converter or tranny blew??
Thread Starter
Intermediate
Joined: Aug 2006
Posts: 43
Likes: 0
converter or tranny blew??
i have an automatic th400 3speed
my car will not slip out of first gear until rpms are ridiculously high that was going on for a couple days. and now it feels like the tranny keeps slipping and the engine just cant connect with it...so on the way back to my house there was smoke pouring out the back of the car and the engine stayed ideling high because today it just would not shift outta first. it also feels like the tranny keeps slipping the engine catches it barely at times.
the engine is fairly new its an overhauled 327 its got a 350 cam but not pushing too much horsepower maybe around 250hp . the tranny i am unsure if it was the original or not...but what do u think my issue is and whats the cost for trannys and or converters?? WWUD??
my car will not slip out of first gear until rpms are ridiculously high that was going on for a couple days. and now it feels like the tranny keeps slipping and the engine just cant connect with it...so on the way back to my house there was smoke pouring out the back of the car and the engine stayed ideling high because today it just would not shift outta first. it also feels like the tranny keeps slipping the engine catches it barely at times.
the engine is fairly new its an overhauled 327 its got a 350 cam but not pushing too much horsepower maybe around 250hp . the tranny i am unsure if it was the original or not...but what do u think my issue is and whats the cost for trannys and or converters?? WWUD??
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
sounds like the torque converter to me.....if the engine is revving high and it seems like its not connecting to the trans it may not be....i'm not sure what the smoke is unless you burst a trans line and its shooting onto the exhaust .....i bet this would also cause the trans to operate goofy
Safety Car
Joined: Dec 2005
Posts: 4,270
Likes: 20
From: Central Michigan
Sounds like the diaphram in the modulator is blown. Crawl under the car and unhook the vacuum line going to the modulator(pass side of trans). If there is fluid in it, replace it. That should solve the problem
Racer
Joined: Mar 2006
Posts: 309
Likes: 0
From: Ocean City MD
1 more vote for modulator. When it fails the trans relys on the govenor for shifts and they can be very high. Also if the diaphram has a hole you will get smoke as the motor takes in the trans fluid.
Safety Car
Joined: Dec 2005
Posts: 4,270
Likes: 20
From: Central Michigan
The vacuum modulater senses engine load by the vacuum signal. A rubber diaphram inside the modulater reacts to this vacuum and in doing so moves a valve within the transmission valve body, allowing it to shift into second or third. If the diaphram was torn, it can't move, thus it won't shift. Instead of pulling on the diaphram, transmission fluid will instead be sucked into the engine, creating the smokescreen you see blowing out behind you.
To check this, just pull the vacuum hose hose off at the modulater, if transmission fluid comes out, that's your problem. You may even want to test it for vacuum also if you don't see any fluid, just to cover your bases.
If you have to remove the modulater, drain the trans fluid first and remove the U-shaped clip holding it in place, and pull it out. You should be able to buy one at the local parts store for around $15.
Good luck, let us know how it goes
To check this, just pull the vacuum hose hose off at the modulater, if transmission fluid comes out, that's your problem. You may even want to test it for vacuum also if you don't see any fluid, just to cover your bases.
If you have to remove the modulater, drain the trans fluid first and remove the U-shaped clip holding it in place, and pull it out. You should be able to buy one at the local parts store for around $15.
Good luck, let us know how it goes
Thread Starter
Intermediate
Joined: Aug 2006
Posts: 43
Likes: 0
cool info thansk for the steps... some of u guys just know way too much SHYT 
but thanks im new to vettes, in my early twenties and have worked on imports most of my life..figured id get into american muscle but i mean these vettes have LOTS of problems, yes the car is 30+ years old but DAMn
but thanks im new to vettes, in my early twenties and have worked on imports most of my life..figured id get into american muscle but i mean these vettes have LOTS of problems, yes the car is 30+ years old but DAMn
Safety Car
Joined: Aug 2001
Posts: 3,892
Likes: 13
From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Originally Posted by onelifeoneride
cool info thansk for the steps... some of u guys just know way too much SHYT
but thanks im new to vettes, in my early twenties and have worked on imports most of my life..figured id get into american muscle but i mean these vettes have LOTS of problems, yes the car is 30+ years old but DAMn
but thanks im new to vettes, in my early twenties and have worked on imports most of my life..figured id get into american muscle but i mean these vettes have LOTS of problems, yes the car is 30+ years old but DAMn
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Drifting
Joined: Feb 2005
Posts: 1,438
Likes: 2
From: Melrose Florida
Another modulator vote...easy to change, and inexpensive part.
Passenger side, one bolt holding a u-shaped hold-down in place (like a distributor clamp). One vacuum line slipped onto nipple.
It's OK if the new part looks different from the old one.
I don't remember having to drop pan or change fluid to change modulator, might be messy otherwise though.
It is an excellent time to replace fluid and trans filter.
Steve
Passenger side, one bolt holding a u-shaped hold-down in place (like a distributor clamp). One vacuum line slipped onto nipple.
It's OK if the new part looks different from the old one.
I don't remember having to drop pan or change fluid to change modulator, might be messy otherwise though.
It is an excellent time to replace fluid and trans filter.
Steve
