You will absolutely get some binding if the TC is in 4WD. AWD has an open diff in the TC. 4WD TC locks the front and rear shafts together in 4WD.
What did you do to your NNBS GMT900 Tahoe/Yukon Today?
- Thread starter phattyford
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
if you are talking about the denali, if you figure out a way to engage a 4x4 front diff (either electrify the actuator or use a adapter) it will be no different than what is on it now
but not sure exactly what you are attempting here overall.
Well took an hour and 45 minutes from the time i left my house to back home to unbolt them and get em home.
Let me try again too better explain what im wondering.
If i just bolt these diffs in without changing the TC the truck will not move because the front diff is not locked in 4x4 mode.
If i put 12V to the front axle actuator to engage the 4x4 mode i believe it should drive the same as a AWD front diff. Right?
Let me try again too better explain what im wondering.
If i just bolt these diffs in without changing the TC the truck will not move because the front diff is not locked in 4x4 mode.
If i put 12V to the front axle actuator to engage the 4x4 mode i believe it should drive the same as a AWD front diff. Right?
As far as I know yes
Is it a plunger type actuator that just has one signal to move it or is it a screw drive type that would be more involved? I know the older ones had thermal actuators. Check the wiring diagram or you can unscrew the actuator easily to investigate. I thought there was some kind of aftermarket part or trick to keep it engaged full time but I am not positive about that.
I'm not sure how the internal part of it works. I do know when engaged it is from a 12V source.
With the 261 TC there is a switch on the top that supplies power to the actuator when 4x4 is engaged.
I can go to the little no name wrecking yard near me and get the wiring i will need to supply the TC with power and then hook it to the actuator.
The only reason i ask that question was because changing both diffs takes some effort and i might wanna wait a day or two before changing the TC and also incase i did not have one yet but tomorrow im going to go pick one up.
With the 261 TC there is a switch on the top that supplies power to the actuator when 4x4 is engaged.
I can go to the little no name wrecking yard near me and get the wiring i will need to supply the TC with power and then hook it to the actuator.
The only reason i ask that question was because changing both diffs takes some effort and i might wanna wait a day or two before changing the TC and also incase i did not have one yet but tomorrow im going to go pick one up.
mikez71
Full Access Member
- Joined
- Mar 9, 2023
- Posts
- 3,219
- Reaction score
- 3,985
OK I see what you want to do...
Drive with the open diff AWD X-fer case, with the 4WD front axle.
So if you actuate the front axle (typical 4-HI or 4-LO mode), it should be an open differential in front.
Front is NEVER a locker, sorry for my confusion. Should be fine?
Drive with the open diff AWD X-fer case, with the 4WD front axle.
So if you actuate the front axle (typical 4-HI or 4-LO mode), it should be an open differential in front.
Front is NEVER a locker, sorry for my confusion. Should be fine?
Last edited:
Drained the oil and removed the rear cover off the rear diff and im pretty happy with what i found/seen.
There was a little water in it from sitting for about a year with the vent tube open. Guessing maybe a cup. The gear oil still had a green tint to it but not bad by a long shot.
The magnet had a little of that real fine black stuff on it. I have seen way worse!
Everything seems to spin fine and i can get it to lock spinning one axle holding the other stationary.
Tomorrow need to get an axle out so i can figure out what seals to order along with new brakes.
Drained the front diff and the gear oil came out looking nearly new and very little of that black stuff on the magnet. Truck came from southern California so maybe 4X4 was never used?
Just going to clean it and run it as is.
If i had bought these from a wrecking yard i would assume they are from a very low mile truck.
Question about the rear Universal joint.
I have some straps for a 10 bolt rear end. When i hold the strap up to the 14 bolt yoke the holes line up and bolts on fine.
Does that indicate the stock joint will work or not?
There was a little water in it from sitting for about a year with the vent tube open. Guessing maybe a cup. The gear oil still had a green tint to it but not bad by a long shot.
The magnet had a little of that real fine black stuff on it. I have seen way worse!
Everything seems to spin fine and i can get it to lock spinning one axle holding the other stationary.
Tomorrow need to get an axle out so i can figure out what seals to order along with new brakes.
