Differential Swap

dadstruck · Post by **dadstruck** » October 5, 2008, 7:18 am

Has any one tryed fitting a 97 Ford Explore differential into a 60 to 64 F100?
The reason for asking is my 64 F100 with it's 91 302V and auto tranny are giving poor gas milage, with the original 4:10 posi rear end. The 91 truck had a set of 3:55 in it, but the axle assembly is too wide to fit into the 64.
I have found a 97 Ford Explorer an 8.8" diff, with disc brakes and a posi. The axle assembly is a little narrower than the 64 but it will require stud adapters to get from the Explore bolt pattern to the F series pattern bringing the assembly to the correct length. Yes I will need to move the spring and shock mounts, emergency brake cable, these are minor issues.

Yes can get a set of 3:55 gears for the original differential but I will need to get a new carrier also $$$$$$ $1000.00 Plus. If I can find a posi.

Pros for doing it.
Better fuel milage, Disc brake, posi. rear end, easier to find and get different gear sets

Con for doing it
A lot of work, 600 lbs. less load carrying capacity

Thoughts.

fmartin_gila · Post by **fmartin_gila** » October 5, 2008, 9:09 am

I personally am not very fond of wheel adapters. They do have a tendency to have the lugs work loose, but locktite may help that situation. Would it be possible to redrill the brake hats? The 3.55 will not be that much of an improvement over the 4.10 considering the cost involved. What about a 3.08?

Hawkrod · Post by **Hawkrod** » October 5, 2008, 9:21 am

dadstruck wrote:Has any one tryed fitting a 97 Ford Explore differential into a 60 to 64 F100?
The reason for asking is my 64 F100 with it's 91 302V and auto tranny are giving poor gas milage, with the original 4:10 posi rear end. The 91 truck had a set of 3:55 in it, but the axle assembly is too wide to fit into the 64.
I have found a 97 Ford Explorer an 8.8" diff, with disc brakes and a posi. The axle assembly is a little narrower than the 64 but it will require stud adapters to get from the Explore bolt pattern to the F series pattern bringing the assembly to the correct length. Yes I will need to move the spring and shock mounts, emergency brake cable, these are minor issues.

Yes can get a set of 3:55 gears for the original differential but I will need to get a new carrier also $$$$$$ $1000.00 Plus. If I can find a posi.

Pros for doing it.
Better fuel milage, Disc brake, posi. rear end, easier to find and get different gear sets

Con for doing it
A lot of work, 600 lbs. less load carrying capacity

Thoughts.

I have to stop and correct you here. You have an F100 and so if you don't have a 9 inch rear (maybe you have an optional Dana limited slip rear) then swapping in a 9 inch is really the easy and cheap way to go. The 9 inch has more ratios available than just about any rear and it is cheap and easy to pick up a 3.50 at teh local auto wreckers just about anywhere. Disc brakes and limited slip are also both options for a 9 inch. The disc brake conversion is pricey but not too bad and used centers are everywhere on eBay. To put an Explorer rear in will require mods and then spacers/adapters (wheel bolt pattern is different). Unless you have to have rear disc brakes just because you have to the 68-72 ar more brakes than your 64 F100 needs in the back. If it was mine (and I did a 61 last year and did this) I would go to the local wreckers and find a 68-72 with a 9 3.8 rear, pull the center section out and then find a 80-86 with a 31 spline 3.50 Trac Lock and use that center and bolt it back together and then haul it up to the cashier. Mine cost $65 on half price day. Took it home cleaned it all and put new seals and brakes in it and we were ready to roll for $150 and 3 days hard labor (but isn't that what we do? and besides it will take more than three days to fit the Explorer rear!). Hawkrod

DCarr · Post by **DCarr** » October 5, 2008, 1:14 pm

Just remember that later Ford truck rear axles are offset to the right side (passenger side). 61 to 64 trucks would need to have the engine & trans offset to keep the driveshaft parallel . I agree, the Ford 9in. is the way to go.

dadstruck · Post by **dadstruck** » October 5, 2008, 3:34 pm

The rear end that is in the truck is a Dana 40 or 44 ?
Most of the wreckers in my neighborhood crush anything over 15 years old.
I agree, I am not enthused but using wheel adapters.
Any suggestions as to what rear axle assemblies will fit.

