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Discussion Starter · #1 ·
ok guys i have a 06 gmc with cognito 7 inch lift on it and need some input.
it has burnt up the front pinion bearing in less than 20,000 mile on a pavement pounder. has anyone else had this problem the obvious cause is the angle of the front diff causing oil starvation of the front bearing. after speaking with justin-owner designer-at cognito he says im smokin something and hes never seen this before. it has destroyed the front diff housing included and that took out the tcase this is rather expensive and i highly doubt no one else has had this concern so pipe up anyone else???????
thanks.
 

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Who installed the lift? When I put my TC on, in the instructions, I was required to add some fluid to the front diff to compensate for the angle as a result of the lift. I think I had to add a 1/2 pint or something. It's been a while but I know we added some, was a PITA to squeeze through the hose to get it in. But I agree with Swampfox, what was the level to begin with? I would say that is the first place I'd start.
 

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I'll pipe up ...:D I like that...

So are you running a stock front drive line or a CV?
How many miles are on your truck?


There can be many reasons why this happened so let get some more info from what is on your truck and go from there.
 

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Discussion Starter · #6 ·
truck has just over 20k oil level full always serviced twice allready its not my truck its a friends im just fixin it. t case syncro trashed due to siezed front diff unable to engage.
was overfilled by about 1/2 quart. after the diff was on the bench i straight lined the fluid level and its along way from getting the pinion bearing. and no it does not have a cv driveline. and no it didnt vibrate and or it wasnt driven over 25-30 mph in 4wd [which by the way is the most rediculus thing ive ever heard] the bearing was starved for oil. and so far im not much impressed with this setup and im glad its not mine.ill post pics tommorow sometime im interested to see what the response of the owner of cognito has to say then.
 

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Post pictures please.
Thanks.
 

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truck has just over 20k oil level full always serviced twice allready its not my truck its a friends im just fixin it. t case syncro trashed due to siezed front diff unable to engage.
was overfilled by about 1/2 quart. after the diff was on the bench i straight lined the fluid level and its along way from getting the pinion bearing. and no it does not have a cv driveline. and no it didnt vibrate and or it wasnt driven over 25-30 mph in 4wd [which by the way is the most rediculus thing ive ever heard] the bearing was starved for oil. and so far im not much impressed with this setup and im glad its not mine.ill post pics tommorow sometime im interested to see what the response of the owner of cognito has to say then.


-The truck only has 20k and the front diff fluid has been changed twice? Has someone installed a new set of gears in it?

-You said it was over filled by 1/2 quart but then say the fluid level is far from the pinion bearing?

-On front vibration, I am not sure why you would say ridiculous. Its called u-joint angles and when you lift a truck and have heavier u-joint working angles sometimes there will be a u-joint bind and that is reflected in vibration. Many people that use there truck in 4wd at higher speeds will get this and a new drive line with u-joints that are made to handle the heavier angle.

-You stated that this hole problem was caused by front pinion angle from the lift. That can not be true because the front drive line doesn't spin (other than idle rpm) when in 2wd. So when stating the bearing is smoked in 20k I don't think the truck was in 4wd the hole time. Also the front diff has a oil channel that pushes oil up to the pinion bearing. So if the ring gear & pinion spins it automatically lubricates the pinion bearing.


What we have seen is where someone has opened the diff and resealed it
with too much silicone. The silicone will brake off inside of the diff and float around until it plugs/stops flow of the oil passage that lubricates the pinion bearing.


Hope this helps you with your issue's.....


Nor-Cal Nick
 

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Discussion Starter · #9 ·
pics

ok
1- anal about his truck thats why serviced twice and we work at a dealer it cheap.

2- i understand driveline angles and that is not what caused this and has no bearing on this issue.

3-a diff rotating at slow speed in 2wd still needs lube on the bearings right? and this truck has maybe a lifetime total of 100-150 miles in 4wd.

im sure this lift is great in sunny california where 4wd is a status symbol but in reno we get snow and need 4wd. and also after reading cognito's install instructions for the lift there is no mention of ANY need for overfilling the front diff so look at the angle of the front diff in relation to lube level [stock] and tell me how you expect oil to supply that front bearing.

4- here are pics as you can see [maybe pos cell pics] bearing dry, race spun in housing, no silicone blocking passage, andd no gears have never been changed housing never opened before yesterday.


I would like to say im not attacking anyone here i am just curious if anyone who actually uses their 4wd has had an issue with this lift system.
specifically the front diff.
 

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Why would the pinion be turning in 2wd? Thats what the CAD is for.
 

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Discussion Starter · #11 ·
figured out exact cause

the exact cause does turn out to be error on the last person who serviced the front diff. when the diff is in the truck with the lift at the angle that the front diff is at the stock fill plug will only allow about 1 qt of oil to the diff before it spill out, which to a jiffy lube tech and or inexperienced
lube tech that doesnt realize that it didnt take enough send it down the road. so note owners of cognito lifts make sure that they are filled
to factory amount plus a little. and with a full two quarts it will allow fluid
to reach the bearing. still f''d up but at least it can be avoided.
 

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So it was low not a 1/2q to much?

Well I know you said that you guys get a ton of snow so look into a new front driveline. If you guys are hitting some higher speeds in 4wd then its worth the money.
 

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I use my 4wd at least once every month in the sand. I use it to tow in the sand and also use it cruz the dunes. I have not had a problem with it yet. Maybe my installer checked all those things and knew what they were doing and avoided that problem. Not sure???
 

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no problems on mine.installed it myself and did 4.56's. i estimate about 800-1,000 miles in 4x4 sometimes at 25-30 mph. just filled it to the drain plug level.
 

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The front shaft spins fast enough in 2wd in some trucks that a CV shaft is needed even for a 4" lift, Had 2 with vibe issues that CV shaft cured... 1 is an 06,1 an 07.5, both diesel
 

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many people have complained about a growling noise when in 4 wheel drive running about 25-40 mph. noise is usually more pronounced when the accelerator is let off. this is usually with lifted trucks.


i have said numerous times, that this is probably due to the diff bearing not being lubed enough. the rotation of the diff when a lift is installed does not allow enough lube to be put it through the fill hole.

i experienced this same failure with my old truck. the fix is to add more fluid!! i came across a thread a long time ago that said to add fluid through the breather plug so it starts to trickle out. if fluid is just added through the fill hole, there will not be enough

good luck:eek::
 

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Discussion Starter · #18 ·
just make sure when you fill them that it takes 2.0 quarts and all is good otherwise sooner or later it will burn down.
 

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Just had the same problem on my 08 with 4800 miles and 7-9 Cognito, first it was vibration at 70mph from the rear, came to find out was sent wrong lift 5.5 degree needed a 3, second terrible vibration in 4wd at speeds above 20mph, needed driveshaft I guess because 20 is apparently "high speed" in there opinion, and latest problem smoked front diff from dry bearings with 4800 miles. I thought I spent good money on the best lift out, have had rancho's for 15 years and never a problem and spent half this money. Lucky for me my dealer has covered all this under warranty but why so many problems with such a "high end lift" I am about ready to take this pile back off I am getting so frustrated.
 

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So Cognito lifted trucks need 2 full quarts, how much is in there normally so I know how much more to add.
 
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