Drained the front diff and the gear oil came out looking nearly new and very little of that black stuff on the magnet. Truck came from southern California so maybe 4X4 was never used?
Just going to clean it and run it as is.
If i had bought these from a wrecking yard i would assume they are from a very low mile truck.
Question about the rear Universal joint.
I have some straps for a 10 bolt rear end. When i hold the strap up to the 14 bolt yoke the holes line up and bolts on fine.
Does that indicate the stock joint will work or not?
I'm confused, any would an open front diff bind when turning? mine has 4wd and it doesn't bind one bit without being in 4lo which I guess is locking the diff.
running it open would be fine, if you one tire spins badly and your tc is still active it should brake that wheel to slow it down transferring tq?
running it open would be fine, if you one tire spins badly and your tc is still active it should brake that wheel to slow it down transferring tq?
I would question if that 4wd is working properly, it will absolutely bind in a turn, especially on pavement. That is the whole point of 4wd.
not the same as AWD or "auto"
I think I'm not understanding what you mean by locked diff. I think of that is locking the left and right wheel together. that will definitely bind while turning. but open, it should now. you can apply power into the open front diff without locking the wheels together.
do these also unhook the diff input from the pinion?
the front diff is a open diff no matter what the setting, the rear diff such as a g80 is normally open but will lock when there is one rear wheel spin at a difference of 15mph from the other side.
then throw in stabiltrac and traction control
the result is a big mess but it works most of the time.
if you get into a situation where the system is hindering you, then pull the abs fuse, after you get thru wherever you are going or get unstuck then put the fuse back.
Front diff is always an open diff weather it is AWD or 4x4 diff
When the 4x4 diff is put into 4x4 mode then the diff is still an open diff but the pass side axle is locked into 4x4 mode and along with the two speed transfer case power is supplied to both front wheels.
I guess i assumed when i said front diff locked it would be automatically known i was talking about 4x4 mode and with an AWD transfer case it should act like a normal AWD front diff because an AWD diff is basically always locked in 4x4 mode.
When the 4x4 diff is put into 4x4 mode then the diff is still an open diff but the pass side axle is locked into 4x4 mode and along with the two speed transfer case power is supplied to both front wheels.
I guess i assumed when i said front diff locked it would be automatically known i was talking about 4x4 mode and with an AWD transfer case it should act like a normal AWD front diff because an AWD diff is basically always locked in 4x4 mode.
Got the NP261 TC today and i think i better rebuild it. I does feel a little loose and the input bearing feels a little rough.
Should need new bearings, chain, bushings and seals and a case saver.
So far im into this swap $650. Probably going to be another 5 or 6 hundred in new parts.
Not to bad so far i don't think. I know my trans is going to love climbing in 4lo though!
Should need new bearings, chain, bushings and seals and a case saver.
So far im into this swap $650. Probably going to be another 5 or 6 hundred in new parts.
Not to bad so far i don't think. I know my trans is going to love climbing in 4lo though!
- Joined
- Aug 2, 2018
- Posts
- 10,303
- Reaction score
- 14,923
A while back, I developed a strong pull to the right when braking at highway speed. Since the pads and rotors were new, the calipers were checked out and re-lubed. The pull to the right was reduced, but not eliminated, so I had both front calipers and hoses replaced. Now, the truck brakes in a straight line.
Dirty looks
Full Access Member
- Joined
- Dec 5, 2025
- Posts
- 118
- Reaction score
- 211
148ft lbs clydeI had a stern talk with my mechanic today about adequately tourqing bolts so he doesn't kill me... I'm the mechanic.
Been there but not by my doing. Did it lock up the wheel every time you braked?I had a stern talk with my mechanic today about adequately tourqing bolts so he doesn't kill me... I'm the mechanic.
When that happened to me I was driving my dad’s late 70’s w200 dodge EC. He was a heavy equipment mechanic so he had a utility bed packed with enough tools and tid bits of parts and nuts and bolts and such.
His lf caliper did the same thing. Bolt fell out. I’m was able to macGuyver it using what was on board to get going again. I was a teenager.
His lf caliper did the same thing. Bolt fell out. I’m was able to macGuyver it using what was on board to get going again. I was a teenager.
