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87 k5 front differential gear ratio

J

jonmfnjones

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Hello and thanks for viewing. Just purchased my first k5 and was told that the previous owner had installed 373 gears in the rear end but left the front differential ratio stock due to money restrictions . After researching my gears it shows I have 28 spline ring and pinions but when trying to order replacement 373 gears from Randy's to match the rear it keeps pulling up 30 spline. Why is this the case and what do I need to do to insure I get the correct gears?
 
Spline count shouldn't matter for just a R&P swap. I am assuming the stock gears are 3.08 so the carrier won't need to be swapped. Just pick up a 3.73 gear set for your axle (Corporate 10 bolt 8.5" or Dana 44) and a master install kit.

The spline count is in reference to the side spider gears that the axle shafts mate to inside the carrier. Older Dana 44/10 bolt were 28 spline up until 88ish when they upgraded the 10 bolt to 30 spline inner axles.
 
And actually now that I think about it before you order anything I highly reccomend that you pull the diff covers and verify what gears are in each end.

Previous owner may have blown up the rear and replaced 3.73's (which were optional gears)

Front gears could be 2.73 which I think will require a carrier change or thick gears.

Always better to verify what you've been told by the previous owner because a high percentage of them have no idea what they are talking about.
 
MTBLAZER89 said:
And actually now that I think about it before you order anything I highly reccomend that you pull the diff covers and verify what gears are in each end.

Previous owner may have blown up the rear and replaced 3.73's (which were optional gears)

Front gears could be 2.73 which I think will require a carrier change or thick gears.

Always better to verify what you've been told by the previous owner because a high percentage of them have no idea what they are talking about.
Click to expand...

X2 :popcorn:

also, where in Oklahoma are you?
 
Thank you for the reply fellas. I will definitely check out the diff before i order anything! I am new to owning a 4x4 that I will be doing my own work on so any advice is appreciated! I live in Ada Oklahoma and bought the truck from a kid down by fort Worth. I'll tear into it this evening or tomorrow and verify what is in it. Thanks again!
 
once you find out the ratio, it might be cheaper to buy a front or rear to match whichever has the better ratio. if neither do, it might be cheaper to buy a set of used axles than to spend the cash on new gears.
 
Carrier break for a 10 bolt is 2.73 and up and 2.56 and down. Spline count only matters if you are replacing shafts or putting in a locker. You should have an 8.5" 10 bolt. All ya really need to know. Unless you actually have 2.56 gear ratio
 
I was thinking the same thing. The guy just had the rear end rebuilt with Yukon offroad 373 gears with posi so I've got some feelers out on Facebook looking for a front axle with the 373. Haven't found one yet. Does anyone know what vehicles if any came stock with them that would fit my truck I'll go look at salvage yards
 
I might have a set I will check only way to know for sure is to pull the cover.
 
Okay so I went ahead and bought a Dana 44 front end with the 373/gears in it instead of doing a gear change. This front end has lockers on it and my question is this. I can engage the lockers on both sides and turn the pinion and only one side is spinning. I then turned each rotor by hand and again only one side spun the pinion. With them locked they should both spin together correct? If so how can I tell if it is a bad locker or broken axle?
 
Thats normal. Those are manual "locking hubs" not lockers. They engage the axles to the hubs for engaging 4wd.

A locker as typically referred to is a locking device inside the diff that locks both sides together.

Yours is an open differential which will spin one side like you are describing. Bind up one side and turn the pinion, the other side should spin and vice versa. It's just the way an open diff works with the spider gears and what allows each tire to spin at a different speed while turning.

Now if you bind up one side and the other doesn't spin then you need to look and see if the shaft inside is spinning. You'll be able to see the u-joint at the knuckle. If thats spinning then a hub might not be engaging. If the internals aren't spinning then there may be more issues.

Try what I said and post back up.
 
Thank you mtblazer89 it was definitely a rookie mistake on my part! My understanding of the "lockers" was off base. I did the test you said and it is working perfectly! Thank you again. I put a new wheel seal and bearing and a front seal on it today and plan on swapping out the front ends tomorrow!
 
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