Hawkrod · Post by **Hawkrod** » October 5, 2008, 3:42 pm

DCarr wrote:Just remember that later Ford truck rear axles are offset to the right side (passenger side). 61 to 64 trucks would need to have the engine & trans offset to keep the driveshaft parallel . I agree, the Ford 9in. is the way to go.

You do not need to offset the engine just because the pinion moves. All you have to do is make sure the pinion angle is correct side to side (most people are used to only doing up and down but with swaps, side to side must be done as well. Hawkrod

DCarr · Post by **DCarr** » October 5, 2008, 7:15 pm

If that is correct , then why did Ford offset the engines & transmissions in those same trucks ? I'm under the impression that you want to limit the number of different angles on the driveshaft- pinion angle matched to engine angle and driveshaft parallel to the crankshaft & pinion centerline. It may function when its not parallel to the centerline but when you look under the truck it looks like someone with limited skills (or intelligence) built it . The correct way to build engine & transmission mounts for a swap is to use plumbobs from the front of the crankshaft centrline, the rear transmission centerline and the front of the pinion centerline. then you have to make sure they line up for proper operation. Now if you misunderstood what I originally said maybe this cleared it up for you. I have personal experience with this particular axle swap- my 64 has one and I assure you that my engine and transmission centerline was moved to the passenger side an equal amount of the offset.

Hawkrod · Post by **Hawkrod** » October 5, 2008, 8:02 pm

DCarr wrote:If that is correct , then why did Ford offset the engines & transmissions in those same trucks ? I'm under the impression that you want to limit the number of different angles on the driveshaft- pinion angle matched to engine angle and driveshaft parallel to the crankshaft & pinion centerline. It may function when its not parallel to the centerline but when you look under the truck it looks like someone with limited skills (or intelligence) built it . The correct way to build engine & transmission mounts for a swap is to use plumbobs from the front of the crankshaft centrline, the rear transmission centerline and the front of the pinion centerline. then you have to make sure they line up for proper operation. Now if you misunderstood what I originally said maybe this cleared it up for you. I have personal experience with this particular axle swap- my 64 has one and I assure you that my engine and transmission centerline was moved to the passenger side an equal amount of the offset.

Nope, no misunderstanding at all. In fact, if you look at different Ford engines in the same chassis some are offset more than others, not all are the same centerline that you are seeking the way you do it. Ford offset the engines to allow them to fit not because they needed to. Moving the engine to the right allows more clearance for the steering and clutch linkage but some engines are much more centered than others as clearance was not an issue with those engines. Ford's only concern was that the angles are correct not that the centerline is straight. It makes no difference how many angles you have as long as the angles are accounted for properly. As a side note, All 1957-1967 F100's with a 9 inch have the same rear centerline and use the same axles. Ford trucks are unusual as they use the same size axle left and right and F100's with 9 inch rears use two B7TZ-6234-A axles so the issue is actually irrelevent. Also note that 68-72 also has the same centerline but when they widened the brakes they widened the axles also. The 68-72 rears are about 3/4 inch or so wider than the earlier ones but interchange just fine. Hawkrod

Rosati · Post by **Rosati** » October 5, 2008, 8:26 pm

DCarr wrote:If that is correct , then why did Ford offset the engines & transmissions in those same trucks ? I'm under the impression that you want to limit the number of different angles on the driveshaft- pinion angle matched to engine angle and driveshaft parallel to the crankshaft & pinion centerline. It may function when its not parallel to the centerline but when you look under the truck it looks like someone with limited skills (or intelligence) built it . The correct way to build engine & transmission mounts for a swap is to use plumbobs from the front of the crankshaft centrline, the rear transmission centerline and the front of the pinion centerline. then you have to make sure they line up for proper operation. Now if you misunderstood what I originally said maybe this cleared it up for you. I have personal experience with this particular axle swap- my 64 has one and I assure you that my engine and transmission centerline was moved to the passenger side an equal amount of the offset.

Your wrong.
As long as the centerline of the pinion is parallel (vertical and horizontal) to the centerline of the transmission output shaft and within the degree range of the u-joints, the driveshaft can look "like someone with limited skills (or intelligence) built it"

I suggest you read this website as it will give you a better understanding.
http://www.4crawler.com/4x4/CheapTricks ... -101.shtml

I have centered the engine in my F100 and had a 1pc driveshaft made. It put the driveshaft at an angle when viewed frome the front of the truck looked odd.

