Need some help with a d20 problem

[Nevadasmith]

So 3000 miles ago I rebuilt my Dana 20 transfer case, just bearings, and I didn't replace the center shaft.. I used black Molly grease for assembly lube, and filled it with Lucas 75w140, I spent a lot of time getting the pre load on the output shafts just right.
I knew my gears were trashed, but I put it together anyhow hopping for the best.
I pollished all the rust off with scotchbrite surface prep pads, and the intermediate shaft with 400 grit emery cloth.
3000 miles it has been flawless! Last weekend I had to make a 200 mile round trip, on the highway, 60-65 mph after about an hour on the road, I started hearing a ticking / clacking noise, almost gear tips hitting gear tips.

I pulled over the tcase Wich has never gotten hot before was way too hot to touch, checked the fluid, it was full, waited 30 minutes for it to cool down, got back on the road. Everything seemed fine no noise.

Happened again about an hour later. I changed oil when I got home, on the recommendation of a friend I used redline 75w250 shock proof oil. Test drove it for about an hour everything seemed great.
Yesterday I went to do some 4wheeling with friends 60-70 miles away, on the highway it started making a gear howling/humming noise light, but I could hear it.
Let it cool down, played on some rocks had a great time, seemed louder in 4 low than I remembered. But fine.
On the way home, it got louder I had to pull over 3 times in 60 miles, at 1 point I was floor boarded down hill to maintain 55mph looking for a spot to pull over.
I actually kicked the tcase into neutral, and if felt like I speed up.

I checked the oil it's still full but black and full of metal.
I know at this point it has to come back apart, but could it just be as easy as the intermediate shaft and bearings??? Or is the surface hardness of gears gone??
Best guess's please...
Sorry I'm so long winded on this one. Thanks in advance.

 

[Nevadasmith]

And is there a way to diagnose the problem through the inspection port?? Anything common to look for?

 

[broncodriver99]

Looks trashed to me. Why run such a heavy oil? Factory recommendation is 50W motor oil. 80w90 gear oil is about the same viscosity. You need the thinner oil for proper lubrication. I would find another t-case.

 

[Viperwolf1]

Looks to me like there was quite a bit of rust inside. Ground down rust in fresh oil is probably only slightly less abrasive than sand. You should probably look for another D20.

 

[Nevadasmith]

Yeah I figured I'd need a new tcase, just getting hard to find, but I see rebuild ones at the bronco houses for $625+ so I'll probably go that route.... thanks

 

[broncodriver99]

I have a couple but a little too far away. Try Driven Auto Parts, they are in AZ and probably have plenty. Or, throw up a wanted ad here. I am sure there are plenty sitting around on shelves.

 

[Hozr]

It'a all been stated above, but yeah, that oil was definitely WAY too heavy. I've been running 0W-50 race oil in mine since the rebuild with zero issues now.

 

[Nevadasmith]

So I found the problem, the cluster bore is worn out, allowing it to cock and corner load the thrust washer on one side only wearing about half the washer out.... misaligning the gears and letting the rollers skid.

Yeah I still need a new transfer case, if anyone else has those symptoms, I suspect that is the problem.

I'm hoping this is the solutionAdvance Adapters Dana 18 Transfer Case Intermediate Gear Kit 716005

 

[bronconut73]

Just make sure you don't use those uber thick gear lubes again.
Red line makes a 50 weight racing oil, but they also make a 75/90 gear oil which may be better in this scenario. But the factory did call for straight 50 weight motor oil.

 

[JB Fab]

DO NOT use a gearlube the sulfur based pressure additives attack the bronze thrust washers.

