is it the tranny?
Thread Starter
Racer
Joined: Nov 2008
Posts: 442
Likes: 6
From: jacksonville Florida
is it the tranny?
So I think my transmission is starting to go. The car drives smooth until 4th gear, the minute my tranny shifts from 3rd to 4th the car starts to vibrate and ride rough. It is really bad below 1,000rpm when in the 35-45mph range, if the speed limit is around there i have started leaving the shifter in 3rd to prevent it from shifting up or i give it some gas to downshift. Above 1000rpm it doesn't shake as bad but you can still feel it and if you try to accelerate in 4th the vibration is amplified, especially if going up a bridge or the A/C is on. MY main question is, what should i do to diagnose that my tranny really is the problem and what are my options. My car is a 1982 with the crossfire still working on the orginal engine and tranny with about 160,000 miles on the car. I already did a filter kit in hopes that it would help but i didnt really notice a change. I have also been checking the engine, found a vacuum leak and fixed that but problem still prevails as well as replaced the plugs and checked the wires, still the problem remains.
All input appreciated, thanks
All input appreciated, thanks
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
If you can't duplicate the vib in 3rd gear, it might be the trans or torque converter locking up and amplifying a misfire.
One way to check it get the car vibrating and hold the brake pedal at the same time. Just enough to turn the brake lights on without engaging the brakes. This will unlock the torque converter TC . If the vib goes away, start looking for a misfire.
One way to check it get the car vibrating and hold the brake pedal at the same time. Just enough to turn the brake lights on without engaging the brakes. This will unlock the torque converter TC . If the vib goes away, start looking for a misfire.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Advise and best bang for the buck. Buy a Hypertec chip/prom for your 82 CFI. It takes less than 5 minutes to install with a nut driver and your car will be an entirely different animal!!! Beside better throttle response it also changes the trans shifting and TC lock up.
You just reminded me that my 82 use to chug a little at @40mph. The chip fixed that.
You just reminded me that my 82 use to chug a little at @40mph. The chip fixed that.
Thread Starter
Racer
Joined: Nov 2008
Posts: 442
Likes: 6
From: jacksonville Florida
Alright I did that today and whenever I pressed the brake the vibes went away and the rpms shot up about 4-500rpm but drove smoothly. Is that a safe diagnosis for misfire issue?
hugie82 did the chip affect your mpg?
hugie82 did the chip affect your mpg?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
Your lockup clutch is coming on immediately in 4th gear causing it to "shuck 'n' jive". Normally, lockup would not come on immediately.
If you installed an O/D tranny in the car, did you also install a lockup clutch controller? If not, you should leave the lockup clutch OFF except when at steady speed on the Interstate or state highway. The controller will manage the lockup clutch for you, so that you don't get that kind of bucking.
If your car came with an O/D tranny w/lockup, there is something amiss with the lockup control system.
If you installed an O/D tranny in the car, did you also install a lockup clutch controller? If not, you should leave the lockup clutch OFF except when at steady speed on the Interstate or state highway. The controller will manage the lockup clutch for you, so that you don't get that kind of bucking.
If your car came with an O/D tranny w/lockup, there is something amiss with the lockup control system.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
His 82 came with a 700R4 .. The converter clutches could be worn. Or your fuel pressure could be low causing it to lean out or you have a vac leak .. So it is a fuel injection issue or a torque converter issue I personally think it is a F/I issue. Or timing and spark issue.
Thread Starter
Racer
Joined: Nov 2008
Posts: 442
Likes: 6
From: jacksonville Florida
yeah its still the factory 700R4, so how ever that is set up. What tests/diagnostics can I do to help narrow down the problem? Obviously a timing light to check timing but how can i establish which plug is misfire or establish that it is a F/I issue?
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Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Check the fuel pressure first and also look for vacuum leaks . Also Look for cross fire issues i am more a tranny guy and your complaint although could be a tranny sounds like motor issues causing the trans to lock/unlock and bog
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Take the car to 40mph in 3rd ,, see if it locks up at a steady 40mph check it by tapping break peddle. If it locks and unlocks and is not bucking put it in 4th and run 40mph test same way of it starts to buck and stutter I would suspect f/i issue .
He is at 1000rpm in 4th locked up at 40mph the load on the motor is massive but his hp and torque are at lawnmower levels , the f/i when working properly will meter the fuel so he can maintain and accelerate from that situation. That is the main reason a O/D in a carbed car with tall gears is a bad idea ,It will do what the OP is describing and why f/i and over drives came onto the the scene together .
