Turbo 400 Questions
Thread Starter
Drifting
Joined: May 2004
Posts: 1,258
Likes: 0
From: Huntsville Alabama
Turbo 400 Questions
Ok well i got my new yearone creat motor in and man does this thing go. Now my th400 is wanting to slip it feels like. My question is how much hp/tq can a stock th400 handel. Also What is the First gear Ratio in the th400. I dont want to get in to rear gear changes the car is a 75 so it should have the 3.08 rear in it. It was a L48. What can i expect to pay to have it rebuilt and beefed up if needed or would I be better off buying a B&M or TCI th400 from summit.
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
Originally Posted by Silver00V6Camaro
Ok well i got my new yearone creat motor in and man does this thing go. Now my th400 is wanting to slip it feels like. My question is how much hp/tq can a stock th400 handel. Also What is the First gear Ratio in the th400. I dont want to get in to rear gear changes the car is a 75 so it should have the 3.08 rear in it. It was a L48. What can i expect to pay to have it rebuilt and beefed up if needed or would I be better off buying a B&M or TCI th400 from summit.
Last edited by 2000FRCZ19; Nov 30, 2006 at 05:01 PM.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Silver00V6Camaro
Ok well i got my new yearone creat motor in and man does this thing go. Now my th400 is wanting to slip it feels like. My question is how much hp/tq can a stock th400 handel. Also What is the First gear Ratio in the th400. I dont want to get in to rear gear changes the car is a 75 so it should have the 3.08 rear in it. It was a L48. What can i expect to pay to have it rebuilt and beefed up if needed or would I be better off buying a B&M or TCI th400 from summit.
This may be a silly question, and you may have done this...but did you check your transmission fluid level? I know most auto transmissions will start to slip if their a little short on fluid, or if the fluid has degraded from heat and wear. Look into that maybe.
TH400s can handle quite a bit right from the factory...but it's probably at least two decades old right...if not more. A rebuild should cost you about $600 - $1000 depending on how strong you want it.
If you get into the realm of rebuilding...I would suggest a trip to Bowtieoverdrives.com. Buy one of them kits, maybe a stage II kit for just over $1000 and you'll have the same first three gears, an overdrive gear, and it'll handle the HP just fine.
Thread Starter
Drifting
Joined: May 2004
Posts: 1,258
Likes: 0
From: Huntsville Alabama
My motor puts out 425hp/438tq. and yes i checked the fluid i have a new B&M Aluminum pan that added 2 more quarts of fluid to it. and yes i installed the filter correctly to compensate for the larger pan. I also added a bottle of lucas transmssion stop slip which helped a little but when you get into it still just does not want to take the power.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Silver00V6Camaro
My motor puts out 425hp/438tq. and yes i checked the fluid i have a new B&M Aluminum pan that added 2 more quarts of fluid to it. and yes i installed the filter correctly to compensate for the larger pan. I also added a bottle of lucas transmssion stop slip which helped a little but when you get into it still just does not want to take the power.
How old is the trans? Have you any knowledge of a rebuild or work done to it?
Thread Starter
Drifting
Joined: May 2004
Posts: 1,258
Likes: 0
From: Huntsville Alabama
Supposedly rebuilt about 2 years ago when i had my first motor built but i can only go by what the redneck that built my motor told me and after dealing with the old motor I am wonderin about the transmission.
Burning Brakes
Joined: Aug 2002
Posts: 1,146
Likes: 10
From: Scottsboro Alabama
Originally Posted by Silver00V6Camaro
Supposedly rebuilt about 2 years ago when i had my first motor built but i can only go by what the redneck that built my motor told me and after dealing with the old motor I am wonderin about the transmission.
Are you sure you drained out all the sawdust when you changed pans?
Thread Starter
Drifting
Joined: May 2004
Posts: 1,258
Likes: 0
From: Huntsville Alabama
Yup Im pretty sure all of the saw dust came out. But seriously if they did anything or had anything done to the transmission like they said about the motor I think i am going to need a rebuild or just buy a new one. Like i did the motor.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
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
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 87
From: State of Confusion
The gear-ratios of 'standard', OEM THM400s are:
1st Gear - 2.48:1
2nd Gear - 1.48:1
3rd Gear - 1.00:1
TCI offers extra-deep gear-sets, so your 3.08s will feel quicker off the line, for a few hundred dollars, in ratios of 2.75:1, 1.57:1, and 1.00:1.
1st Gear - 2.48:1
2nd Gear - 1.48:1
3rd Gear - 1.00:1
TCI offers extra-deep gear-sets, so your 3.08s will feel quicker off the line, for a few hundred dollars, in ratios of 2.75:1, 1.57:1, and 1.00:1.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Glensgages
The gear-ratios of 'standard', OEM THM400s are:
1st Gear - 2.48:1
2nd Gear - 1.48:1
3rd Gear - 1.00:1
TCI offers extra-deep gear-sets, so your 3.08s will feel quicker off the line, for a few hundred dollars, in ratios of 2.75:1, 1.57:1, and 1.00:1.
1st Gear - 2.48:1
2nd Gear - 1.48:1
3rd Gear - 1.00:1
TCI offers extra-deep gear-sets, so your 3.08s will feel quicker off the line, for a few hundred dollars, in ratios of 2.75:1, 1.57:1, and 1.00:1.
How do those ratios differ from the TH350, and if you have the info, cross those with the 200R4 and the 700R4. Thanks.
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 87
From: State of Confusion
Originally Posted by Durango_boy
How do those ratios differ from the TH350, and if you have the info, cross those with the 200R4 and the 700R4. Thanks.
A THM350 is almost identical (ratio-wise ) to the mother-of-all-Turbo/Hydros at 2.52/1.52/1.....
I think the 200-4r is something-like 2.75 (? )/1.60-ish (? )/1/.66-ish (? ).....
Last edited by Glensgages; Dec 2, 2006 at 08:04 PM.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Glensgages
The 700R4 in my '82 Cease-Fire is 3.06/1.63/1/.7.....
A THM350 is almost identical (ratio-wise ) to the mother-of-all-Turbo/Hydros at 2.52/1.52/1.....
I think the 200-4r is something-like 2.75 (? )/1.60-ish (? )/1/.66-ish (? ).....
A THM350 is almost identical (ratio-wise ) to the mother-of-all-Turbo/Hydros at 2.52/1.52/1.....
I think the 200-4r is something-like 2.75 (? )/1.60-ish (? )/1/.66-ish (? ).....
Wonderful...thanks so much.
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 87
From: State of Confusion
Originally Posted by Durango_boy
Wonderful...thanks so much.
since I moved in September, I don't have all of my data handy.....
For anybody contemplating having their THM350 or THM400 rebuilt, who has relatively 'tall' rear-gearing, and wants more off-the-line punch (especially if they are retaining an under-powered, numbers-matching or era-correct small-block ), I'd strongly think about the lower gear-sets from TCI (or other, reputable vendors ):
they'd make the original poster's 3.08s 'feel-like' 3.36s, make 3.36 rear-gears launch like 3.70s, and 3.70 cogs would accelerate as-if 4.11s have been installed, while not-hurting RPM-to-MPH ratios in 3rd gear, at highway speeds.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Alwyn678
They sure seem to be bullet proof....................Just need one more gear at speed!
That's why the TH200R4 is supposed to be so good. From what I hear the gears are very close to driving with a TH350, but with an over drive gear.