I have an 86 F-150 4x4 that I converted from auto to standard a while back. I still have some work to do. It has 4.11:1 rear end and I put in a 4-spd tranny with a granny 1st. See my problem yet?? No, well my tach is pegged at 3 grand at 65mph and the gas mileage ain't so great. I am having a hard time deciding what to do and would like some input/advise on the subject. I want to either switch out the ring and pinion gears or swap for a 5-spd tranny. I need to know if I can just swap the ring gears(been told certain gearing won't fit). Here's my specs and what I've figured out so far: T18 transmission, 9" rear end with 4.11:1 ring gear, don't know front gearing cause searches came up empty. Assume 4.11 as well. I don't do much towing and will mostly use the truck to haul and to get to camping spots. I also have aquired an 82 F-150 for parts with an 8" rear end and 3.55:1 ring gear. Can I use this ring gear in my 9"?? I've already been told to put a lift and bigger tires on it, but I'd rather keep it closer to the ground and I'm going for cheap and easy. I've spent enough time under this truck already. Let me know if I need to provide more info. Thanks

 

If the 82 is 4x4, then just swap both whole axles into your truck. You cannot swap the ring gear from the 8.8 into the 9 inch rear, but you should be able to swap the whole complete axle in place.

 

That's the problem. The 82 is only two wheel drive.
Can anyone clarify on this for me. I was told that if I switched to a higher gear that the ring gear would only fit one original axle (can't remember front or rear), and that I would have to replace the other axle. This just doesn't seem right to me but I don't know much about axles. Anyone else heard this or is it completely false??
Thanks for the help...

 

I have had much experience swapping ring-and-pinions, none of it good.

It is nearly impossible for a MECHANIC to set up a rear-end and it not have some ringing noise, or simply eat the teeth off in a couple years.

Rears set up in big factorys are lapped after assembly with machines and tools not available to the ordinary mechanic.


Sure, there are those who will say they can set one up in a flash with no problems, but a hard-driven tow-rig will soon make the short-comings of their work evident.



When possible, always buy an entire factory-set rear-end and swap the whole thing.

 

Front and rear gears ratios on a 4x4 don't have to match perfectly, but they do need to be very close to each other....say within .10. In the short term you can install a more common rear end gearing, like about 3.50, in the rear end, and not use the 4x4 until you get the front end swapped out.

 

I don't know who you've been dealing with, but that's just not true.

The 9" Ford is the easiest of all axles to setup, and anyone that knows what they are doing and has a dial indicator and some grease can set one up that will last a lifetime.

To the OP, you have a lot of choices. Either change both sets of gears, put two used axles in with 3.55's, or change your tranny over to a 5 speed (M5OD or ZF).

If you aren't hauling anything heavy or running really large tires, the M5OD will be fine and probably your cheapest (and easiest) swap.

 

been a few yrs since I drove my truck, since its all apart awaiting a trans rebuild, but seems to me my 86 f 150 4x4 with the aod trans runs at 2850rpm at 65 mph.... same gears as urs I think in the diffs and 31 inch tires.

Also, as I recall, the engine doesn't hit its peek power band untill 3000 rpm.But it averaged around 18 to 19 miles per gallon on the hiway

 

Juice, Maybe that's why you need the trans rebuild?? I had an AOD in mine before the swap and I am running 31's and I'm positive my engine wasn't running that fast at 65. At least not in OD. I'm not too concerned about the gas mileage. I am still getting about 15 MPG now. My main objective here is speed. I want to be able to better then 65 without having to worry about causing engine damage.

 

As I have already said, you have a couple of choices.

Change both sets of gears.
Swap the tranny to something with an OD.
Run bigger tires.

If it were me, I'd swap in either an M5OD or a ZF and keep the 4.10's. You'd have good pulling power and an OD for the highway.

What else are you looking for?

 

lol nooo.. trans has other issues.....but also been 4 yrs since i last drove it.. could very well be 1850 rpm...I honestly dont remember... guess must be 1850.. and power band starts at 2000 rpm.... I do remember it dies at 3800 and nothing after 4000 rpm... actually, the trans issue is either a plugged vent tube, or I suspect likely was from worn crank bearings.. found out only allowed 010 I think it is for the thrust bearings and when I tore the engine down, mains were worn quite bad..

 

Thanks for the help and ideas. I guess now I just have to make my decision and go from there. Again, Thanks for the advice.