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Old 04-29-2010, 09:49 AM   #1 (permalink)
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Default 4EAT - Power Brake Launch Hitting Rev Limiter

I notice that when I power brake/launch that the engine hits the rev limiter before the 4EAT shifts into second gear. I have only "launched" this way once but with a trip to the strip scheduled for tomorrow evening, I'm hoping to get some feedback on the best way to overcome this. If I hammer it from a roll, there is no shifting issues.

My first thought is to launch as described above and as the tach crosses 6k RPM, do a quick off-blip of the throttle and see if that induces the shift.

The other thought is to launch in first and manually shift - though I'm not sure that will solve the problem.

Or, I could just roll out and then nail it, though my ET will no doubt suffer.

If I could get some insight on this before beating on my car any further, it would be appreciated!
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Old 04-29-2010, 12:22 PM   #2 (permalink)
 
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Jim, I have the same issues. The harder the launch, the more it delays on the 1-2 shift. Same results for rolling into it. While I dont think its normal, I will say mine has done the same exact thing.

I have also tried manually shifting it at 5k, with no improved results. My best time of 12.97 could have been down in the 12.8 or even 12.7's with a solid 1-2 shift. I have a trans cooler but im thinking the tcu needs programmed, which their is no programmer for them. So basically, after rambling, yea, mine does the same and I just roll with it(hard outta the hole)
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Old 04-29-2010, 02:33 PM   #3 (permalink)
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Brian, does coming off the gas a touch induce the shift?
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Old 04-29-2010, 04:24 PM   #4 (permalink)
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I've had the same issue multiple times. Even with my built trans. However after my last rebuild by IPT i have not experienced the problem... However i haven't launched it much since the last rebuild...
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Old 04-30-2010, 01:03 PM   #5 (permalink)
 
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Jim, I really cant answer that. Im a hold it to the wood guy and I dont lift(unless their are problems.

My tip for the day.

Bring the following

Note pad.
Tire pressure gauge
Cheapo $10 walmart pressure sprayer(like for stain or bug stuff)

Keep an eye on tire pressure. Record it, also record what your times are and how the car ran and when it shifted after every run.

Use the new clean sprayer to help cool the car between runs, and even sit a bag of ice on the tmic and intake manifold.
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Old 04-30-2010, 02:51 PM   #6 (permalink)
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I have the built IPT Trans and have never hit the rev limiter shifting manually. Only time it has happened was due to driver error. I've never ran the car in either "3" or "D" at the track so I can't say if that makes a difference though.

However I did just do the MultiPlate Transfer Clutch Lock-Up Switch today. I plan to test it at the track soon. Hopefully get my launches down from 2 to 1.7 with it.
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Old 05-07-2010, 05:22 PM   #7 (permalink)
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BTW, the one pass I took down the 1320 with the lame launch the tranny shifted just fine.
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Old 05-07-2010, 06:17 PM   #8 (permalink)
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Did you just leave it in "3" or "D"? Did you catch where it was shifting, was it going up to redline?
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Old 05-07-2010, 08:45 PM   #9 (permalink)
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Quote:
Originally Posted by Canonshooter View Post
Brian, does coming off the gas a touch induce the shift?
Lifting off will get it to upshift. I'd launch in 1st as that will give you full MPT lockup. However, you have to shift quite a bit before you actually want the shift to occur. 1st and 2nd are just too close it seems. I really wish all 4eat equipped FXTs got the VTD center diff, the longer I have the car the more I hate the MPT setup. My mpt seems to be wearing out from all the 2nd gear snow drifting I've done the past few years.
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Old 05-08-2010, 04:58 PM   #10 (permalink)
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Man that 07 6spd is starting to make its way to my car... The more I read the 4eat threads, the more I feel like I am going to blow up any AUTO I get.

Jr
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Old 05-08-2010, 06:47 PM   #11 (permalink)
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Man that 07 6spd is starting to make its way to my car... The more I read the 4eat threads, the more I feel like I am going to blow up any AUTO I get.

Jr
imo the stock auto is stronger than the stock 5mt if you don't overheat it or split the front diff casing. If all FXT's came with the VTD, I'd take it over any of the manual offerings, but the MPT just ruins it for performance driving. I wish they had DCCD for the auto!
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Old 05-08-2010, 10:30 PM   #12 (permalink)
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Man that 07 6spd is starting to make its way to my car... The more I read the 4eat threads, the more I feel like I am going to blow up any AUTO I get.

Jr
Go for the gold and put a built LGT 5EAT w/sportshift in. I think you may also be able to get a front LSD for it too
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Old 05-09-2010, 02:18 PM   #13 (permalink)
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Go for the gold and put a built LGT 5EAT w/sportshift in. I think you may also be able to get a front LSD for it too
Point me in the right direction. I just blew the stocker up.. Figures!
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Old 05-09-2010, 02:26 PM   #14 (permalink)
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Did you just leave it in "3" or "D"? Did you catch where it was shifting, was it going up to redline?
Left it in "3" the entire time. Didn't watch the tach but seemed to shift at the usual points.

FWIW, I very rarely get more than just a very short squeal from the front tires. It seems to transfer to the rear wheels very quickly.
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Old 05-09-2010, 02:28 PM   #15 (permalink)
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I'm thinking it's due to the higher horsepower you guys are running. I've launched mine a few times, and it just goes to redline and shifts fine. You guys are running a lot of extra power, and running throughout the RPM range at a much higher rate of speed than stock. I'm thinking this could possibly be, in a word, "confusing" the system a bit as it gets to redline a hell of a lot faster than stock would. This, of course, is just a guess, but it seems that everyone having the issue all have high-horsepower modifications. Just a thought.
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