Advice on GM 14 Bolt Corporate Full Float w/3.73 gears that are junk

Hi all, so now I am at the point that all my gears are shot in the rear-end of my truck. The dilemma is I am trying to save money here, and this damned truck project is starting to really get a bit expensive.

So now comes the part I need all new gears in the rear-end (it started with a leaking pinion seal). I would like to maybe find another good used rear-end and swap out gears, however that is also a risk if you buy from a yard and tear it all down only to find the gears are also junk.

The spiders in mine have a couple gears with internal grooves in them, and that same cross-shaft is also grooved. The pinion gear has a nice mirror finish (which is bad) & some major pitting on other teeth. The ring gear is the same. Bearings are pitting & de-laminated races....basically its all junk except the carrier.

What would you guys do on something like this where it would not cost much more than a few hundred and your on a budget?

Looking for suggestions on what to do and save money. (Maybe it is not possible..??)

I don't know if I've ever pulled a set of used gears that didn't have a nice polished finish on the teeth? I'm no expert, but I've never been very concerned with light abnormal wear on the spiders and cross pin, as they generally only see slow speed use unless doing a one-wheel-peel.

Got any pictures of the pitting on the pinion gear?

Post pictures of the gears if you can. I would go to a you pull yard to buy a rear. There should be a few to choose from - whether drw or srw, the guts are the same. Strip it down a bit so you can examine the gears and the differential. You may just be able to buy the guts. One problem you might come across if the rear end in your truck is really that bad is a spun bearing - or both on the differential. Depending on the extent of damage, the case may or may be able to be repaired.

Depending on source, you can get a full rebuild kit for about $150-200 and new ring and pinion gears for another $150-200. Its about $600 for a Yukon limited slip, $400 for a Grizzly locker, or $150 for new spiders. If you source the parts carefully, you can be at all new parts for about $300-450, which is about what a junkyard 14BFF goes for in most places.

@bucket I don't have any pics here on my PC at work, however in my thread there is a couple pics, not really good ones though. You can see the pitting on the ring gear somewhat, and the shiny on the pinion.


@Nonstop The bearings did not look spun at all on anything. Also with the above link is a pic of the axle opened up. It is dirty for sure, but looks in good shape otherwise. I thought about going to a pull yard to take a look at some, and would be afraid of all the work to pull it apart and have the same results, and a bunch of money into more junk.

@Bextreme04 I do need the full bearing/seal rebuild kit for sure. Was told that I need a new ring and pinion, and also the spider assembly. So basically $600ish for all of that.

I talked to a few other mechanics about this issue I shared with you guys, and I have the same opinion at this point that they do......clean up axle tubes & inside of axle, replace the pitted bearings, bad seals, clean up the grooves on the spider shaft, and just put the thing back together. Being a cruising truck (not pulling anything, nor high-horsepower engine) they feel I really do not have much to be concerned about.

I guess it depends on who you talk to. When I get to this guys house that will re-assemble it, I will get some good pictures of these parts and get them posted up for you guys to see. If these parts were at my house I would have already posted some.

Are you positive this is a FF 3.73 ratio axle? Most GM 14 bolt FF axles I’ve seen have been 4.10, and a few in 1 ton trucks were 4.56. The FF axles were used in heavy duty trucks, so they needed lower than 3.73. The 3.73 gears were more common in the SF axles.

75gmck25 said:

Are you positive this is a FF 3.73 ratio axle? Most GM 14 bolt FF axles I’ve seen have been 4.10, and a few in 1 ton trucks were 4.56. The FF axles were used in heavy duty trucks, so they needed lower than 3.73. The 3.73 gears were more common in the SF axles.

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Yes, 100% positive on FF & 3.73 gears.

I've had several 14ff's with 3.73 gears. Actually more of them than 4.10 gears.

75gmck25 said:

Are you positive this is a FF 3.73 ratio axle? Most GM 14 bolt FF axles I’ve seen have been 4.10, and a few in 1 ton trucks were 4.56. The FF axles were used in heavy duty trucks, so they needed lower than 3.73. The 3.73 gears were more common in the SF axles.

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It depends on the years and trim trim levels i believe, ive gotten ff rearends and both were 3.73 gears, quite bummed to say the least....

75gmck25 said:

Are you positive this is a FF 3.73 ratio axle? Most GM 14 bolt FF axles I’ve seen have been 4.10, and a few in 1 ton trucks were 4.56. The FF axles were used in heavy duty trucks, so they needed lower than 3.73. The 3.73 gears were more common in the SF axles.

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I've had numerous 3/4 and 1 ton Squares over the years and all of them had 4.10 gears with a 454. My current K30 has 3.73's with a 454. I think I figured about why the others had 4.10's was because they all had the Z82 factory tow package. The person that ordered this K30 for some reason didn't.

I wish I had 373's in my 14b ff diff. I have 410s or 456 and cant go very fast with that.

when you change your gears in the rear diff..........do you have to also change gears in the transfer case?

I have the Dana 44 in the front.

75BEASTK20 said:

when you change your gears in the rear diff..........do you have to also change gears in the transfer case?

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No,but you do need to change your front diff gears to match the rear.