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I just bought a 7.3. It's on 38.5 Baja claws which are worn out. When I bought the guy selling it said it was regeared but didn't know what years were in it as he was the 3rd owner. How can I tell what's in it? Also I am putting new wheels and tires on it. 37x13.50x20, what gears should I have in it? I just bought a 6000lbs boat. I want to tow but still be able to drive down the highway at decent speed. Right now it will rip a house down but 2000 rpm around 65? Hard to tell because it's not recalibrated for the tires.
 

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I just bought a 7.3. It's on 38.5 Baja claws which are worn out. When I bought the guy selling it said it was regeared but didn't know what years were in it as he was the 3rd owner. How can I tell what's in it? Also I am putting new wheels and tires on it. 37x13.50x20, what gears should I have in it? I just bought a 6000lbs boat. I want to tow but still be able to drive down the highway at decent speed. Right now it will rip a house down but 2000 rpm around 65? Hard to tell because it's not recalibrated for the tires.
Use a gps to know your true speed is, and match against your speedo, if you have a smart phone, iphone or android, search for gps speed app.

But the gear numbers should be stamped on the gear when you open your diff covers, at least my stock 3.73 were.

Sent from tapatalk PRO ........ I WISH
 

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I just bought a 7.3. It's on 38.5 Baja claws which are worn out. When I bought the guy selling it said it was regeared but didn't know what years were in it as he was the 3rd owner. How can I tell what's in it? Also I am putting new wheels and tires on it. 37x13.50x20, what gears should I have in it? I just bought a 6000lbs boat. I want to tow but still be able to drive down the highway at decent speed. Right now it will rip a house down but 2000 rpm around 65? Hard to tell because it's not recalibrated for the tires.
If you don't know what gears you have, start with the tag on the rear diff cover. In the number sequence, you will see 3 L 73 or 4 L 10 which would indicate 3.73 LSD or 4.10 LSD. If there is no tag, and with out pulling the cover and if you have a limited slip (it's easier) mark your yoke with a white paint pen with zero mark and mark the 12 o'clock position on your rear tire, with the rear on jack stands. spin your rear tire (while watching your mark on your yoke) objective is to spin 1 revolution on your tire and count the number of times your yoke spins from the position it started.
example: if you spun 1 revolution and your yoke spun a little over 4 times, then you could have 4.10's ... a little more and you could have 4.30's . spun 4 and half times = 4.56's.
Hope this helps
obviously the most fail proof is pull the cover, and look for the ring gear count and pinion gear count. divide ring gear by pinion = final gear ratio.
As far as what ratio you should have, It depends what you do with the truck. you can't have the best of both worlds....either you tow more or cruise on the freeway more.....If you were towing heavy loads than 4.56 would be a good choice. If you want more freeway speed cruising, than 4.30 might be more to your liking.
advice - if changing gears, use American made gear parts for gears and bearings - like U.S. gear Dana Spicer and Timken bearings
 

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Awesome. I'll pull the diff cover tomorrow and see what I can figure out. I'll probably be back on here with more questions.
 
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