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#1055160 - 01/05/18 05:03 AM Surging Cruise and erratic TCC Lock up  
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ChasUno Offline
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ChasUno  Offline
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Bradenton, FL
Couple of issues here that may or may not be related. I wonder if anyone can shed any light and how I can resolve them?

As most of you know, my car is a 1986 Monte Carlo SS with standard 305 V8, running standard Q-Jet and CCC system. I have replaced numerous parts (i.e. gaskets, TPS, rotor arm, cap, O2 sender, all vacuum lines etc.) as well as set parameters to factory specifications (TPS, MC dwell, ignition timing etc.) SES Light works, goes out on start up. No trouble codes stored in the computer (I access the codes and computer with a Brainmaster II scanner).

Issues:

TH200-4R trans very finicky about staying in 4th gear lock up, especially at lower speeds (under 55mph). Sometimes it seems that the slightest touch of the accelerator causes it to come out of lock up, even at speeds over 50 mph.

Cruise control, when engaged, surges seemingly randomly. Sometimes it's better than others, other times it repeatedly lurches and holds back especially at lower speeds.

What I have noticed over the past month or so is that the speedo has become more jumpy, flicking as much as 10 - 15 mph over the cruising speed and sometimes wobbling by a good few mph when travelling at a steady speed. As per the cruise, sometimes it's worse than others.

I know that cruise relies on the VSS (vehicle speed sensor), which runs off the speedo cable, so I'm assuming the surging cruise is speedo cable and VSS related? However, does the trans lock up also use the VSS signal at all? Is the fluctuating speed signal via the VSS confusing the computer and making it disengage the lock up? If not, what could be causing my trans lock up to disengage itself so easily?


1986 Monte Carlo SS

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#1055161 - 01/05/18 06:11 AM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
Chas fix the cable/erratic speedo problem first, the jumpy speedo drives the VSS nuts. You need to remember you're dealing with 40 year old technology. It's a very simple circuit but needs to see smooth consistent input to the speedo.

The cruise diaphragm is vac operated, same thing, it's 35 years old, it doesn't flex the way it did when new. I have factory cruise on my engine, only have the rod to the carb installed when I need to make a 2 hour trip up the turnpike. Because it's a stick car cruise is 1 to 1, direct drive. What I find is when you want to accel say from 65 to 67 and tap the accel two times you'll get a surge instead of that smooth mph increase like you do in the new cars. I attribute that to the diaphragm.

There are two switches at the brake pedal. White switch is cruise, has a vac hoses connected. The other switch controls brake lights and TCC. Both switches need to be adjusted properly.
Bob

#1055225 - 01/10/18 06:37 AM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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ChasUno Offline
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ChasUno  Offline
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Bradenton, FL
Cheers as always Bob, and I agree, the erratic speedo needs to be sorted first to hopefully solve some of the issues I am getting.

Absolutely understand that I am running 40 year old technology, and some parts are just not going to be working as well as they did back in the 80's. However, I'm going to try my best to get things running as well as possible, and as GM intended!

As my cruise seems to vary its behaviour depending on how well the speedo is behaving, it is logical that I should get the speedo working smoothly first, which will also calm the VSS readings, which in term should stabilise the ECM.

Looking on the Autozone website, they only seem to sell a form of speedo cable repair kits. Any recommendations as to where I can purchase a new cable?

This is what Autozone offers:

https://www.autozone.com/drivetrain/speedometer-cable/pioneer-speedometer-cable/1672_345317_6211


Last edited by ChasUno; 01/10/18 06:38 AM.

1986 Monte Carlo SS

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#1055226 - 01/10/18 06:46 AM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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ChasUno Offline
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ChasUno  Offline
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Bradenton, FL
Or would this cable be suitable?

https://www.ebay.com/itm/Napa-48824-Speedometer-Cable-100-Inch-Length/182784825948?fits=Model%3AMonte+Carlo%7CSubmodel%3ASS&epid=622475610&hash=item2a8ed31a5c:g:mZ4AAOSwpuBZxtEG&vxp=mtr


1986 Monte Carlo SS

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#1055232 - 01/10/18 02:33 PM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
I hate to say I'm an internet shopper, but. Go to rockauto and look at your choice there, speedo cables are listed under "interior".
Your 86 should have only one cable, earlier years of Monte used two cables. Pull the cable and measure it's length. Even though it was 1998 when i replaced the cable in the 86 I show a 08160 as the part i installed, probably was an ATP.
Bob

#1055242 - 01/11/18 02:28 PM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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Witness86SS Offline
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Hatfield, PA
Thanks for this discussion. It's made me realize that I painted all of the bracket pieces where i connected my main ground cable. I have symptoms that i have been chalking up to needing a beefier alternator/battery/better ignition wires etc..

Last edited by Witness86SS; 01/11/18 02:29 PM.

Justin
1986 Black SS
350 L05 - Hooker Longtubes - FlowMaster True Dual 2.5" - Electric Cutouts - Electric Fans - Transcooler
#1055259 - 01/12/18 03:33 AM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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Buick Runner Offline
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Dharma station 1 the Hydra
Bad grounds are a major source of gremlins.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1055262 - 01/12/18 02:09 PM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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Witness86SS Offline
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Hatfield, PA
I thought my post ended up on this thread. wasn't meant to go here.


Justin
1986 Black SS
350 L05 - Hooker Longtubes - FlowMaster True Dual 2.5" - Electric Cutouts - Electric Fans - Transcooler
#1055697 - 02/06/18 06:04 PM Re: Surging Cruise and erratic TCC Lock up [Re: ChasUno]  
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basemonte Offline
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basemonte  Offline
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On the trans dropping 4th gear very easily, would check the adjustment on the throttle valve cable. I check it with a line pressure gauge such that with the slightest motion of the accelerator cable the line pressure increases.

#1055847 - 02/12/18 04:39 AM Re: Surging Cruise and erratic TCC Lock up [Re: basemonte]  
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ChasUno Offline
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ChasUno  Offline
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Posts: 259
Bradenton, FL
Originally Posted by basemonte
On the trans dropping 4th gear very easily, would check the adjustment on the throttle valve cable. I check it with a line pressure gauge such that with the slightest motion of the accelerator cable the line pressure increases.


Thanks for the suggestion, though it's not dropping 4th easily, it's dropping out of TCC lock up easily when in 4th (I can see this happening via my Brainmaster scanner). The trans remains in 4th, it's the torque converter clutch lock up that drops in and out.

I have also set my TV cable as per the GM service manual. The trans otherwise shifts fine

Just need to get round to replacing the speedometer cable and see if that helps matters.


1986 Monte Carlo SS

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