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Old 08-24-2016, 01:08 PM   #1
Matt 4.3 TBI
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Location: TX
Posts: 276
Odd 2-1 issue

I had a new 4L60E built about six months ago and it failed within two weeks (TCC would not unlock, then bands started slipping after TC was replaced). The shop I used gave me a two year warranty so they put in another new unit. This one has been exhibiting some odd behavior and I've had it back at the shop twice now and they've been unable to satisfactorily explain or correct the issues.

First - a rattling/groaning noise coming from the trans when cold. They heard the sound but insisted it was my power steering pump. The sound does not change pitch in neutral with engine rpm or when turning the wheel. I hear the PS pump groan, though. The noise changes pitch when I put the trans in gear and when I accelerate in gear. Noise is only present when it's cold, it's quiet once it comes up to operating temp.

Second - feels like it starts in 2nd when in the D position. This happens mainly when the trans is warm. If I stay light on the throttle it does not shift until about 21mph (into 3rd). If I push on the gas as normal there's about a second delay then you feel a thump likes harsh shift and it starts rolling in first, shifts normally until you come to a stop again. It starts in 1 with the shift lever in 1. If I come to a stop and let off the brake it won't roll forward unless I pull it down to 1. However, if I come to a stop and powerbrake it up to 1000rpm it will start in 1st every time. The shop owner states he as driven the truck for an hour each time I brought it back and has not experienced this.

Lastly - tachometer fluctuates about +/- 300 rpm just after TCC engages. Can feel it noticeably surging. More noticeable at lower speeds, 41-45 MPH. Fluctuates only about 100 rpm in the 60-70 range. Shop owner states scanner shows the TCC remains locked and he thinks it may be the TPS sensor.

If anyone has any feedback I'm open to anything. I really don't want to pay a second shop to diagnose this but I'm getting quite frustrated and I have too much cash tied up in this trans to just ignore it.
00 Blazer ZR2 LS 4WD 4.3L
91 S-10 Blazer Sport 4WD 4.3L
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Old 08-24-2016, 01:20 PM   #2
Matt 4.3 TBI
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Join Date: Jan 2003
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Posts: 276
Forgot to add when shifting into reverse, the truck doesn't roll when I release the brakes until I give it some gas and then I feel a thump like it shifts.
00 Blazer ZR2 LS 4WD 4.3L
91 S-10 Blazer Sport 4WD 4.3L
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Old 08-25-2016, 08:06 AM   #3
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I've been through the transmissions several times and know the basics about them, but man, it'd be hard to try and trouble shoot those types of problems over the net.

About the only thing I can offer is ask the shop to put a pressure gauge on the trans when they're testing it AND RIDE WITH THEM, purchase a pressure gauge and do it yourself, or pay a 2nd shop to do it.

This is purely over the internet advice, take it with a grain of salt. You hear a noise when cold and it sounds like you're having pressure problems. I'd lean towards the pump in your trans is bad. They might have screwed it up when the installed the new tc and didn't have it seated before reinstalling the trans. Right now the guy probably isn't making any money on your truck and isn't trying to help.
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