'78 F150 9"

[Quasi242]

I am looking a buying a 1978 f150 9" to use on my 2000 Ranger prerunner build. After my research I am a bit confused about the dimensions. The '73-'90 F150 axles are reported to measure 58.75" housing flange to flange. The '78 F150 supposedly had a track width of 79.3". I have not found a flange to flange dimension for the 2000 Ranger 8.8, but I believe the width is is 58.25" wheel mount surface to wheel mount surface (Explorer 8.8 is 59.75" WMS to WMS and the Ranger 8.8 is 1.50" shorter than the Explorer axle).

I am running the Dixon Brothers long travel kit on the front of my Ranger. This kit extends the front track width by 4.5" per side or 9" overall. As such, to match the new front track width, my rear axle will need to be 58.25" + 9.00"=67.25" wheel mount surface to wheel mount surface. Allowing a 5" width allowance for the average difference between a housing flange to flange measurement and a axle flange to flange measurement, the 78' F150 9" axle should be roughly 63.75" wide axle flange to axle flange. If my math is correct, this would leave approximately 3.50" for the brake system hardware (I don't know how much width needs to be allowed for the brake setup).

My current front track width is approximately 78" from outside tire surface to outside tire surface. I am running 33X10.50 BFG Mud Terrains on 15" wheels with 4.5" back spacing.

I believe that the axles will need to be re-drilled to 5 on 4.5, and I will need to add an aftermarket ring gear to keep my ABS and other OBDII sensors running.

Based on this, I think that this axle will work for my application. Am I missing anything? Your help would be greatly appreciated. I don't want to buy and build an axle and then find that I missed something critical.

 

[4x4junkie]

F-150 axles are 65" WMS-WMS (some reports have it at 65.5").
Your Ranger axle should be 58.5".

If you need to keep your electronics going, the 8.8" may be the better axle to use. Stock for stock, it compares very similarly to a 9" in strength (the 9 has better aftermarket upgradeability though). The 8.8" also has a bit less internal friction, which can be helpful in getting more of a V6's power out to the tires.

However I have heard of some people rigging up sensors and tone wheels on their t-case (or transmission) outputs to mimic the sensor in the axle. Might be an option to look into if you're determined to use the 9.

Hope that helps.

 

[Quasi242]

Thank you for the response. I am torn between the Explorer 8.8 and the 9". The Explorer 8.8 would be the easier swap to get 31 spline axles, but the 9" will allow me to get closer to an even track width without using large wheel spacers. Additionally, the 9" does not suffer from a cast housing with plug welded axle tubes. This makes the 9" a better candidate to have an axle truss welded to it. Knowing the reported wms-wms dimension is very helpful, thank you.

On second thought, will an F150 8.8 match well with the Ranger electronics (plug and play)?

 

[1badexplorer]

Why not use a 8.8 from a fullsize F150 or Bronco then you will have a wide track width and the abs sensors

 

[4x4junkie]

Yeah, the F-150 8.8" was what I was referring to. Avoid '83-'86 8.8s though, these have the exceptionally weak factory carriers with ¾" crosspins (unless you plan on installing a full-carrier locking differential such as a Detroit Locker, then this won't matter).

Weld the tubes around where they go into the centersection. Spinning tube (plug-weld) problem solved

 

[crawlin91]

yep takes about a minute to weld those tubes in.

 

[Quasi242]

Since I am already looking at an F-150 axle, it seems that a 9.75 would not be out of the question. It would compare with a Dana 60 in terms of strength and would allow me to run a 34-spline axle. Do you know if the tone ring would be a direct plug and play? I know that the F-150 guys make this swap to replace their stock 8.8's. Additionally, does the 9.75 have the same axle to housing problems that the 8.8 suffers from? Thanks again for your help.

 

[85_Ranger4x4]

The 9.75 axle tubes are plug welded too. I would think the tone ring would be the same as the F-150 8.8 as well. The actual center case is a lot wider than the 8.8 which I think would help give it more strength.

99+ F-150 8.8's and 9.75's have disc brakes if you are into that.

Vans and Expeditions have 8.8/9.75 axles too.

 

[4x4junkie]

The 9.75" also has a metric wheel lug pattern (5x135mm IIRC). It is a good strong axle, although not near as much in the way of aftermarket support as even the 8.8" (not as many lockers, low gears, etc.).

 

[Quasi242]

Thanks for everyones help. I think that I am going to try the 9.75. I found a complete used posi/disk brake axle from a 2002 (67,000 K) F-150 for $400 on Craig's list. If the factory posi ever went out, I would probably run a Detroit Tru Trac which is currently available. Additionally, since I am 4X4 my front diff will restrict me to 4:88 gears (currenly supported on the 9.75). as 5:13's are not available for the IFS Dana 35 that I have in my 2000 Ranger.

 

[85_Ranger4x4]

Something else I just thought about, that style of F-150 uses the center hole of the hub to locate the wheels rather than conical lug nuts (they have a regular looking nut with a built in washer)

You might check that said hub isn't too big for the center hole of your wheel unless you are going to run adapters instead of redrilling them, with an adapter it probably wouldn't be an issue.

I don't know how big the center hole of my F-150 rims is offhand, but it is pretty good sized.

 

[Quasi242]

Good to know. I will need to look into that. I have not decided whether to redrill the axles or run the smallest spacer available that will allow me to adapt to my 5 on 4.5 wheel pattern.

Something else I just thought about, that style of F-150 uses the center hole of the hub to locate the wheels rather than conical lug nuts (they have a regular looking nut with a built in washer)

You might check that said hub isn't too big for the center hole of your wheel unless you are going to run adapters instead of redrilling them, with an adapter it probably wouldn't be an issue.

I don't know how big the center hole of my F-150 rims is offhand, but it is pretty good sized.