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Gear change from 3.73 to 4.xx?

869 views 3 replies 3 participants last post by  shaggy 
#1 ·
My '99 250 is primarily a hauler at this point, although after selling some other cars it will end up being a daily driver as well.

I'm sure the truck has now 3.73 posi (according to axle codes) and it appears unmolested.

Of course, hauling my 5iver engine isn't in the power range really lock-up in 4th. Running 3rd and lock-up pulls me up just around 2500 rpm.

I haven't pulled any mountain passes or anything yet, just the usual "hills" and such around here near Portland.

Would it be worth a gear swap for towing, to ease load on the engine, trans and such?

How much cash should I expect to shell out for a gear swap?
 
#2 ·
What size tires? In most cases going to a 4.10 is all that is desired. I got a quote to do a tru trac out back and front and new ford gears installed for $3600
 
#4 ·
4.10 should be a good swap for you. I wouldn't recommend going over a 4.10 gear with that size tire. My girlfriend's truck is a '02 cc lb with a good bit of performance mods (exhaust,intake,tune, injectors, bigger turbo, and ATS tranny package) and she has 4.10 in hers and running 285's. She pulls a 4 horse slant gooseneck almost every day (hense the gear change) and it pulls great down the highway and when its in some big hills. Almost dont know its back there. Drives great unloaded too. So thats what i would recommend. I feel like a 4.56 will be too low and jack the rpms up too high. The only downside, 3.73 to 4.10 isn't a huge jump so change wont be as noticable as say coming from a 3.55. But defiently still worth it if you will be towing alot.

We just used hers for a trip out to Utah from SC. 4,400 mile round trip with an 18' flatbed loaded down with 5 atvs and the bed full of a weeks worth of gear/food. Rarely had to take it out of OD except for the big mountain pass near AZ border. EGT's rarely crept above 1000, saw 1200 on the bigger hills but nothing major.

As for cost, i recently had to rebuild my rear axle for roughly $1500 out the door. That was for new gears, bearings and seals, new factory ford trac loc, fluid, and labor. Also, i had swapped a junkyard axle in 2 weeks before as a quick fix so i could drive it so labor was also for bolting in the new axle. You would be closer to the $1000 or less for the rear since no trac loc/carrier is needed. The front is a tad more expensive due to more being involved it pulling it apart. Mine is an E99, 4" and 315's, ZF-6, and 3.73. Nothing done but straight pipe and 6637 mod and it pulls fine, though 4.10's would be nice.

Sorry for the long response. Ive worked in a 4wd shop and been in the 4x4 scene for a while so i have a good bit of expeience with different gear ratio/tranny/motor combinations. feel free to shoot me a pm if you want any more details.
 
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