Who knows auto tranny's? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Storm Chaser · 02-07-2009, 11:56 PM

Well, I finally got the engine timed and running smoothly, so I decided to take it for a spin to see if the transmission that came with the truck was going to work out. After spending forever to find a crack in the vacuum line, I finally got it to shift correctly.

But here's the deal- when in is in first, you can hear a rattle that kinda sounds like a lifter rattle, only it is coming from the tranny. The rattle increases with speed, and right before it shifts into second, the rattle gets real quick. The rattle quits about a half second before you feel it go into second. After that, there is no more rattle and all seems well... until you come to a stop and the tranny has to start in first again. It happens EVERY time and only in first.

It doesn't seem to be affecting the operation of the vehicle, but I know this isn't right. I don't want to have a full load in the back and have the tranny go out in a bad part of town or something. Can anyone tell me what's going on? Is it easily fixable, or is it internal (ie junk)?

sierra4x4 · 02-08-2009, 10:28 AM

What tranny do you have, is it a Th350 or Th400?

Storm Chaser · 02-08-2009, 02:06 PM

Th350

James McClure · 02-08-2009, 03:47 PM

Storm, drive it and shift it manually. Start in 1 and pay attention to the noise, next bump it up to 2. how much does the noise change? Is it totally gone or just mostly gone? There are 2 planetary gear sets in there. Ist uses both, 2nd uses 1 and 3rd uses none. If noise is gone in 2nd and 3rd the gear set is gone and unit needs rebuild. Take the pan off and you will probably see a good amount of metal, if ya do, get another unit. jim

Storm Chaser · 02-08-2009, 05:57 PM

Thanks for the response. As far as I can tell, the noise is absent in 2nd and 3rd. Luckily, I have another transmission I can stick in it.

I bought this truck off of Ebay- the ad stated that the engine was bad. After talking to the guy, he said he didn't know if the tranny was good or not because the engine ran so poorly he couldn't check it. The engine I took out was a 267 V8 wearing one 350 head and an evil rod knock. As I said, the tranny is a th350. According to the RPO sheet that does match the VIN, the truck was supposed to have a 350 4bbl with a turbo 400. The emissions sticker is from a different truck that had a 305.

So yea, it's been pieced together... Almost like someone put it back together with their bad parts after robbing it of the good ones. Oh well, a tranny change and an idler arm and she'll be hauling my junk/firewood/building materials.

02-07-2009, 11:56 PM	#1
Storm Chaser Registered User Join Date: Oct 2006 Location: In the Indiana Corn Posts: 449	Who knows auto tranny's? Well, I finally got the engine timed and running smoothly, so I decided to take it for a spin to see if the transmission that came with the truck was going to work out. After spending forever to find a crack in the vacuum line, I finally got it to shift correctly. But here's the deal- when in is in first, you can hear a rattle that kinda sounds like a lifter rattle, only it is coming from the tranny. The rattle increases with speed, and right before it shifts into second, the rattle gets real quick. The rattle quits about a half second before you feel it go into second. After that, there is no more rattle and all seems well... until you come to a stop and the tranny has to start in first again. It happens EVERY time and only in first. It doesn't seem to be affecting the operation of the vehicle, but I know this isn't right. I don't want to have a full load in the back and have the tranny go out in a bad part of town or something. Can anyone tell me what's going on? Is it easily fixable, or is it internal (ie junk)? __________________ 1988 R2500 Crew Cab Immediate plans- get it running! Future plans- Rear disc swap & Hydroboost Dually conversion with shackle flip-n-switch 4x4 conversion with 52" springs Maybe some new body panels Who needs a car when they make crew cab trucks?

02-08-2009, 10:28 AM	#2
sierra4x4 Registered User Join Date: Jan 2009 Location: Canada Posts: 308	Re: Who knows auto tranny's? What tranny do you have, is it a Th350 or Th400?

02-08-2009, 02:06 PM	#3
Storm Chaser Registered User Join Date: Oct 2006 Location: In the Indiana Corn Posts: 449	Re: Who knows auto tranny's? Th350 __________________ 1988 R2500 Crew Cab Immediate plans- get it running! Future plans- Rear disc swap & Hydroboost Dually conversion with shackle flip-n-switch 4x4 conversion with 52" springs Maybe some new body panels Who needs a car when they make crew cab trucks?

02-08-2009, 03:47 PM	#4
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Who knows auto tranny's? Storm, drive it and shift it manually. Start in 1 and pay attention to the noise, next bump it up to 2. how much does the noise change? Is it totally gone or just mostly gone? There are 2 planetary gear sets in there. Ist uses both, 2nd uses 1 and 3rd uses none. If noise is gone in 2nd and 3rd the gear set is gone and unit needs rebuild. Take the pan off and you will probably see a good amount of metal, if ya do, get another unit. jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

02-08-2009, 05:57 PM	#5
Storm Chaser Registered User Join Date: Oct 2006 Location: In the Indiana Corn Posts: 449	Re: Who knows auto tranny's? Thanks for the response. As far as I can tell, the noise is absent in 2nd and 3rd. Luckily, I have another transmission I can stick in it. I bought this truck off of Ebay- the ad stated that the engine was bad. After talking to the guy, he said he didn't know if the tranny was good or not because the engine ran so poorly he couldn't check it. The engine I took out was a 267 V8 wearing one 350 head and an evil rod knock. As I said, the tranny is a th350. According to the RPO sheet that does match the VIN, the truck was supposed to have a 350 4bbl with a turbo 400. The emissions sticker is from a different truck that had a 305. So yea, it's been pieced together... Almost like someone put it back together with their bad parts after robbing it of the good ones. Oh well, a tranny change and an idler arm and she'll be hauling my junk/firewood/building materials. __________________ 1988 R2500 Crew Cab Immediate plans- get it running! Future plans- Rear disc swap & Hydroboost Dually conversion with shackle flip-n-switch 4x4 conversion with 52" springs Maybe some new body panels Who needs a car when they make crew cab trucks?



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