TH400 Stuck in Drive
Thread Starter
Racer
Joined: Apr 2007
Posts: 361
Likes: 0
From: Sacramento (Citrus Heights) California
TH400 Stuck in Drive
Alright, this is kind of odd, my transmission is doing some funky stuff:
In park, it feels like it's got power to the rear wheels.
In Reverse, the lights come on but the car won't move (acts like it's in park but there's obviously some resistance on the engine)
In Neutral, acts like drive up until about 10mph, then starts acting like neutral again.
In Drive, works normally but now shifts more smoothly than ever.
This started immediately after I brought the fluid level (hot) up to the line on the dipstick. Do these symptoms indicate overfilling?
In park, it feels like it's got power to the rear wheels.
In Reverse, the lights come on but the car won't move (acts like it's in park but there's obviously some resistance on the engine)
In Neutral, acts like drive up until about 10mph, then starts acting like neutral again.
In Drive, works normally but now shifts more smoothly than ever.
This started immediately after I brought the fluid level (hot) up to the line on the dipstick. Do these symptoms indicate overfilling?
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
Did you check it running in neutral or park on a level surface totally warmed up after driving (it is not good enough to just idle it till warm, you have to drive it to get the trans fluid distributed everywhere)?
Did you add anything other than Dextron? When you checked it, was there foam on the dipstick (indicates it is actually over full)
How low was it?
That stuff aside - did you adjust the linkage or anything else?
Did you add anything other than Dextron? When you checked it, was there foam on the dipstick (indicates it is actually over full)
How low was it?
That stuff aside - did you adjust the linkage or anything else?
Thread Starter
Racer
Joined: Apr 2007
Posts: 361
Likes: 0
From: Sacramento (Citrus Heights) California
Did you check it running in neutral or park on a level surface totally warmed up after driving (it is not good enough to just idle it till warm, you have to drive it to get the trans fluid distributed everywhere)?
Did you add anything other than Dextron? When you checked it, was there foam on the dipstick (indicates it is actually over full)
How low was it?
That stuff aside - did you adjust the linkage or anything else?
Did you add anything other than Dextron? When you checked it, was there foam on the dipstick (indicates it is actually over full)
How low was it?
That stuff aside - did you adjust the linkage or anything else?
Put in Valvoline Hi-Mileage Dexron.
Didn't mess with the linkage at all, but after I added some fluid (about a pint as per the recommendations on the dipstick) the trans would act like it was in "drive" in all gears. Park works but the back end squats a bit like it's getting power, neutral acts like drive until about 10-15mph, then it acts like neutral again, drive acts like drive, and reverse acts like park but the engine won't rev as quickly, indicating that the TC is trying to lock up but can't because it's trying to be in Drive and Reverse at the same time.
The stick has froth on it now, but didn't before. I guess I need to drain and fill it and see what that does.
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
Checked in park after warmed from driving to my FLAPS (Friendly Local Auto Parts Store).
Put in Valvoline Hi-Mileage Dexron.
Didn't mess with the linkage at all, but after I added some fluid (about a pint as per the recommendations on the dipstick) the trans would act like it was in "drive" in all gears. Park works but the back end squats a bit like it's getting power, neutral acts like drive until about 10-15mph, then it acts like neutral again, drive acts like drive, and reverse acts like park but the engine won't rev as quickly, indicating that the TC is trying to lock up but can't because it's trying to be in Drive and Reverse at the same time.
The stick has froth on it now, but didn't before. I guess I need to drain and fill it and see what that does.
Put in Valvoline Hi-Mileage Dexron.
Didn't mess with the linkage at all, but after I added some fluid (about a pint as per the recommendations on the dipstick) the trans would act like it was in "drive" in all gears. Park works but the back end squats a bit like it's getting power, neutral acts like drive until about 10-15mph, then it acts like neutral again, drive acts like drive, and reverse acts like park but the engine won't rev as quickly, indicating that the TC is trying to lock up but can't because it's trying to be in Drive and Reverse at the same time.
The stick has froth on it now, but didn't before. I guess I need to drain and fill it and see what that does.
The froth indicates it may be over full. When they get too much fluid in them they whip it around like mad causing the foam - that plays hell on it. When you drain, watch the refill amount.
The ONLY reason I thiught this is when someone rebuilt my TH400 they did not use the correct dipstick tube (from a th350?) and I did the same thing a little while after I got the car.
Thread Starter
Racer
Joined: Apr 2007
Posts: 361
Likes: 0
From: Sacramento (Citrus Heights) California
This car is such a frankenstein that it probably does have a th350 dipstick, or maybe even a 700R4 dipstick for all I know.
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
It was just too full. So I drained everything, added the correct amount and remarked the stick.
I hope this is the same issue - it is an easy fix!
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
filter replacement
When you replace the filter and remove the old, there should be an o-ring that is on the vertical tube. Look for the o-ring in the attachment cavity if it did not come out with the filter and replace it. If they still sell it, the replacement turbo 400 transmission pan is of so much grearter quality that the original turbo 400 pan. Heavier guage of metal, real good solid piece that is much better at gasket sealing. Torque on the pan bolts is not much to keep from pinching the cork gasket. Without looking it up again I think it is about 11-12 foot pounds.
Last edited by 70ZZ3 96LT4; Dec 10, 2007 at 08:15 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Thread Starter
Racer
Joined: Apr 2007
Posts: 361
Likes: 0
From: Sacramento (Citrus Heights) California
