81 transmission OD shift ??
Thread Starter
Pro
Joined: Dec 2001
Posts: 582
Likes: 72
From: Near Raleigh NC
81 transmission OD shift ??
I had mine gone through at 40k, only at 52K now, and ever since I have had it, I don't feel a shift for the OD clutch, I was told to brake slightly and feel the down shift from OD. They said no evidence the OD 2nd and 3rd clutches won't work, all internals are new. Can some 81'ers elaborate. I have heard MAP sensor is not closing loop, or ECM may not be getting the message. thoughts. :smash:
Heel & Toe
Joined: Jan 2002
Posts: 15
Likes: 0
From: MOBILE AL
Re: 81 transmission OD shift ?? (81VETTOM)
Maybe I'm wrong,but,I thought the 81's had a three speed 350 trans with a lock up torque converter that was designed to be able to lock in both second and third gears.If I'm correct you should still be able to feel the converter lock up under mild acceleration but it won't be nearly as pronounced as the shift into overdrive like a 700 trans with a fourth gear.
Good Luck
Tom
Good Luck
Tom
Burning Brakes
Joined: Dec 2000
Posts: 1,183
Likes: 2
From: Des Moines Iowa
Re: 81 transmission OD shift ?? (81VETTOM)
Neo Fender and Tommay are correct. The torque convertor is controled by ECM on the '81. I've noticed that mine doesn't seem to want to lock up when cold and I first drive on the highway, but after a few miles, then it seems like the torque convertor does go into the lock up mode..........Always thought it had to do with emmisions/engine not being completely warm, and never really worried about it too much, since the lock up does seem to eventually work.
Incidently, right after I got the '81 five years ago, I changed transmission oil and filter without really have driven it at all, and the wire connection inside the transmission was unhooked, so I hooked it up.......anyone know why previous owner would have unhooked this wiring connection????
Incidently, right after I got the '81 five years ago, I changed transmission oil and filter without really have driven it at all, and the wire connection inside the transmission was unhooked, so I hooked it up.......anyone know why previous owner would have unhooked this wiring connection????
Drifting
Joined: Mar 2001
Posts: 1,411
Likes: 2
From: St. Louis, Missouri
Re: 81 transmission OD shift ?? (john's '81 mouse)
John,
The lock-up function is disabled until the engine (coolant) reaches a certain temperature (at least w TH-700s this is the case). This is supposed to help the engine warm-up quicker so your transmission may be working as advertised.
No, I don't know why anyone would want to disable the lock up function.
The lock-up function is disabled until the engine (coolant) reaches a certain temperature (at least w TH-700s this is the case). This is supposed to help the engine warm-up quicker so your transmission may be working as advertised.
No, I don't know why anyone would want to disable the lock up function.
Burning Brakes
Joined: Dec 2000
Posts: 1,183
Likes: 2
From: Des Moines Iowa
Re: 81 transmission OD shift ?? (Neo Fender)
Neo Fender, thanks for the response, as you can tell, I suspected it was something like that, but nice to have my theory substantiated by another fourm member.
Thread Starter
Pro
Joined: Dec 2001
Posts: 582
Likes: 72
From: Near Raleigh NC
Re: 81 transmission OD shift ?? (john's '81 mouse)
I wondered if the temp was a factor, but it does get hot, and now I have added a separate trans cooler, but didn't make any difference except reduce heat in the car and OD still won't work. If 200rpm is only difference, I guess i won't worry about it. I guess its possible the ECM isn't seeing the temp. I have another ECM, maybe I swap just to see. darn another project :smash:
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Drifting
Joined: Mar 2001
Posts: 1,411
Likes: 2
From: St. Louis, Missouri
Re: 81 transmission OD shift ?? (81VETTOM)
I'm going by memory here but I believe the coolant temp switch is in series with the lock-up switch. The lock-up is restricted by engine temp, not transmission temp.
Heel & Toe
Joined: Jan 2002
Posts: 15
Likes: 0
From: MOBILE AL
Re: 81 transmission OD shift ?? (john's '81 mouse)
Best I can recall it was pretty common back in the early eighties to disable the lockup.A lot of those converters would lock up at about fourty and switch in and out a lot in city driving and some didn't unlock as easily as they should and make a little drivetrain flutter that felt like a slight engine miss to some people.Folks just weren't used to them and didn't like them and would rather just have them disabled.
Le Mans Master
Joined: Aug 2000
Posts: 9,662
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From: Semper ubi, sub ubi
Cruise-In VI Veteran
Cruise-In VII Veteran
Re: 81 transmission OD shift ?? (TOMMAY)
Tommay is 100% correct, it was very common at dealerships to do that in the early 80's. They did it to my wife's car when she complained about it slipping in and out of lockup.
Melting Slicks
Joined: Jan 2001
Posts: 2,187
Likes: 0
From: Rotterdam
Re: 81 transmission OD shift ?? (Smokehouse69)
Tommay is 100% correct, it was very common at dealerships to do that in the early 80's. They did it to my wife's car when she complained about it slipping in and out of lockup.
Interesting.....what exactly should I do to "remove" the lock up function on a 82?It's the one thing I don't like at the car,specially in city driving.(what I do for 80%....)
Heel & Toe
Joined: Jan 2002
Posts: 15
Likes: 0
From: MOBILE AL
Re: 81 transmission OD shift ?? (Pete Z)
Not wanting to tell you what to do,but it would probably be best to not disable the lockup on a 700 r4.The slipping converter increases heat in the fluid and can lead to premature failure.If you do disable it be sure to run an aux trans cooler and monitor fluid for signs of overheating.
I've got a 76 Silverado with a 454 and 700r4 and it seems to be ok without the lock up.But I have never taken it on a long trip where it would have a chance to really heat up,but it does have the aux cooler in addition to the cooling provided by the radiator.
I've got a 76 Silverado with a 454 and 700r4 and it seems to be ok without the lock up.But I have never taken it on a long trip where it would have a chance to really heat up,but it does have the aux cooler in addition to the cooling provided by the radiator.
Thread Starter
Pro
Joined: Dec 2001
Posts: 582
Likes: 72
From: Near Raleigh NC
Re: 81 transmission OD shift ?? (TOMMAY)
ok; so just to check, the coolant switch is what may be the culprit. I know it was not disabled by me or the trans builder. Is there a way to check the switch? :smash:
