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#1
10-16-2015, 07:45 PM
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'01 GMC 2500 HD hard shifts
Been getting hard shifts from my truck lately. Intermittent issue, but may be getting more frequent. If it was in one of my Pontiacs with a TH400, I would say it was the vacuum modulator, but doubt seriously that this truck has one. Replaced by electronics? Tow/haul kicking in randomly maybe?
Fluid level fine, w/ bubbles on the stick when you check it running. Got about 120k on it. What have I got going on?
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"If you do everything you'll win" -LBJ 13 Smiles per Gallon: 66 Bonneville wagon 66 Bonneville 2d HT - In perpetual progress |
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#2
10-18-2015, 05:32 PM
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If you have the 4L80e trans, then check for a knock sensor code. I forget why or how it's tied into the trans wiring but we had that once and it drove us nuts on a dually and only applies to the 4L80 trucks. Had firm applies into drive and reverse. Just general high line pressure
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71 grand prix SJ 4280# 462 new for 2008 - 8.7:1 , 98cc 6Xs 246/209, 342 12bolt , BW S475 turbo JGS 50mm WG 56mm BOV. 600hp the easy way! |
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#3
10-19-2015, 06:50 AM
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Thanks. That makes sense with this vehicle. Had a knock sensor replaced about a year ago. Still have to run premium in it to avoid knocks, but majority of issue resolved. When gas formulas change seasonally I still get the knock even with 93 octane. Also more prone to do the hard shifts when A/C is on.
It's like I got a street strip kit in it!
__________________
"If you do everything you'll win" -LBJ 13 Smiles per Gallon: 66 Bonneville wagon 66 Bonneville 2d HT - In perpetual progress |
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