Use a 50wt motor oil or a 50wt manual trans oil.

https://lucasoil.com/products/transmission-products/synthetic-50-wt-trans-oil

 

[sykanr0ng]

Mobil Delvac 50 synthetic transmission oil, made for splash lubricated manual transmissions.
Rated for a 500,000 mile oil change interval in Eaton Roadranger transmissions. those come with a 750,000 mile warranty so you know Eaton is not going to recommend an oil that costs them money.

https://www.mobil.com/English-US/Co...XMobil-Delvac-Synthetic-Transmission-Fluid-50

 

[ptwist]

Im probably going to have to tear into my D20 as its super sloppy and leaks fluid like its a job. Anyone ever buy/run one of the re-man form Jeffs or the other vendors?

 

[Boss Hugg]

Yeah I figured I'd need a new tcase, just getting hard to find, but I see rebuild ones at the bronco houses for $625+ so I'll probably go that route.... thanks

I'd recommend the Teralow gear set. If there's nothing wrong with the case, reuse it with new, lower gears. From what little I can tell of the pics, it looks like the surface of the teeth are too far gone to depend on for long life. And since the cluster gear is gone... The TL gears are like $825 thru Wild Horses I think. If you were to HAVE to spend money, get some advantage out of it.

And I'm not sure anyone else said it ;D , use the 50wt! LOL.

 

[77-302]

Lots of articles out there regarding the proper lube for an all Gear D20 with brass bushings... I can see if I can dig up some previous articles I read. In short I chose Valvoline 75W-90 after reading countless articles comparing the various options based on cost, performance with yellow metals, additives etc etc.... I have not had any issues in over 5k miles.
Regarding cost for rebuild... I constantly searched craigslist to find a D20 as a donor. I used parts from my original and the donor, and new bearings to get the final version I have now... I found my donor D20 for $75 as the guy had it behind a barn and didn't even know what if came out of...

 

[Nevadasmith]

I'd recommend the Teralow gear set. If there's nothing wrong with the case, reuse it with new, lower gears. From what little I can tell of the pics, it looks like the surface of the teeth are too far gone to depend on for long life. And since the cluster gear is gone... The TL gears are like $825 thru Wild Horses I think. If you were to HAVE to spend money, get some advantage out of it.

And I'm not sure anyone else said it ;D , use the 50wt! LOL.

I'll check in to the Terra low gears, but budget wise that would have to be after Christmas, hahaha , but thanks

 

[Nevadasmith]

Lots of articles out there regarding the proper lube for an all Gear D20 with brass bushings... I can see if I can dig up some previous articles I read. In short I chose Valvoline 75W-90 after reading countless articles comparing the various options based on cost, performance with yellow metals, additives etc etc.... I have not had any issues in over 5k miles.
Regarding cost for rebuild... I constantly searched craigslist to find a D20 as a donor. I used parts from my original and the donor, and new bearings to get the final version I have now... I found my donor D20 for $75 as the guy had it behind a barn and didn't even know what if came out of...

Yeah I've been looking since I put this one back together...I knew it was on barrowed time, hence the heavy, then heavier oils. No luck, but I'm planning on attending the Wildhorses swap meet, maybe some one will have a tcase there or at least a gear set... thanks so much for for all the help!!!

 

[Broncobowsher]

That first pic of the trashed shaft, the tera low won't fix that. I am sure there are more damaged parts in there that tera low won't fix as well.

Find another transfer case, and put good parts into that.

Looks like your old case has spent time playing in water/mud. And was not maintained after the abuse.

 

[Huckit36]

Went out looking for some of that Lucas 50wt today and came up empty handed. Would some of the rear end 80-90 ive got sitting on the shelf already be just as good in my dana 20?

I said Lucas, but would have taken any 50. I am planning on swapping to a 700r4 and an atlas next year. Anyone know what fluid that takes? Figured I’d ask since I was already here asking question. Thanks

 

[Broncobowsher]

If it is a GL4 gear oil you are fine. GL5 doesn't like the yellow metals (bronze bushings).

 

[Huckit36]

If it is a GL4 gear oil you are fine. GL5 doesn't like the yellow metals (bronze bushings).

Thank you