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-   -   Turbo 350 Trans Shift/Slip issues (http://www.hotrodders.com/forum/turbo-350-trans-shift-slip-issues-165874.html)

CincyMuscle 09-29-2009 07:41 AM

Turbo 350 Trans Shift/Slip issues
 
Hi, I'm new here and will hopefully stick around if this deal on a 70 Monte Carlo goes through. That being said, I wen't to drive the car in question 350 engine and 350 trans and what I had happening was this:

The owner said the car was once an automatic converted to manual shift via a solenoid that selects the gears so I would go from L1 to L2 to D as you would from 1st 2nd to 3rd.

So I head out for a test drive and it starts not shifting into a lower gear when I go to L2. I learn this is because my revs aren't high enough so I correct that and it shifts OKAY. I say it like that because almost every time I shifted into 2nd(L2) it would jerk very hard chirp the tires and 3rd(D) would as well just no tire chirping. Well as I start driving on the highway everything is going good until I give it more than a half throttle and it starts spitting smoke/backfiring when I let off the gas. Then it just cuts out on me all and all and I have to wait for the owner to come with a new battery because apparently the alt was shot. So after we get the new battery I start following him home.

On the way home I notice if I give it more than half gas in 3rd(D) it shifts into a higher gear and gets stuck there until I shift down into 2nd(L2) and then back into third. Which is annoying because I have to slow down to about 30 to shift back into 2nd without im sure locking up the rear wheels.
Anyways I like the car and the engine runs strong as ever minus the smoke and the backfire which I'm not sure can happen because of a bad battery but was gone after the new one was put in. So I would like to know what this could possibly be given the description. I know the description was not perfect and I know relatively little about these Chevy's since I normally have Mopars(please don't shoot me). So I thought I would ask some of you as you would know better than I. Thank you for your time.

SSedan64 09-29-2009 08:58 AM

This is very difficult to understand. I'll give it a try.
When an Automatic trans with the stock Valvebody is converted to Manual Shift the Valvebody is modified or replaced with a Manual Valvebody. If it has an electric Transbrake it will have a Solenoid to activate the Brake.
It sounds like the Detent/Downshift cable is adjusted too tight. It should downshift to 2nd gear from 3rd at around 3/4 to Full throttle.
The problem with it getting stuck in 2nd may be the Detent valve in the valvebody sticking/binding or other shift valves in the valvebody sticking/binding.
Called Detent cable, Kickdown cable, Passing gear cable.

sqzbox 09-29-2009 09:35 AM

I had a 727 in my dart with reverse/shift, manual shift vave body (sox and martin). In drive (old first gear posistion) it would only shift auto from a stop. Any downshift would have to be manualy shifted to include what you call passing gear. That's why they call it manual shift. There was no detent/downshift cable! Don't know if this applies to the TH350 though, that's just the way it was in mine. :D

CincyMuscle 09-29-2009 02:46 PM

Quote:

Originally Posted by SSedan64
This is very difficult to understand. I'll give it a try.
When an Automatic trans with the stock Valvebody is converted to Manual Shift the Valvebody is modified or replaced with a Manual Valvebody. If it has an electric Transbrake it will have a Solenoid to activate the Brake.
It sounds like the Detent/Downshift cable is adjusted too tight. It should downshift to 2nd gear from 3rd at around 3/4 to Full throttle.
The problem with it getting stuck in 2nd may be the Detent valve in the valvebody sticking/binding or other shift valves in the valvebody sticking/binding.
Called Detent cable, Kickdown cable, Passing gear cable.

Thank you, I will tell that to the guy and see if there's anything he can do about it. I was/am worried it might be something more. With the transbrake being electric would the dead/dying battery have effected the way it shifts to cause the same symptoms or is it mainly just this kick down cable? Either way hes going to have to fix it before I take it but I was just making sure it wasn't something that would cause catastrophic failure.

SSedan64 09-30-2009 12:00 PM

Hard to diagnose without seeing it. As Sqzbox stated above, if it has a Full Manual Valvebody it will only shift by moving the shifter handle and wont have a Detent cable. Others will retain Automatic & Manual shifts.
Since you said it would downshift when you gave it more than 1/2 throttle it must have a Detent cable.
There are also Trans that have air or electric shift solenoids that are activated with RPM switches.

CincyMuscle 09-30-2009 07:17 PM

Ok thank you, I decided against taking in this vehicle as the above problems minor or not were too much of a risk since I really don't know enough about the 350 trans to know what I'm getting into.


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