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Changing Rear Ends?

I have two Ford pickups. One is an '89 F-250 Lariat 4X4, auto with a new 460 engine. The other truck is a '90 F-150 Lariat 4X4 auto w/OD, and a well worn

302. Both are now "work" trucks and are driven every day.

The F-150 still runs well, even with all the miles on it, and it gets EXCELLENT, (or, at least, I'm satisfied with it) gas mileage. Unfortunately, the F-250 doesn't.

I didn't realize it when I purchased it last fall, but, I think it must have been a specially ordered pick up because it has an extremely low-geared rear end, and NO overdrive.

At 55, you can hear that big 460 whine, like it's stuck in a lower gear, but, according to several reliable mechanics, it isn't. The truck was obviously built to work off-road more than on. Hence, the low gearing.

My 1st question is, does anybody know if I can get a higher geared rear end for it? The second, will I have to change the ratio in the front axle as well? Won't that affect it's 4-WD capabilities if I don't? Thanks in advance!

Joe

Reply to
Joe Hartley
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snipped-for-privacy@webtv.net (Joe Hartley) started a controversy when he said in news: snipped-for-privacy@storefull-2175.public.lawson.webtv.net:

Yes, the ring and pinion can be change to a numerically lower gear(lower ratio). By the way you describe it, I would guess the current gear to be around 4.10:1 and with that motor you probably don't need anything higher than a 3.55:1. Then again, I suppose you could just install a set of monster truck tires, that will effect your final drive ratio too.

Yes, you will have to match the ratios in both axles.

Reply to
Robotron Tom

I've changed rear ends four times. I like this last one, I think I'll keep her :)

Sorry, just had to.

Reply to
Indianaradio

I actually had a 4 wheel drive truck with different geared axles. It had a

3.92 Dana 44 front and a 9-inch Ford rear. Now, they don't make a 3.92 9-inch Ford, they make a 3.90. So that was considered "close enough" when it was built. When I got it, the rear was a 3.70. Somebody had changed it. The problem gets worse by degrees as the speeds differ more.

Anyway, if you have this situation the wheels are going to turn different speeds in 4 wheel drive and there's just no way around it. It's an overstatement to say they have to be the same. It would be really bad on pavement (you'd break something), but if you're knee-deep in mud you wouldn't even notice it. It'll be dangerous in the snow because you'll have one back tire spinning all the time and it'll be easier to break loose. Some judgement is called for, but in most cases you'd want to change them both.

Reply to
Joe

My cousin worked in a Montgomery Wards auto service thing 20 years ago. One day this woman drives in and says "my Husband stuck his finger in my rear end last night and it was dry as a chip". You can imagine that they just about hyperventilated laughing, and she was embarrased and didn't think it was funny.

Reply to
Joe

Instead of changing differentials you might consider installing larger tires if they will fit. This will effectively reduce your gear ratio though you won't get as good fuel mileage as if you had just done the gears. Worth considering though.

Andrew

Reply to
Andrew

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