Is there anything else b4 I start pricing new trannys? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-12-2006, 06:57 AM   #1
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Default Is there anything else b4 I start pricing new trannys?

I have a problem w/the tranny on my 88 sse not shifting into OD until reeellly high rpms(4000 to 5000). I have installed tranny cooler, tranny has fluid and does not leak, adjusted TV cable. The only thing left I know to try is replace and not adjust the TV cable. Any ideas? Also is the TV cable the same as the shift linkage cable?
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Old 08-12-2006, 08:08 AM   #2
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Default Re: Is there anything else b4 I start pricing new trannys?

Quote:
Originally Posted by spidey3479
Also is the TV cable the same as the shift linkage cable?
Negative. TV (Throttle Valve) just runs from the throttle body down to the throttle valve in the valve body of the transmission. The shift linkage cable runs from your column/floor shifter to the transmission.

Upshifts are all controlled by the TV, governor, and modulator. Based on what you said, I presume you are getting a high rpm upshift in light to part throttle operation (because if you are hammering the throttle W.O.T, then you want high rpm upshifts)

Check your vac line to the modulator (Little can on the front side of the transmission case..mine says "Holley" on it.) It modulates transmission line pressure opposite vac...so if it is leaking, you get hard/delayed upshifts (0 vac to modulator = max line pressure inside the transmission)

If you have adjusted the TV right (backed the cable all the way out, then pushed the accelerator pedal all the way down) there really isn't much left on the outside of the transmission. Everything else would be in the valve body.
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Old 08-12-2006, 01:13 PM   #3
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I have replaced the modulator with the adjustable kind, would an adjustment do the trick?
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Old 08-12-2006, 03:57 PM   #4
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Quote:
Originally Posted by spidey3479
I have replaced the modulator with the adjustable kind, would an adjustment do the trick?
Could very well be the case. These modulators are kinda new to me. Most of my experience has been with the THM700R4 (4L60) which doesn't have a vac operated modulator.

If I understand these things correctly, line pressure starts with input shaft RPM driving the pump, and the vac modulator dumps the excess pressure. So, anytime the throttle is not at WOT, the modulator is dropping the line pressure and softening up the shift points. The governor still decides when it'* time to change gears based on output shaft speed, but it needs line pressure to shuffle the valves, apply/release the clutches, and make the shift happen. If it ain't there, then the shift is delayed.

Just for grins and giggles, try jumpering the modulator vac to someplace with a good vac supply all the time (like the vac resevoir side of the check valve) That should pull a constant vac on the modulator. Now take it for a spin and see if you get soft shifts in all gears.
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Old 08-12-2006, 04:53 PM   #5
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On the 440-T4(4T60) and the 4T60-E the Vac modulator has more control on shift quality than anything, On the 440-T4 I will have to agree tho that in part does have a little to do with the shift timming.. I may have to test this out later... If the TV cable is a little out of adjust ment it would be possible to have a delayed shift... 4000 rpms almost makes me thing the cable is either pulled all the way back( past its self adjusting point ) or there is an issues with the Valve body as stated...

Like curt has stated if you do not find or can't correct the problem Via the Modulator of the TV cable, it may be time to suspect the trans

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Old 08-13-2006, 03:10 PM   #6
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I finally got a chance to adjust and road test the tv cable and vac mod valve that I installed. The shifts are a little soft but the OD kicks in fine. She does 60 at about 2500 to 3000 rpms, but still will rev to 4000 for 3-5 secs b4 shifting to OD. Guess I'll have to live with that until I get the oem tranny rebuilt. I thought that the TV cable was supposed to be pulled out as far as possible for adjustment. This is what I read in the repair manual.
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Old 08-14-2006, 06:29 AM   #7
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Moved the TV cable in the other direction and all shifts moved down on rpms, even OD. Still sticks for a couple of seconds sometimes before that last shift into OD. So again, anybody got suggestions or related articles or posts on a performance rebuild? What should I have them do?
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