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Jinxed the 700 by talking about it? Doesn't want to shift right

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Foy, Sep 11, 2003.

  1. Foy

    Foy Registered Member

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    Jinxed the 700 by talking about it? Doesn\'t want to shift right

    Gents- Cooper's dad Foy here. Thanks for all the input on the overdrive ratio. Good advice about the wheel width and max tire tread width, too. We may have jinxed the gearbox talking about it, though. Here's the situation:
    '90 K1500 Sub, 350/700 bone stock, 182,000 miles, trans rebuilt by local (not a "chain) auto tran shop at 159,000 two years ago. Virtually no heavy use or towing since then. Trans did start to "skip" between 2 and 3 on the upshift--meaning the engine would rev just a fraction of a second, after 1 year. Shop took it back in, fixed it under warranty, I never found out what was wrong (my bad). More recently, as posted here, we've gotten some "gear whine", which I thought was the trans case, and a little 1st gear noise. Trans guy says "could be planetaries" but not enough of a situation to justify pulling the trans, says he. Now it's started to act up after a 25-30 mile run. OK for short runs in town (all upshifting and downshifting normal), but after 25-30 mi, in OD, it doesn't drop back in to 1st when you come to a stop. When the shifter is in OD or 3, the gearbox will come back to 2nd at a dead stop, and start in 2nd when you move off. Then it's reluctant to upshift to 3rd from the 3 or OD shifter position. It'll drop to 1st when you pull the shifter down to 1, but then you have to really tach out 1st (25-28mph), let off the gas, and upshift the shifter to 2 in order for her to go into 2nd. When you do that, it goes into 3rd pretty normally, once you tach 2nd out normally and upshift to 3rd manually, and really easily goes on up into lockup and OD. Trans fluid changed 4,000 mi ago, filter too. Fluid level normal, color nice and pink, no burned smell, even tonight after Cooper got back from a 100 mi round trip to training, all highway miles.
    So, are we talking about some vacume and/or onboard computer operated shifting modulation problems here? Trans is not slipping or acting up in any way other than not downshifting to 1st and not easily or properly upshifting to 2nd and 3rd. Any thoughts or ideas I should discuss with my trans guy?

    Oh, and as much as I think 400s and 350s are great, I'm not getting one, so no need to suggest that. I got 159,000 mi out of the OEM 700, with much heavy towing, much of it in OD, before the prior owner and yours truly knew any better, so changing gearboxes is not something I'm interested in. I really like the OD, too.

    Sorry for the long-winded post. Thanks for any help.

    Cooper's dad Foy--financial sponsor of Sub-Culture activities for the Coop.
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    check the TV cable on the throttle bracket. Sounds like something is just out of adjustment because you can manually shift still. The TV cable controls the down shifting and at what rpm it shifts at. I say the shop didn't get it set right when it was put back in. Hope this helps.

    --------------
    85K5 3/4ton, 14boltFF,10bolt, 9"lift,35"boggers,16.5x14 welds, big horse 406SBC/700R-4 /forums/images/graemlins/k5.gif /forums/images/graemlins/angryfire.gif
     
  3. R72K5

    R72K5 Banned

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    yep, TV cable is first thing to look at, to set it you need to manually hold throttle wide open and press in the lockbutton of the TV cable sleeve just behind the throttle cable bracket on intake and take all the slack out of the cable and then release the lock button and go test drive it, if the RPM's dont wind up high enough before shifting then you can pull cable a hair tighter and then test drive again, and also this changes how far down the pedal goes before it kicksdown for passing, you dont want a tranny to be shifting prematurely at klower RPM, this is hard ont he clutch packs, you want a good firm shift but not a crash shift. youll have to fine tune this by adjusting cable and if you cant get it right by cable adjustments then something else is wrong such as in the V/B or the governor

    700r4 are real touchy sometimes, sometimes you just cant get them just right, but with most of them you can., it also dpeendson tire size,IE axle ratio. this changes things, i find that uts easier to get a 700r4 set just right with deeper gears such as 3.42 and 3.7, and not with highway crappy gears such as 2.56, 2.73, etc.


    good luck
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    The test I normally do for a 700 to see if the TV cable is tight is pretty easy. Accelerate slowly until it shifts to 2nd gear at about 10 mph or maybe a little higher. Then mash the throttle and it should immediately downshift to 1st. If it doesn't, your TV cable isn't tight enough.

    Honestly though, if it's shifting fine before you drive 25-30 miles, I think you've got a problem inside. If it shifts fine sometimes and not others, I would say that there most likely is not a TV cable issue.
     
  5. Foy

    Foy Registered Member

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    Foy back here under Coop's login:

    Thanks guys. We'll do some noodling with the TV cable.

    An update from early this morning is that it's not just when it's been run for a while--as of this morning, she won't upshift to 2nd without starting out in 1st, taching her way up, and manually shifting simultaneously letting off the gas. Then she upshifts nearly normally to 3rd, and lockup and OD seem normal. On the down shift side, she'd drop back to 2nd at a dead stop, and would stay up in 3rd on a rolling stop (mebbe 5 mph), so she's acting up after a 9 hour rest from last night. The shifting has been just a tad squirrily since the rebuild, but nothing like this. Plus, this seemed to have come on all of the sudden. Then again, Coop drives the truck every day, and I haven't been behind the wheel but a couple of times in the last 60 days. He's a new driver and may have not noticed odd shifting patterns like I would, with something like a half a million miles in the last 32 years.

    Thanks again. If there are any other comments or ideas, let 'em fly.

    Foy
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    Hopefully it's a TV issue. If it's doing it all the time, that would make sense.
     
  7. Blue85

    Blue85 Troll Premium Member

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    Re: Jinxed the 700 by talking about it? Doesn\'t want to shift right

    Doesn't sound like TV to me, although that should be adjusted before doing other tech on it. Not downshifting to first would not happen at any throttle position at 0mph. Also doesn't sound like the governor because the upper gears come in at normal times and a governor problem is almost always present for every shift. The most common governor problem is a broken gear, which would make it really hard to ever get out of 1st gear.

    The problem always seems to involve 2nd gear, so I would guess that it's either with the 2nd gear band or servo or problems in the valve body with a hanging 1-2 or 2-3 shift valve. The fact that the behaviour keeps changing makes me think there is some junk going through the valvebody.
     

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