2nd Gen Non-Engine/Transmission 75k miles, differential cluster gears, left cluster gear only is scratched, ideas?

[rweis]

Ooooooook, 75k miles orgional owner



Tom (mechanic) got the axle and took off the cover.



Next question.



The spider gears look fine, the ring gear looks fine, right side cluster gear looks fine, BUT the left side cluster gear has some longitudional scratches on many of the teeth about 1mm - 2mm deep. The spiders are clean. Only the left side gear has these "looks like a scratch down the length of the tooth" and in the area where the left gear engages the spider gears (but the spider gears are smooth).



Very odd.



What alearted us was an abnormal amount of metal filings on the magnetic dip stick. With the Mag-Hytec cover I have about 8 qts of fluid and it was full (I check it about every oil change for level and filings etc). I also have a temp gauge on the diff and it rarely has been even up to 180* absolute max towing in the mountains, normally 160* towing, 120* empty.



No other gear has these longitudional scratches on it. Each tooth on the left side gear has at least 1 scratch, some several scratches.



The SM says if a gear has a scratch on it to change that gear an go on with the rebuild.



Tom wants to look at the big pin that holds the spider gears to see if there is any wear (tommorrow).



Ideas? Looks like surface failure to me.



Bob Weis

 

[Extreme1]

That is odd, you might be accurate with the surface failure theory. Do you have access to a hardness tester? If you haven't removed the carrier I would check the bearings. Test the ring/pinion clearance with a dial indicator before teardown, if it's loose get bearings. If not, don't bother but I'd still take a look.

 

[rweis]

Well, it will be a rebuild kit for my Dana 80 cluster gear set. He thinks it is surface failure also on the left cluster gear. The other cluster gears seem ok, but we are replacing them all. That should make this a pretty well rebuilt rear end.



The moral of the story is to have a magnetic dipstick or some sort of a way to see the extent of the metal contaminent. If there is considerable contaminent, then "something is happening to cause it" and you have to go in and find the problem.



I happened to be changing the ring gear and pinon while it was apart, but none the less it needed to be taken apart and investigated.



I think we killed 2 birds with 1 stone. A metal fatigue problem as well as a ratio change.



Now the next question for the readers.



The speed sensor is easy to get to with the axle out of the truck. I have not had any problem with it. Would you change it? Does it ever just fail? A lot easier to replace now. Your thoughts.



Bob Weis

 

[rweis]

Well... ... ... ... ... . the saga continues



The carrier bearing on the passenger side had be spinning its race, sooo... a new carrier as well. Something about when it rains it pours



However, better to find out now than when towing the rv out in the middle of no where.



Let's see, rebuild the fuel system, rebuild the differential, rebuild the fuel cannister, all NORMAL maintenance at 73k right?, oh, and replace the VP44 - but that was on DC's nickle.



What are the chances I can get DC to recover ANY of the parts cost? I can take the dammaged parts to them.



Bob Weis

 

[SnoKing]

Awaiting your road report on how you like the 4:10's. SNOKING

 

[scotmartin]

Interesting. Makes me wonder if the bearing failure was the cause of the damaged gears. Maybe parts of the bearing hit the gears and damaged them. Or maybe I have it backwards. Or they might have both failed at the same time.



Any ideas?

 

[rweis]

Just Tom's theory,



Under heavy load the inner race on the carrier left side bearing would intermittently spin. The shims showed spin score marks and were several . 001's too thin. Tom thinks the proper preload was not set initially but only had an effect when heavily loaded.



The carrier bearing left inner race that should have several thousanths press fit has zero press fit. That race can easily be removed by hand. The outer race seems to be fine. The right carrier bearing inner race is fine. The left bearing only has very little dammage markings. Minor pitting, no major failure. The other bearings have only minor damage, mainly normal wear, no failure.



I think the Mag Hytec magnetic dipstick might have been a major player preventing major bearing failure. Yes they need to be replaced, but did not fail outright. Tom also thinks the larger capacity of 8 quarts might have minimized damage with a significantly larger fluid body and along with the magnetic dipstick kept catastrophic damage to a minimum.



However he also does not think that the bearing gear system would have gone much more than another 25k at the most. With heavy towing less than that.



