Turbo 350 (TH350) Information Thread

[AuroraGirl]

Well yes, that is certainly possibly too. It could have been bound up and caused the rear planets to explode. Nonetheless, there was a catastrphic failure somewhere in the back of the case behind the center support.

Someone blew up its behind

Stay frosty and watch your 6

Lol. But interesting. Im hoping the np203 is ok, but i suspect the failure started there because of things it did before it died. I am not worried too much but if it is a loss, darn

I still have one on my 78 lol

 

[Old Blu]

Hello all I have a 77 k20 turbo 350 that's giving me fits. It blows the dipstick up out of the tube about 1-2 inches after driving it even a little distance to town and back about 15 miles. Just running in shop never an issue. I just changed fluid and filter thinking that might be a problem as well as trying to clean the vent on the left side above shifter. Any ideas?

Hello 77 K20,
I am having the same problem with my TH350. Almost had a fire under the hood when the fluid hit the headers! I pulled out the vent and now the fluid just goes out there. I have to top off the Tranny often and the bottom of the trans pan is starting to rust. The fluid has removed all the paint.
I would love to hear from some experts on this as well.
Cheers,
Old Blu

 

[BRetty]

@NickTransmissions I realized I had not thanked you for all your info here and videos on YouTube. My th350c was rebuilt 1.5 years ago and is going strong, but I feel way more prepared when she needs some more attention.

Maybe one day I will even hook up my lockup conveter clutch.

 

[HotRodPC]

@NickTransmissions I realized I had not thanked you for all your info here and videos on YouTube. My th350c was rebuilt 1.5 years ago and is going strong, but I feel way more prepared when she needs some more attention.

Maybe one day I will even hook up my lockup conveter clutch.

I don't know if it'll work since the post was already submitted and I just edited it, @BRetty , but I put the @ symbol in front of Nick's name so he'll be tagged and better chance of seeing your post. So now in the future, you're aware how to use that feature.

I sure would hook up that Lock Up Converter Clutch. I mean, if you have it, use it. The 200-300 rpm difference just might save you a bit of gas and for damn sure will help your transmission run cooler on freeway rides which in turn makes your transmission last much longer. Heat is the #1 killer of auto transmissions and also keeps your fluid cleaner longer so maintenance intervals can be stretched out a bit further. Even if you hooked up it manually, it's better than nothing. Have a push button to turn it on after you reach your cruising speed then hook a wire to your brake light switch to cancel it. Best to hook it up right though cuz you don't really want it locked up when you do things like step down on the skinny pedal and downshift to 2nd. But yeah, I'd get it hooked up ASAP and take advantage of the benefits of it, mainly a cooler running transmission and less clutch wear which dirties up your fluid.

 

[carterjdrake]

Hi there!

I have an 85 k10 with a recently purchased th350 transmission, supposedly low mileage. Just got it installed and the fluid topped off. Cycled it through all the gears about 15 times. When shifted into gear I can feel it engage (truck tries to lurch) then immediately feels like it's been shifted into neutral. Same thing happens in forward or reverse. Is this a sign of a bad pump or something else?

It's got an np203 behind it. Thanks.

 

[AuroraGirl]

Hi there!

I have an 85 k10 with a recently purchased th350 transmission, supposedly low mileage. Just got it installed and the fluid topped off. Cycled it through all the gears about 15 times. When shifted into gear I can feel it engage (truck tries to lurch) then immediately feels like it's been shifted into neutral. Same thing happens in forward or reverse. Is this a sign of a bad pump or something else?

It's got an np203 behind it. Thanks.

Sounds like the lurch you feel is the fluid operating and the drag , I feel like your transfer case is a good suspect. The put in while off in high or low lok
Restart, try gears with Foot on brake

 

[BRetty]

I don't know if it'll work since the post was already submitted and I just edited it, @BRetty , but I put the @ symbol in front of Nick's name so he'll be tagged and better chance of seeing your post. So now in the future, you're aware how to use that feature.

I sure would hook up that Lock Up Converter Clutch. I mean, if you have it, use it. The 200-300 rpm difference just might save you a bit of gas and for damn sure will help your transmission run cooler on freeway rides which in turn makes your transmission last much longer. Heat is the #1 killer of auto transmissions and also keeps your fluid cleaner longer so maintenance intervals can be stretched out a bit further. Even if you hooked up it manually, it's better than nothing. Have a push button to turn it on after you reach your cruising speed then hook a wire to your brake light switch to cancel it. Best to hook it up right though cuz you don't really want it locked up when you do things like step down on the skinny pedal and downshift to 2nd. But yeah, I'd get it hooked up ASAP and take advantage of the benefits of it, mainly a cooler running transmission and less clutch wear which dirties up your fluid.

Thanks for the prod to do something I should have done a long time ago. I'm pretty sure I have the vacuum switch and assorted tubing, the connectors at the pigtail and the housing are pretty degraded tho, and there was a lot of unconnected wires from when the PO swapped in the engine and trans from an '81 Suburban. In particular, I need to figure out if the socket on the right (pass) side of the tranny, which I think is just a "is there trans fluid pressure aka are we really moving?" switch, really needs to be in the circuit.

But mostly I'm just stalling, excuses like "no garage to work on it", no money (tho I have all the parts), and "maybe when I do this I have the trans shop test it first in case something blows up". And BS like, "While I'm doing this I should swap my quadrajet for the Edelbrock I have sitting in a box, and, my vacuum canister also in the box, and, and...." that BS. I'm not working, so not making the 40-mi daily highway r/t, but I hope that changes and then I will need it and have no time then. So do it now!

Thanks