needing help badly
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New User
Joined: Aug 2004
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needing help badly
I have a '77 F150 4x4 that I broke the rear axle on. Trying to find a new rear end for it and the tag that tells the gear ratio is missing. I have looked all over the rear end and can't find any numbers that all the "other" sites tell me should be there to get that info off of. the only numbers I have found are on the differential nest to where the drive shaft connects and they are the number "30" on the right side and what looks like "2k5" or possibly "zks" Not sure where to go next. sure could use any advise other than telling me to get rid of the truck. Too much love and blood between us... Any help????
Senior User
Joined: Oct 2003
Posts: 480
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From: Elyria, Ohio
Not sure about 1977; but just pulled chunk on my 9 inch in a 1979 F100. On the outside edge of the ring; it was engraved with 44 and 16 for number of teeth; forget context, but divide 44 by 16 = 2.75 which was my gear ratio that was also on the tag on the differential. This all agreed with the door tag code of 06, if I remember correctly. So you may not have to count teeth, which can make you dizzy after awhile.
Junior User
Joined: Mar 2004
Posts: 51
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How about just swapping the axle? Alot of times with mine, the splines will just strip out, then all you gotta do is count the splines and it should either be a 28 or 31 (?) spline axle, unless youre sure you broke something in the hoghead.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
A 4x4 should be a 31 spline. Just make sure to get one from the same side. They are to different lengths. Most common 4x4 gear was 3.50, but like mentioned above, see what the front axle says or try looking at the door tag if they haven't been changed.
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Laughing Gas
Joined: Aug 2004
Posts: 1,249
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From: Rockport, WA
Uh, not claiming to be a Ford expert here, but in general it's not always true that front and rear differentials are identical. Quite often, the front diff is a tiny bit "faster." Say a 4.10 in front and a 4.11 in the rear, for example.
Some can be quite different. My ex-Navy International 1300 has a Dana 70F in front that is 4.88 -- while the rear is a massive Timken (a truck design Engineer told me 10,000 lb. is the smallest Timken in that class) that I can tell by observation is in the neighborhood of 5 to 1. Someday I'll take it apart and know for sure, but in the meantime I've been warned not to lock it in 4WD on hard surfaces.
I would not count on front and rear differentials being an exact match, though it is quite possible and they will never be very far apart.
Good luck counting teeth.
Lane
Some can be quite different. My ex-Navy International 1300 has a Dana 70F in front that is 4.88 -- while the rear is a massive Timken (a truck design Engineer told me 10,000 lb. is the smallest Timken in that class) that I can tell by observation is in the neighborhood of 5 to 1. Someday I'll take it apart and know for sure, but in the meantime I've been warned not to lock it in 4WD on hard surfaces.
I would not count on front and rear differentials being an exact match, though it is quite possible and they will never be very far apart.
Good luck counting teeth.
Lane
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Posting Guru
Joined: Dec 2003
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From: Wichita, KS
I've seen what Lane mentions too--front end might a little bit higher-geared. Think the idea is that if you're running 4wd, you want the front end to lead the truck, rather than the rear end pushing it.
Logistics Pro
Joined: May 2003
Posts: 4,238
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From: Northern Illinois
Lane I am no expert either but on your typical 1/2 ton FORD the front and rear are going to be the same or like you said 4.10 or 4.11. It won't have 3.42's in the back and 4.10's in the front. They are not going to be as far apart as your old navy-International was, you must of had a lot smaller tire's on the front of that truck?
LXMan, different length axle's on the rear? Hmm
ydoc, if it is just a broken axle you will not have to replace the whole rear end.
LXMan, different length axle's on the rear? Hmm
ydoc, if it is just a broken axle you will not have to replace the whole rear end.
Laughing Gas
Joined: Aug 2004
Posts: 1,249
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From: Rockport, WA
I agree. And I don't know that the ratios are really far apart in my International. I can tell at a glance the the axles -- size, manufacturer, etc. -- are quite different, but I've never done more than count driveline revolutions with a wheel off the ground, to estimate ratio on the rear. I found the tag on the front.
No, I wouldn't expect them to be widely different -- though I did have a slightly goofy friend who put a 4.88 on one end of his Scout that had had 4.27 gears in both ends before he broke an axle. They gotta be CLOSE. And I'll take your word that half ton Fords will likely match.
These days, with an older truck, I think an entire junkyard axle will cost less than a professional differential rebuild.
Good luck.
No, I wouldn't expect them to be widely different -- though I did have a slightly goofy friend who put a 4.88 on one end of his Scout that had had 4.27 gears in both ends before he broke an axle. They gotta be CLOSE. And I'll take your word that half ton Fords will likely match.
These days, with an older truck, I think an entire junkyard axle will cost less than a professional differential rebuild.
Good luck.
