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Diagnose this:

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazinaire, May 3, 2002.

  1. Blazinaire

    Blazinaire 1/2 ton status

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    I have a 208 T-Case and 700R4 and 6'' lift. When my truck is under a light load and I am light on the gas (cruising at 15mph in sand with 5psi in tires) it will make a noise like a bad u-joint in the driveshaft as it shifts from 2nd to 3rd gear. It sounds like it is coming from the T-case. I have the stock rear shaft and will be upgrading to a c/v soon, but all of the u-joints are good. I will eliminate the transmission as a possibility because it was factory new 40k ago and has a warranty still. Could this noise be the splines on the slip yoke wearing out and slapping around? Also when I accelerate hard on pavement, I sometimes hear what sounds like forgetting to push in the clutch while shifting with a manual. My rear axle is all new so it isn't the ring and pinion. The output shaft on the t-case looks good, but I don't know how to tell how tight the splines should be from the shaft to the slipyoke. PLEASE HELP!
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm not quite sure what you are describing by the noise, but from your description, I wouldn't rule out the TCC solenoid in the 700 if you are still running lockup. They can cause some weird problems, and its easy enough to diagnose, unplug the connector on the drivers side of the tranny, and drive it for a few minutes. Don't leave it unhooked for a long time (generates extra heat) but you can test drive with it disconnected.

    Just because somethging is new, do not rule it out.

    Again, my idea isn't likely, but its so easy and quick to try it's worth a shot. There isn't much more than what you can see under the truck, thats as easily tested for problems.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I was about to jump in and say just because something is new do not rule it out as not being bad, but you beat me to it. Most of the time it is the "NEW" things that are actually causing the trouble.
     
  4. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    First off, just cause your tranny is oem built dont rule that out, 700r4's are not made for 4x4 abuse unless you build them with corvette kits. they go POOP! Second, do you ave a 2 piece rear driveline? if so, is it sloppy where the splines go together? ( rock up and down to check it ) if it sloppy there, itll give that kind if noise, i know! it took me 1 F*%#@ year to diagnose that darn noise. good luck!
     
  5. Blazinaire

    Blazinaire 1/2 ton status

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    what will happen when I unplug it?
     
  6. Overkill

    Overkill 1/2 ton status

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    It will just prevent your torque converter from locking up (4th gear)
     
  7. Blue85

    Blue85 Troll Premium Member

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    But if you are running in 4WD, you will not get any lockup unless you use OD. The problem is described as occuring in the 1-2 shift, so this is really unecessary. Just use 4WD and keep the shifter in "3".

    The description is sand and 5psi, which to me means 4WD. Are you really running in 2WD so that the whole front driveline can be eliminated?
     
  8. Mudstud

    Mudstud 1/2 ton status

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    Be more specific on what it does in 2 wd and 4 wd. When you give the rear shaft the ol' shake shake shake test be sure the wheels are blocked and it's in neutral. Also, does the 4x4 shifter 'feel' differently as you shift the tranny going down the road?
     
  9. Blazinaire

    Blazinaire 1/2 ton status

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    And yes it does still mean 2wd. I have my front shaft out due to my 3.42's in the front and 4.56's in the rear, so the 4wd part can be eliminated. It really does sound like slop in the slip yoke/output shaft.
     
  10. Blazinaire

    Blazinaire 1/2 ton status

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    And it is occuring right before the 3rd gear shift (still in 2nd) but after it shifts the noise disappears. The shaft doesn't shake when I do the "shake-shake" test (I just put had both u-joints replaced)
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    If the torque converter clutch solenoid is failing and/or acting up, it can lock/unlock at any time it wants. If it never actually applies, it probably won't matter (as in never getting into 3rd or 4th gear in 2wd) but a failing TCC solenoid will cause stalling in 1st gear...if the TCC is chattering or the converter is locked up on a shift, it will firm up the shift, and I would imagine a firmer shift might magnify any slop in the drivetrain, no?

    I don't imagine its likely, but its *so* easy to check and the TCC solenoids are failure prone enough IMO to eliminate the easy stuff first.
     
  12. Blue85

    Blue85 Troll Premium Member

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    If the solenoid tends to stick, unplugging the connector will not eliminate that problem, just decrease it's likelyhood by not asking the solenoid to close. To eliminate it, you have to pull the pan and take the solenoid out. Old ones can tend to stick shut.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    If the solenoid doesn't lock in the first place, it can't stay locked. Thats my point. Typically they start sticking when the tranny is hot, such as coming off a freeway and stopping at the next light, only to find the converter still locked up, even after shutting the vehicle off and restarting it.

    It takes a whole 30 seconds to eliminate that as a problem entirely, I don't think it woudl be a waste especially if everything visible under the truck has gone through a decent inspection. One of the BEST things that could happen is to find the TCC solenoid is the cause. I don't think its likely, but damn, its easy to test, easy to replace, and a failure prone part.
     

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