Trans rebuilt, now higher RPM??? - TCCoA Forums
 
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post #1 of 12 (permalink) Old 08-17-2006, 09:56 AM Thread Starter
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Trans rebuilt, now higher RPM???

Ok, I'm asking this question about my brother's 95 Bird. 2 years ago he bought a 95 4.6 with ~120k miles. It was in excellent running condition except for a weird trans problem. It would shift erratically and when cruising on the highway would randomly downshift or go into neutral. In hopes of solving the problem, he got the trans rebuilt, but the problem still existed. Anyway, time goes on, diagnostics happen, and as you all have probably already guessed by now, it was the MLPS.

So before the rebuild, at 75 mph his RPMs were ~2200. Immediately after the rebuild, his RPMs were ~2400 at 75 mph. What gives? He had the VSS replaced but no change. The speedo gear is the same as before the swap. Rear end hasn't been changed. He had the actual speedo head in a shop and they checked it and it tested fine. Anyone have any ideas as to why this would happen right after the rebuild? Thanks in advance.

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post #2 of 12 (permalink) Old 08-17-2006, 10:17 AM
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TC is never locking?

Cruise along at 75 mph and watch the tach (and the road). press the brake just enough to light up the tail lights, and see if they RPMs go up. If they do, then the TC is locked (putting on the brake makes it unlock). If it doesn't change, then the TC isn't locking.

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post #3 of 12 (permalink) Old 08-17-2006, 10:22 AM
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Quote:
Originally Posted by Bangster
TC is never locking?

Cruise along at 75 mph and watch the tach (and the road). press the brake just enough to light up the tail lights, and see if they RPMs go up. If they do, then the TC is locked (putting on the brake makes it unlock). If it doesn't change, then the TC isn't locking.
Been there done that and had the exact same symptom.

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post #4 of 12 (permalink) Old 08-17-2006, 11:55 AM Thread Starter
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TC is locked.

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post #5 of 12 (permalink) Old 08-17-2006, 12:12 PM
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Then I have to question if the overdrive band is holding properly.
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post #6 of 12 (permalink) Old 08-17-2006, 01:22 PM Thread Starter
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Quote:
Originally Posted by dirtyd0g
Then I have to question if the overdrive band is holding properly.
Alan
How does one find out such a thing? Is tranny disassembly necessary?

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post #7 of 12 (permalink) Old 08-17-2006, 02:18 PM
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I'm sure you could log it with an ngs or snap on scanner. If it were here I'd take the trans out and have a look at the band.
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post #8 of 12 (permalink) Old 08-17-2006, 02:24 PM Thread Starter
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Ok thanks Alan. My brother theorizes that the people who rebuilt his trans may have installed the OD parts from an AODE. Two questions.

1) Is this even possible? Will parts from an AODE fit and could this cause this anomaly?
2) If the above is possible, wouldn't the AODE's 0.67 OD ratio drop the RPM's instead of raising them?

Thanks again.

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post #9 of 12 (permalink) Old 08-17-2006, 04:03 PM
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If they installed an aode ratio thats your problem. The computer likely doesn't understand what is going on.
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post #10 of 12 (permalink) Old 08-17-2006, 04:07 PM
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Could it not be the wrong(different) output shaft? I.E., the speedo is not the same?
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post #11 of 12 (permalink) Old 08-17-2006, 04:14 PM Thread Starter
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So it IS possible to install an AODE OD ratio? Ok, say that they did that. Does anyone know the calculations to see what RPM difference that 0.03 difference would make and whether it would raise or lower the RPMs?

And is it possible to have the wrong output shaft on there? would it fit in the trans and still be able to fit the driveshaft?

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post #12 of 12 (permalink) Old 08-17-2006, 08:17 PM
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Quote:
Originally Posted by master486
And is it possible to have the wrong output shaft on there? would it fit in the trans and still be able to fit the driveshaft?
I believe there are 7 and 8 tooth drive gears on available output shafts, I've heard of this dilemma before.

You can play with this calculator.
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