TH350 lock up problems

[Monty84]

I have a 84 Monte SS with the TH350, this was my dads car so before his passing i never drove it but a couple times so not real familiar with the car. The problem is, everything shifts fine and runs great except when i'm out on the road and i get it up to 65mph its running at about 3200rpm, and as i increase my speed so does the rpms. so lets say i'm running 70mph its tacking somewhere around 4000rpms, is this normal? It just feels like it needs to shift again

 

[TexasT]

That's what overdrive is all about. Do your math with your 3.73 gears(or maybe 3.42 check your trunk spid), tire diameter and speed. If you google you should be able to find an online calculator.


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[v6turbo87]

The lock up only drops the RPM by a few hundred. 4000 @ 70 mph sounds extreamly high. What are you using to measure the RPMs?

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[Monty84]

The car has its own tach in it that shows the rpms...and @TexasT, trying to find answers not smarta@@ responses... and yes it has 3.42 gears in it and yes i know what a standard Turbo 350 sounds like when going into overdrive, but since this car does not have overdrive it just sounds like its way over torqued as speed increases.. most overdrives when it engages you can hear and feel the rpms drop... this one by the time i hit 80mph im clocking almost 5000 which is not normal

 

[v6turbo87]

Actually I ran it in a calculator and with 3.73 gears and 26" tall tires at 70mph it came to 3465 RPMs.

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[Monty84]

what i'm getting is for the 3.42 gears and my 26" tires at 65Mph i should be at 2872.8 RPM's... so wondering if theres a problem with the lock up

 

[v6turbo87]

With 3.42s it should be 3177 @ 70mph. You sure the rear end gears were never changed? Also, not being a wiseguy but the TH350 is not an overdrive transmission. Perhaps you meant you know what lock up feels like. Look up under the break pedal. There may be a switch for the lock up solinoid under there. It should be pushed against the break pedal. It us used to unlock the converter when you step on the brake. These switches often back off from the pedal and you never get lock up.

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[pacecarta]

what i'm getting is for the 3.42 gears and my 26" tires at 65Mph i should be at 2872.8 RPM's... so wondering if theres a problem with the lock up

i would hook another tach to it and make sure of what the rpm is , you cant trust 30yr old Gm stuff

 

[TexasT]

Just tryin ta help there Monty. I'll steer clear.
Just one more thing though , th350 doesn't have overdrive.
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[Monty84]

when i referred to overdrive i was referring to the one with overdrive, i know this one doesnt have it ....and yes, the times i did drive this i seem to recall feeling the lock up engaging which i dont feel now... i appreciate all the help im getting... as for the tach, i have matched it to a racing tach and its right on the money, the rear end is original, this car only has 55,000 original miles on it as my dad babied it and kept it in the garage mostly... dont recall seeing a switch under the break pedal but will check when i get home to make sure, been trying to find a wiring diagram for this but havent yet, the haynes shows nothing about it , thanks again guys, and @TexasT, its cool dude, i've just been getting alot of crap in some of the other forums so my apologies.

 

[TexasT]

Hey we are here to help. This is one , if not the best trans forum I know of. If you went to a Monte Carlo ss forum well, it leaves something to be desired imo.
The switch is up there on the brake pedal. Might be miss adjusted

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[Monty84]

I'll definitely check for that switch when i get home, just never thought to look for it since it shifts perfectly up and down, just felt like it needed to shift again at high speeds... will let you know what i find

 

[TexasT]

Are you getting the 1-2 and the 2-3 that you can feel?
Then the converter isn't locking up?
4k rpm is a lot in third imo which is why I thought it good to calculate what it would be if locked up.
Converter could be taking a dump. Fluid look good? Correct level? Doesn't smell burned?
Do you know if it has had a high stall converter swapped in? Can you see it if you remove the inspection cover? Does the paint look to have been gotten hot?

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[robzombie]

Look for the square plug on driver side of trans above shift linkage. That will tell you if it's a L/U or NLU.

The first thing you need to know is What trans you actually have not what you think it is.

You will get a lot of ship from others and bull ship guesses when you don't take the time to even confirm what you have.

If you are clueless and don't do your homework people will treat you as such.

I'm sure at least one person has asked you to confirm what trans is in the car so they could help you.

The people on this board can and will help anyone, but they need to know exactly what the parts are as well as the symptoms.

If you only give half the info you will only get half ASSED answers.

 

[TexasT]

I knew you'd be along to set the record straight.
Sarcasm just one of my value added services. Haha.
And a free ttt for the op

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[GNRick]

I just started a thread about the brake switch under the dash. http://www.turbobuick.com/forums/threads/bad-brake-switch-under-dash.411916/
The switch has two plugs. One plug has three wires in it for the brake lights. The other plug has two wires, a purple and a grey. With key on and engine off, stick a test light in the purple wire (might appear brown) and see if you are getting a constant 12 volts. If not, your switch is not sending the signal to the transmission to lock up the converter. Of course, this information applies to the GN's, so your mileage may vary. Let us know what you find. Also, keep an eye on that thread reference above in case my information is wrong. Someone already said there is another switch in the circuit but he hasn't said where it is located.

 

[v6turbo87]

The 12 Volt signal is not the locked up signal- one side of the solenoid is supposed to have 12 volts all the time . That 12 volts comes through the brake switch. The switch is there so the convert unlockes immediately when you put your foot on the brake. The ECM sends a ground signal under the appropriate conditions to cause the TCC to activate. It doesn't have to be an electrical problem either. The TCC solenoid could be bad, the valve in the bore of the pump for the locked up could be stuck or the torque converter clutch could be shot. so lots of troubleshooting to do here.

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[Buick Mark]

OOOOOOOOOOOOOOOOOOR, He may not even be shifting into 3rd gear

 

[rag231]

If the rear end is bone stock, it should have a 3.42 rear end. That was the only offering in an 84 SS. What size rear tires do you have? That is the only number not in the equation.

 

[robzombie]

OOOOOOOOOOOOOOOOOOR, He may not even be shifting into 3rd gear

Maybe someone put a powerglide with a 4,500 stall in it when he wasn't looking and a set of 5.13s just for good measure. LOL