road without issues?

Thanks,

Mike

PS, obviously I never engaged the front axle.

Swap rear end first, easier and cheaper. Bonus, you get to see how the 4.56s do. My current situation, used 4.11 chunk in rear with an all rebuilt 4.11 Dana. I have a tru trac 9 inch and new 4.56s, going to build that and run it, if I like it I will then change out Dana. I decided way to early on 4.11s and had the front end built.

 

[Shimmy]

i have 4.56s, truetrac, 3 spd, 302, and 35s. i really like it. if you're sticking with 33s and going with an ax15, id think 410s would be very pleasant for street driving.

 

[msmith]

Swap rear end first, easier and cheaper. Bonus, you get to see how the 4.56s do. My current situation, used 4.11 chunk in rear with an all rebuilt 4.11 Dana. I have a tru trac 9 inch and new 4.56s, going to build that and run it, if I like it I will then change out Dana. I decided way to early on 4.11s and had the front end built.

I get it. That's where I'm at.

 

[gnpenning]

Anytime I see one of these threads I wonder what is the normal driving conditions. Flatland or hilly/mountain area? What are your normal driving conditions like?

Don't forget you have a in-between choice. 4:30

 

[Broncobowsher]

One of the wife's Broncos is a 351W (built for low-end torque), AX15, 4.10, W/35" tires. I think it is a great combo, but the gearing could be just a little bit lower (33" tires would correct that), I agree with Broncobowsher "Displacement and compression are torque. 'Built' engine tend to shift the powerband up."

​

There you go. The 4.10 option with 33s and the AX15 is a 351 for the win.

 

[Broncobowsher]

Anytime I see one of these threads I wonder what is the normal driving conditions. Flatland or hilly/mountain area? What are your normal driving conditions like?

Don't forget you have a in-between choice. 4:30

4.30 or 4.27
I believe the 4.27 is a Dana ratio. The 9" can gear nearly any conceivable ratio if you know the places to look.

 

[Soylent]

I would go with the 351. I have a blueprint 302 with 385hp, ax15, 2.5” lift, 4.10 and 33s. It doesn’t have that break-it-loose umph. If I was going to do it again I would have done the 351

 

[Broncobowsher]

I did a couple different small block builds many years ago. Milder 351 and a little more built 302 (that did get a small 3.25" stroker kit). Both put ~250 HP to the ground on the same chassis dyno. The 351 was way more fun to drive. The 302 was way more likely to get you criminal speeding ticket.

 

[msmith]

Anytime I see one of these threads I wonder what is the normal driving conditions. Flatland or hilly/mountain area? What are your normal driving conditions like?

Don't forget you have a in-between choice. 4:30

WV hills, 2 lane highways, backroads, occasional interstate. I should have mentioned that

 

[Apogee]

Before my most recent reincarnation, I was running a strong running 351W with the three speed trans, 33" tires and 3.50 gears, and it did just fine. To be honest, the 33's were probably more like 32's on a good day without taking tread wear into account, but it was a rocket ship that could break the tires (old BFG M/T's) loose on wet or dry pavement and did just fine at any speed going over the Cascades. I think 4.11's would have been the preferred gearing for that setup, but I agree with the comments about torque and displacement, as it was really fun to drive setup like that IMHO.

 

[Chiclassics]

Uncut with 33s you are okay with 4.11 as you already have 4.10 in front.

WV hills, 2 lane highways, backroads, occasional interstate. I should have mentioned that

so if your driving includes 2 lane highways and backroads more than interstate 4.11 would do job just fine.. If you go 4.56 your highway cruise RPMs might be higher than 2500, which again 302 doesnt mind but thats not ideal. All in all as folks mentioned 4.11s are just fine. Your 4.5 overall lift will allow 33s from a height perspective (3.5 min lift needed) however with uncut sometimes 33s might rub when you turn full steering. Unless you have some offset on wheels so test those first before deciding gearing options.

 

[msmith]

Y'all have me scrolling through marketplace looking for a 94-97 351

 

[nvrstuk]

You don't need a roller block 5.8. However, don't build a 351W w/o a roller cam and rockers beause you lose too much w/o installing a great induction system.

You can retrofit rollers into any 351W block. The problem with the roller blocks is quite frequent cracking from the valley to the #2 cam journal that usually shows in the oil galley "hole" in that cam brg bore. I've found this out from Jim and they are out there so IF you BUY a used 5.8 roller block from those years don't spend any coin till the cam brgs are pulled and you can inspect. I've built more than a few of these and my .02 is to go retrofit rollers in an earlier block.

Also, I know you're not interested but you don't move up the powerband for hp/tq (really) if you start out with double the torque #'s because you put a stroker motor in.

 

[gnpenning]

4.30 or 4.27
I believe the 4.27 is a Dana ratio. The 9" can gear nearly any conceivable ratio if you know the places to look.

correct Nice spot when thinking the 4:56 is to low and the 4:11 might be to high. @msmith

 

[ntsqd]

4.30 or 4.27
I believe the 4.27 is a Dana ratio. The 9" can gear nearly any conceivable ratio if you know the places to look.

I put 4.27's in the Wagon's 44s. 4.11 was too tall, and 4.56 was too deep to hit the rpm vs. mph of the stock donor application for the power-train. pushed, the 4.56's were closer and had the 4.27's not been available I'd have gone with the 4.56's.
Maybe not important, but worth noting is that there are no Dana 4.27's or 4.30's for a rear D60. Yukon is the only choice for that ratio.
Also worth noting is that the D60 carrier split is between 4.11 and 4.56 as far as I've found so far (which has not yet been very in depth) Yukon doesn't say which case their 4.30's are intended to work with. I don't recall where it is for the D44, but that could affect the choice.