ledfoot Posted February 18, 2008 Report Share Posted February 18, 2008 I have read Zippy's excellent transmission explanation on the website and have a few questions as it pertains to a recent problem that has developed with my 2005 2wd Silverado SS. First, I am the original owner of the truck, and it has only 10,500 miles on it. The only mods are a cat back Magnaflow and a "PCM's for less" reflashed pcm. I have not installed billet servos or any other trans mods. The PCM definitely gave it some harder shifts, and has been in the truck since it had about 1000 miles on it. My problem: the other day the trans held 1st gear a little longer than normal. An isolated incident that has not occurred since. But, it got me thinking and a little worried because I am about to tow an enclosed trailer hauling a Chevelle from CA to FL, I was supposed to leave in 2 days!. I picked up the trailer, drove about 90 miles with it (empty), and everything seemed fine. The next day, on the freeway and in cruise control at about 78mph, my lockup in overdrive started "hunting" back & forth between 2300rpms & 3000. If I put it in 3rd gear it held fine. No other symptoms were noticed. I got where I was going and shut the truck down for a half hour, started it back up and it hasn't happened since. I'm going to reinstall my original PCM (I kept it), and see what happens. The truck is still under warranty. Can you please offer any explanation of what is wrong, and how to handle this before I go on my trip? Can I "persuade" the dealer drop the pan if they can't duplicate the problem? Thanks in advance, Jeff cell: 626-808-8101 Quote Link to comment Share on other sites More sharing options...
desrtrat Posted February 18, 2008 Report Share Posted February 18, 2008 on the freeway and in cruise control at about 78mph, my lockup in overdrive started "hunting" back & forth between 2300rpms & 3000. If I put it in 3rd gear it held fine. i would say that is your problem. in OD it can't make up it's mind, locked will pull for a short distance, then decides it needs to down shift. i think your trans will be all right for a while, but towing that kink of weight, and at that speed, IMO.. is asking for a disaster to happen. trying to stop fast, GM brakes are not the best even with trailer brakes it will be a tough. most ST225-75R-15 tires are ONLY speed rated at 65 mph max... Quote Link to comment Share on other sites More sharing options...
ledfoot Posted February 18, 2008 Author Report Share Posted February 18, 2008 Thanks for the response, and sorry for the confusion. The problem happened the day AFTER I towed the trailer. The day before when I towed the trailer empty @3500lbs, the trans seemed ok. I tow between 60-65mph BTW. on the freeway and in cruise control at about 78mph, my lockup in overdrive started "hunting" back & forth between 2300rpms & 3000. If I put it in 3rd gear it held fine. i would say that is your problem. in OD it can't make up it's mind, locked will pull for a short distance, then decides it needs to down shift. i think your trans will be all right for a while, but towing that kink of weight, and at that speed, IMO.. is asking for a disaster to happen. trying to stop fast, GM brakes are not the best even with trailer brakes it will be a tough. most ST225-75R-15 tires are ONLY speed rated at 65 mph max... Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted February 18, 2008 Report Share Posted February 18, 2008 (edited) You should start by checking your fluid level, being off by as little as 1 quart can cause shifting problems. I hate to say it, but those can be the beginning symptoms of future transmission problems. There is the possibility of a cracked accumulator piston based on your symptoms. Towing a trailer as far and as heavy as yours there are a few modifications you should consider............ Shift Kit Vette Servos Alluminum Accumulator Pistons Larger trans cooler Bigger brakes As already mentioned, the stock AWD 4-wheel disc brakes aren't the best, and you will see that first hand towing. Also, towing that kind of load will get the trans very hot especially at highway speeds, so a bigger trans cooler is a good bet to keep temps down. High transmission temps contribute to most trans failures. A shift kit will firm up the shifts and also help prolong transmission life. Edited February 18, 2008 by Fireman31 (see edit history) Quote Link to comment Share on other sites More sharing options...
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