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Transmission Trouble

swanthog

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swanthog Enthusiast

swanthog

Posted
Posted

Hi all.

 

I just picked up a '77 Silverado 10, 350, full-time 4x4, auto transmission. I drove it home loaded with a HUGE and heavy camper. The truck did great even up steep grades. The next day I removed the camper and now I have no forward gears. I checked the tranny fluid. It took three quarts to return to normal operating range. Still no forward gears.

 

My first question is, what happened to my tranny? Did I burn it up running it with low fluid?

 

Next question, if I need to replace the tranny, what years of GM's would be a direct replacement? I'm guessing that the tranny is a turbo 350.

 

Thanks!

Import Hater Enthusiast

Import Hater

Posted
Posted
My first question is, what happened to my tranny? Did I burn it up running it with low fluid?

 

Next question, if I need to replace the tranny, what years of GM's would be a direct replacement? I'm guessing that the tranny is a turbo 350.

 

Thanks!

Yeah, you probably killed it. You may have the TH400, but I don't think so. Most likely the TH350. If you're going to replace it, you might want to try and get a 700R4/4L60 instead. It's just a better tranny overall. You'll see some better mileage out of that beast with that too.

 

Rob

willick Enthusiast

willick

Posted
Posted

Your best bet would be to use a 700R4, they are basically a TH350 with overdrive, but get a 1987 or newer one because before that they had a terrible reputation for being unreliable.

 

If you want a heavy duty tranny I would get a 4L80E, these are basically a TH400 with overdrive, only problem is they are computer controlled so being an older truck you would need to pick up an aftermarket computer which is big $$

 

cheers!

cgabe Enthusiast

cgabe

Posted
Posted

Your truck made it home just fine , drove up on the driveway just fine, went to sleep overnight , and next day lost the forward gears? It's kinda hard to believe...

No symptomes the day before? Hmm...

Check your tranny linkage or better yet see if you can engage the tranny by hand (the little lever on the tranny, oh, and make sure you have someone pressing the brake pedal, or block the wheels, or ... you know ... don't let the truck rol over you while under it) =)

 

gabe

swanthog Enthusiast

swanthog

Posted
  • Author
Posted

Gabe,

 

I know it seems strange. I coudn't really believe it myself. Here's a possible explanation from someone on another forum:

 

>You very well may have burned out the clutch plates. Once they cool down and >settle back into place, they may not grip again. Usually you have other >symptoms first, like a delay getting into gear after you shift, but if the bands >wear out that could do it. Another possibility is that something in the valve body >is stuck because of the heat. It's really hard to say without tearing it apart.

 

Make sense to anyone?

 

--Larry

cgabe Enthusiast

cgabe

Posted
Posted

Yes , it does make sence, and if that is so , what I would do is experiment with the tranny. You would have to take the tranny out anyways so look into a rebuilt kit for it. A auto tranny is pretty simple to rebuilt especially a TH350. All you have to keep in mind is the way you take the old clutch plates out that's the way the new ones go in (in exact same order)

A good candidate for a swap would be a 700R4 'cause it has a OD but you got to keep in mind the t-case adaptor plate to the new tranny, the linkage to the shifter, and now the driveshafts will have diffrent lengths.

So to keep things really simple I would stay w/ the TH350. They are bomb proof with proper maintainence. Sorry I couldn't be more help :(

  • 1 month later...
C1500 Enthusiast

C1500

Posted
Posted

Keep the TH350/400 tranny. with the full-time 4wd you probably have the NP203 transfercase, and there probably isn't an adapter to fit that to the later model trannys. so you would have to replace that too, & then you would have to replace the hubs to make it part-time 4wd.

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