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Old 05-11-2015, 07:24 PM   #1
 
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Default Hitting the limiter in the TA. Why?

So a week or so ago I swapped the built 4l60 into the TA. A clip in a solenoid broke and burnt up a few bands. Had it rebuilt. In the meanwhile I ran the stock Trans and had no problems with it. Finally my buddy finished up the rebuild so we put it back in. I test drove it and seemed to shift fine, made a pass and did a wot 40 roll all shifts seemed fine. Fast forward to a yesterday. Finally got the new rims and tires on, take it for a test drive and now it hits the limiter on the 2-3 shift. Would putting a taller tire on it 26 to 28" make it hit the limiter? I would think that would only happen the other way around. I'm thinking the Trans is just junk and is burnt up already and I need to ditch it for an 80 and put the stock one back in for now. Any thoughts?
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Old 05-11-2015, 07:40 PM   #2
 
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I don't think changing a wheel and tire would make an auto trans shift at a different rpm .
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Old 05-11-2015, 07:57 PM   #3
 
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Default Hitting the limiter in the TA. Why?

It changes your rotational speed. From what you are going vs what the car thinks. Also from the start a shop that I won't name, which is not around anymore did not have his speedo set correctly from the get go. Last time we cruised he said he was going like 70 and mine said 60-65. And I know mine is right. And that was before his tire swap

My vote like I told you in a text is the Trans shift points and possible gear ratio. With what the car thinks it has.
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Old 05-11-2015, 08:40 PM   #4
 
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I just doubt the shift point thing because the only reason for hitting a limiter is going higher rpm before shifting. If it shifts at a certain speed it's gonna hit that speed at a lower rpm with a taller tire and shift at a lower rpm than before.
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Old 05-11-2015, 08:56 PM   #5
 
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Well idk why it was fine before and now the only thing we know for sure is you changed tire height and now it's all funky.
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Old 05-11-2015, 08:58 PM   #6
 
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Or the Trans is shit and took a shit already
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Old 05-11-2015, 08:58 PM   #7
 
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Unless the stock Trans is letting go and is slipping in the higher rpm range making it think that it is redlining
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Old 05-11-2015, 10:48 PM   #8
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put the stock tires on real quick and see if it still hits the limiter.

process of elimination.
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Old 05-11-2015, 11:13 PM   #9
 
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It should be the tire change. Full throttle shift points in the Fbody PCM's are decided by MPH and RPM. It needs to satisfy both criteria to shift, and they have to occur in a pretty close timeframe (forget what it is). If you changed the tire size and didn't modify the tune, it will absolutely affect this.
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Old 05-11-2015, 11:19 PM   #10
 
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Why would it only be going from 2nd to 3rd then ?
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Old 05-11-2015, 11:28 PM   #11
 
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It could be his original tune happens to satisfy both criteria within an acceptable period and shifts during that particular shift. I can't say for certain without looking at the tune and a log. If the OP uploads an hptuners log and his tune, it will be easy to see if that's his problem.

The tune should have an RPM and a MPH that need to be satisfied for each shift. If one one parameter is met, and the other takes too long the car will not shift. If you bolt a 28" tire on a stock car, it will not work correctly unless the speedo is adjusted.

Put the original tires back on and that will rule this out.
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Old 05-11-2015, 11:32 PM   #12
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Quote:
Originally Posted by P40E View Post
I don't think changing a wheel and tire would make an auto trans shift at a different rpm .


Many auto transmissions command shifts based upon engine RPM AND vehicle speed. So changing tire size without modifying the tune to compensate can screw the shifting up.


EDIT: Nevermind, DNKStang already mentioned what I said. Yep, the issue is pretty much guaranteed to rest with your tune needing re-adjustment so don't fret about a blown trans just yet.
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Old 05-12-2015, 08:23 AM   #13
 
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Guess I'll swap the other tires on real quick and see if it does this. Wish I had hptuners and a way to log runs
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Old 05-12-2015, 08:26 AM   #14
 
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Guess I'll swap the other tires on real quick and see if it does this. Wish u had hptuners and a way to log runs
If it doesnt do it then good. However that still leaves you needing a tune. Well at least small shift point adjustments. And I believe speed inc is quite backed up. Def would not happen by this Friday, and I dont think that would matter anyway as the rain is still in the forcast all day for the track.
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Old 05-12-2015, 09:20 AM   #15
 
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I know it's different cars but I second all the stuff about tire height, I change the revolutions per mile in the tune every time I switch to my track tires on my mustang or it will hit the limiter
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Old 05-12-2015, 09:55 AM   #16
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Your shift points will change because of the tire size. You need to adjust the tune a cunt hair.
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Old 05-12-2015, 01:09 PM   #17
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With a taller tire you're going to drop the engine RPM for a set speed. Shouldn't cause issues with the limiter IMO.

On the other hand, let me guess you're going from a stockish converter to an aftermarket style one? Just a shot in the dark.
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Old 05-12-2015, 01:52 PM   #18
 
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I've had the same 3800 lock up converter in the car for a few years now
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Old 05-12-2015, 02:29 PM   #19
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Interesting usually it's excessive slipping that causes issues like that. Do your RPMs under load seem higher than they were before? Also if you use say 1-2 manual vs 3 manual vs 4 manual do you notice any differences?
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Old 05-13-2015, 12:03 AM   #20
 
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Put the stock Trans back in today. Works like a charm
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