DCarr · Post by **DCarr** » October 5, 2008, 9:28 pm

Thanks for the info. I agree that it will work and that factories will compromise for fit. However that does not mean it is correct. All the street rods, drag cars, road racers, and others I've been associated with in 38 years have been built with the centerlines done as previously stated. So let's agree to disagree and next time I'm up your direction I'll buy you a brew and we can continue the debate. Later, David

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » October 5, 2008, 9:38 pm

my mercury has a 95 F-150 rear under it

dadstruck · Post by **dadstruck** » October 5, 2008, 10:46 pm

Junkyard Dog

How is the clearance between the wheel wells and the tires. My 91 F150 is four inches longer than the 64 axle assembly. Is your truck the flare side in the picture, I have a styleside.

Hawkrod · Post by **Hawkrod** » October 5, 2008, 10:46 pm

DCarr wrote:Thanks for the info. I agree that it will work and that factories will compromise for fit. However that does not mean it is correct. All the street rods, drag cars, road racers, and others I've been associated with in 38 years have been built with the centerlines done as previously stated. So let's agree to disagree and next time I'm up your direction I'll buy you a brew and we can continue the debate. Later, David

You are welcome to disagree but from a technical standpoint you are mistaken. In fact, the only reason it is done as you suggest is for aesthetics. The reality is if you try and make it perfectly straight it will destroy U joints. There has to be angles on the shaft and as long as they are not too severe it does not matter what angle but the steeper the better. This may seem counterintuitive but you need the angles to force the trunnion bearings to move otherwise they will dig in and destroy the bearing surface. I have had to fix a ton of street rods over the years because so many builders don't understand this and end up with chronic vibrations and bearing failures. If it makes you feel any better, I will swear that 3/4 of my engineering class didn't get the concept originally either! Hawkrod

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » October 6, 2008, 5:29 am

dadstruck here is pic of my rear yes its a stepside and wheels come out almost even to the fenders,, also I have put the Mark V Rear dics under these trucks but are different bolt patterns with about the same distance

http://i512.photobucket.com/albums/t325 ... 0_3408.jpg

Johnny Canuck · Post by **Johnny Canuck** » October 6, 2008, 8:32 am

These trucks have lots of "meat" to the fenders, the longer rear ends off the later models work just fine if you aren't trying to fit your huge offset aftermarket wheels back under the fenders. I have a '79 4x4 rear end under mine and still have about an inch and a half to 2" to the fenders. The Merc wheels are negative offset tho.
[albumimg]61[/albumimg]

DCarr · Post by **DCarr** » October 6, 2008, 11:37 am

Agree that there has to be some angle on the shaft for the u- joints to live. I guess I'm just old school and it has to look right front to back. Whenever I see a shaft angled from side to side I think farm equipment instead of streetrod. Thanks , David. Are there still a lot of vintage aircraft up at the airport ? I,d like to take another look at them sometime.

dadstruck · Post by **dadstruck** » October 6, 2008, 10:41 pm

Thanks guys I will have a closer look at fitting the 91 rear end. At first glance it looks as if I only have about 3/4" clearance between the wheels and the fender. I'll also take the locking diff. from the 97 Explore and fit it into the 91 F150 housing.

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » October 7, 2008, 6:14 am

if this is any help, I bought a new differential cover for mine from Ford and the coverage was wild fit from 1980 to 96 on F-150's , expeditions, explorors

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » October 7, 2008, 7:59 pm

dadstruck I took these 2 pics one on each side to show the clearance and these are 15x8 Ford Truck Steel Wheels with stock springs and no overload or air shocks just to give a :?:

shockshttp://i512.photobucket.com/album ... 0_3409.jpg

http://i512.photobucket.com/albums/t325 ... 0_3410.jpg

6166 Junkyard Dog · Post by **6166 Junkyard Dog** » October 7, 2008, 8:01 pm

lets try this again, 1st pic did not come out

http://i512.photobucket.com/albums/t325 ... 0_3409.jpg

Differential Swap

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