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
Sounds to me as if your converter is staying lock up, that's why when you hit the break( lock up disengauges when the Brake light comes on ) the vibration goes away. The solutions to this is either to put a pressure switch on fourth gear do that the trsny is only locked in fourth gear or buy a painless kit. Or at least this was the way I did it, my car didn't come with the 700r4. Good luck.
Drifting
Joined: Jun 2013
Posts: 1,269
Likes: 226
From: Cocoa FL
Is there a way to "unplug" the converter from the tranny? Doesn't it have a wire that connects to it to make the converter turn on and off? Just throwing stuff on the wall. Might be a quick way to see of the converter is causing the issue - ???
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
On some years it's safe to unplug the converter, other years it'll overheat the tranny. Don't remember which years.
Thread Starter
Racer
Joined: Nov 2008
Posts: 442
Likes: 6
From: jacksonville Florida
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
So I think my transmission is starting to go. The car drives smooth until 4th gear, the minute my tranny shifts from 3rd to 4th the car starts to vibrate and ride rough. It is really bad below 1,000rpm when in the 35-45mph range, if the speed limit is around there i have started leaving the shifter in 3rd to prevent it from shifting up or i give it some gas to downshift. Above 1000rpm it doesn't shake as bad but you can still feel it and if you try to accelerate in 4th the vibration is amplified, especially if going up a bridge or the A/C is on. MY main question is, what should i do to diagnose that my tranny really is the problem and what are my options. My car is a 1982 with the crossfire still working on the orginal engine and tranny with about 160,000 miles on the car. I already did a filter kit in hopes that it would help but i didnt really notice a change. I have also been checking the engine, found a vacuum leak and fixed that but problem still prevails as well as replaced the plugs and checked the wires, still the problem remains.
All input appreciated, thanks
All input appreciated, thanks
Try this?
Hold your foot steady on the gas.. take your other foot and bump the brake enough to turn on the brake lights and make the CC clutch come off.. You should see the tach jump..
If your problem goes away? It's probably an engine performance issue.
(Once the converter clutch locks? EVERYTHING comes back to the driver.. Every miss, every hiccup. The fluid coupling in the converter will mask many engine performance woes. But you can feel them all when that clutch comes on.)
Melting Slicks
Joined: Nov 2013
Posts: 3,451
Likes: 336
From: Greater Cincinnati Area.
Alternatively.. If you think the converter clutch is weak/slipping..
Some scan tools (Or you can manually) lock the CC in gear, at a stop.. and it should kill the engine.
Be very careful performing this test.
Some scan tools (Or you can manually) lock the CC in gear, at a stop.. and it should kill the engine.
Be very careful performing this test.
Last edited by confab; Mar 23, 2014 at 12:41 AM.
Thread Starter
Racer
Joined: Nov 2008
Posts: 442
Likes: 6
From: jacksonville Florida
Thats not true .. His is the first 700R4 used in what became a long history used up until today (4l60) . His unit will lock up at light loads in high gears like 3 and 4th .. That in and of it self was a issue back then but not what he is describing.
Take the car to 40mph in 3rd ,, see if it locks up at a steady 40mph check it by tapping break peddle. If it locks and unlocks and is not bucking put it in 4th and run 40mph test same way of it starts to buck and stutter I would suspect f/i issue .
He is at 1000rpm in 4th locked up at 40mph the load on the motor is massive but his hp and torque are at lawnmower levels , the f/i when working properly will meter the fuel so he can maintain and accelerate from that situation. That is the main reason a O/D in a carbed car with tall gears is a bad idea ,It will do what the OP is describing and why f/i and over drives came onto the the scene together .
Take the car to 40mph in 3rd ,, see if it locks up at a steady 40mph check it by tapping break peddle. If it locks and unlocks and is not bucking put it in 4th and run 40mph test same way of it starts to buck and stutter I would suspect f/i issue .
He is at 1000rpm in 4th locked up at 40mph the load on the motor is massive but his hp and torque are at lawnmower levels , the f/i when working properly will meter the fuel so he can maintain and accelerate from that situation. That is the main reason a O/D in a carbed car with tall gears is a bad idea ,It will do what the OP is describing and why f/i and over drives came onto the the scene together .