I asked him about the offset of the ring gear from 3. 54 to 4. 10 without changing the carrier to the 4. 10 carrier. He said the company that makes the thicker replacement does so knowing the different amount of offset needed. He did not exactely measure the different thickness, but thought it was less than 1/2" and more like 1/4". We laid the 3. 54 and the 4. 10 side by side and eyeballed them and it looked like about 1/4". I told him theye are some here on TDR that expressed serious concerns about not changing to the 4. 10 carrier to compensate for the difference. We are staying with the 3. 54 carrier and the 4. 10 ring gear / pinion.



Soo..... By changing the rg & p now we caught and prevented major damage. I will have a new carrier, cluster gears, bearings, ring gear and pinion. We are also changing the wheel bearings just in case they might have abnormal wear from the metal filings in the fluid.



I should have it back by next friday and will give a prelim thought on the 4. 10's and we are going to tow over Christmas holidays and will add that observation then.



Bob Weis

 

[rweis]

Well, gear swap done.



Remember that carier inner race that had spun the bearing? I took the carrier to dodge with the paperwork thinking that DC would warrantee it. NOPE UNLESS DC does the work. Stupid me, I thought a warrantee was a warrantee.



So for the additional $500 shop labor DC would have charged and would have warranteed the carrier ($175 cost), I am glad again that DC has only touched my truck 1 time.



Tom showed me the setup as he set it up. Really a nice job. Very pleased with the quality craftmanship.



So far I have only driven unloaded 125 miles. I see the diff temp is 30* higher than normal as the gears lap in (165* vs a normal 135*). Manual says 500 unloaded miles prior to towing, then be extremely carefull with heat buildup towing. Change fluid at 500 miles as well to clean out any "stuff, metal filings or phosprous coating from the gears".



Drivability is very good. I have a KSB1-B and it is a heavy shaft turbine and somwewhat laggy. With the higher rpm / mph the boost (cruiseing) is about 2 # greater (puts cruise boost @5 psi) and makes the turbine much more responsive. The biggest part of turbo lag is at the beginning of the lag range, once it starts to spool and gets moving the lag is very short lived.



I am going to do a 250 mile interstate drive tommorrow and will report any differences from the above. I am going to tow about 200 miles next weekend and will see how the temps go (towing temps typically 20* higher than unloaded temps)



At 60 mph the rpm's = 1875 and the engine is turning in a comfortable range (sweet spot I think is 1800 - 2100). You have to be comfortable driving at not much higher than 60 - 65 mph to do the 4. 10's comfortably I think. I am so it is fine with me (our tires are only certified to 75 mph I think).



I know the overhead mpg avg is only a mark (as it is far from accurate) but strangely the avg mpg has increased 3/10ths. It should be about 20% less. Not too sure what the deal is. Maybe less time in low mpg's during normal acceleration from the 3. 54's. Strange, but will see what the longer trip will do. The cruise instant mpg readout (I know this is not an accurate figure, just the difference) is down from 33 mpg (55 mph, 3. 54's) to 30 mpg (55 mph 4. 10's) which is about right. True hand calculated mpg is 16 mpg for 73k miles (overhead shows 21. 0 average during same drive everyday (about 25% error probably due to the DD2's, ie different APP angle (different amount of fuel) for mph)).



Overall very satisfied,



Bob Weis

 

[rweis]

First 200 mile tow (now 700 miles on the gear set):



I LIKE IT, I LIKE IT!



1900rpm = 60 mph IN O/D. Much better pulling ability on hills. You can always come out of O/D if you really need to get into it. BUT, if I drive 60 mph regularly. IF you regularly drive 75 mph then this may not be your gear set. There is a trade off of speed for torque.



EGT is about 100* less (higher rpm's), KSB1-B spools up much better as it is at 10# boost just driving along (60 mph in O/D) and therefore already spooled up and ready to go.



I know overhead is not correct, but 3 better mpg towing (lower rpm's, were 2400, now 1900)



Overall overhead now about 1. 5 mpg less (about 10%) average after 700 miles.



Differential fluid temp still a little high about 220* at 60 mph. Might take some time to really break in the gear set. I will just change fluid frequently to keep the oil fresh. I did check the magnetic Mag-Hytec dip stick and it had some fuzz on it. Not a lot, but some, so there is a lapping process happening.



I would highly recommend that you start out with 4. 10 if you tow heavy, and not have to do what I did to correct my initial error in the initial purchase of the wrong gear ratio.



Bob Weis