I have an 84 f250, and the rear end that's in it is all locked up. It has 354 gears and the tag on the front matches it. My buddy told me it would be no problem putting the 353 rear end I have laying around under it, it is out of an early 80s 250 van. Any advise on this would be greatly appreciated. Thanks

 

You will have to fab up new spring perches as the van and truck frames aren't at the same location.

And I see no problem with that gearing, as long as you don't use 4wd on dry pavement...

Because usually on 4x4's the front pig is always 0.01 taller.


For example, my 1990 F250 has 4.10's in the back, witch means the front is 4.09

My 1994 F150 has 3.08's in the back, and that makes the front have 3.07.


I'm not 100% sure why is this, but this is what i've been told. but a .01 difference won't hurt anything.

 

Thank you for your time. That's what I thought but it threw me off that both the tags said the same thing. But thanks again for taking the time to let me know! Oh and yea I thought the frame rails were different widths, but moving the perches should be relatively easy as opposed to rebuilding the rear end

 

Have you looked up any actual trucks to verify this? First time I have heard of this "rule". My 89 has a 4.10 front and a 4.10 rear. My 80 had a 3.50 front and a 3.50 rear. I agree if they are close they will work, but have never heard of a factory "rule" about them being slightly different.

 

As far as I know, there is no set rule about the front being .01 different than the rear. My truck has the 3.08/3.07 gearing in it and from what I understood, they're geared .01 taller so that the front pulls more. It's such a little difference though, that it's negligible in reference to drive-line bind.

Personally, I feel that the .01 difference doesn't matter at all. I'd just as soon have them matching as I would have them 3.08/3.07. Either way, unless you've got a limited slip or a locker in the rear or the front, in 4x4 it's still a "two wheel drive" when you've got two open differentials.

The OP needs to find a 3.55 rear.

 

3.54 or 3.55, close enough.
the reason for the 0.01 difference is that the front tires cover more ground as you go around corners, and that small difference helps compensate for that.
if you work over the 3.53 to fit, i would suggest running newer tires on the front than on the rear, as the difference in treadwear would have the same effect as the proper gearing.
on a truck i used to have, i had 3.07 front and 3.00 rear with 31" rubber rear and 32" front. it worked just fine because the tire difference perfectly compensated for the gear difference. i won't get into the whole story behind it.

 

Here's the front gears that were available in 1985 for a f150
3.07 ratio
3.54 ratio
3.50 ratio
4.09 ratio

Here's the rear for the same;
non-removable carrier (8.8" RG), 2.47 ratio
non-removable carrier (8.8" RG), 2.73 ratio
non-removable carrier (8.8" RG), 3.08 ratio
non-removable carrier (8.8" RG), 3.55 ratio
non-removable carrier (8.8" RG), 4.10 ratio
removable carrier (9" RG), 2.47 ratio
removable carrier (9" RG), 2.75 ratio
removable carrier (9" RG), 3.00 ratio
removable carrier (9" RG), 3.25 ratio
removable carrier (9" RG), 3.50 ratio
removable carrier (9" RG), 4.11 ratio

I am not sure about this, but I believe the little differences you are seeing are from the different axle designs and what they had available for them.

I would venture to guess if you had a 3.07 front, your truck would not have come with a 9 inch rear, but instead come with the 8.8 3.08 ratio. If your truck came with a 3.50 frontend, it would probably had to have the Ford 3.50 9 inch rear, but if you had the 3.54 frontend, you would have had the 8.8 3.55 rear.

 

In 1980, the 8.8 was not available yet. The only two ratios offered in the front for a f150 were;
3.00 ratio
3.50 ratio

The rear was always a 9 inch, and here are the ratios for 1980;
(removable carrier, 9" RG), 2.47 ratio
(removable carrier, 9" RG), 2.75 ratio
(removable carrier, 9" RG), 3.00 ratio
(removable carrier, 9" RG), 3.25 ratio
(removable carrier, 9" RG), 3.50 ratio
(removable carrier, 9" RG), 4.11 ratio

Notice they offered a 3.00 frontend to match the 3.00 9 inch rear. But this combo must not have been offered in the later trucks like in the previous post.

 

Franklin, you're right. The 3.00 ratio was only offered in '80 and '81. The reason I am having such a hard time finding them.

 

I got a few hits in Wisconsin on the 3.00 axle.

1980
Front Axle Assy.
Ford Truck 150 3.00, FRONT CARRIER ONLY 0 AFT NOF $175 McDill Auto Wrecking, Inc. RP+ Member USA-WI(Stevens-Point) Request_Quote 1-800-332-4491 Request_Insurance_Quote
1980
Front Axle Assy.
Ford Bronco 121,347 A 980098 $175 McDill Auto Wrecking, Inc. RP+ Member USA-WI(Stevens-Point) Request_Quote 1-800-332-4491 Request_Insurance_Quote
1980
Front Axle Assy.
Ford Bronco 4X4 FRONT, 3.00 0 AFT NOF $175 McDill Auto Wrecking, Inc. RP+ Member USA-WI(Stevens-Point) Request_Quote 1-800-332-4491 Request_Insurance_Quote
1981
Front Axle Assy.
Ford Truck F150 3.00 ratio-100+ COMPLETE-100+ 174,000 A 051213 $150 K.A.M. Auto Salvage USA-WI(Arkdale) Request_Quote 1-866-564-2244 / 1-608-564-2244 Request_Insurance_Quote

 

McDill Auto? Why didn't I think of them. I know a guy that works there, and they are only 30 minutes away. Boy do I feel stupid now.

Thanks for the info.