Ya gotta move to a 200 4R or a 700 R4 if you want an automatic with overdrive to reduce the RPM's.
trannys
Thread Starter
Cruising
Joined: Jun 2008
Posts: 10
Likes: 0
trannys
Is There Any Problems With Swapping A Th350 With An Th400 On A79 Vette Frameing .if Anybody Could Let Me Know It Would Be Appreciated Before I Dismantle Every Thing .im A New Member And I Restored My 79 And My Friend Gave Me A Redone Th400 After The Fact As Per Usual . Too Ge My Highway R.p.m. Down
Burning Brakes
Joined: Aug 2006
Posts: 1,155
Likes: 0
From: San Diego California
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The THM400 tranny is a much stronger trans than the 350 unit...but I don't know that you need more strength than the 350 [for the stock engine]. But the 400 also is a HP 'waster'...not very efficient. An overdrive tranny is a much better replacement for your 350..but it will cost a good piece of change. If your 350 is well worn and the 400 is fresh (and not much money), the 400 will be a nice unit for you. If you plan on doing much highway driving, the 200R4 will eventually pay for itself in the saved gas money.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
OP, all the above comments are correct, and if you restored the car doing most of the work yourself, you CAN....with some reading, and a bit of study ....rebuild your own 200 4r tranny and it's damn near a bolt in swap for the 350, unless you have a super HP engine, it will last fine, as I did my own which is in the '72 vert here for some 3 years now....runs like a charm.....
PM me or 6'er Danny for the lo down on how to build one, and what/where to read.....not as hard as it looks, seriously....
you can get it done for 5-600 bux or so, maybe less....
PM me or 6'er Danny for the lo down on how to build one, and what/where to read.....not as hard as it looks, seriously....
you can get it done for 5-600 bux or so, maybe less....
Thread Starter
Cruising
Joined: Jun 2008
Posts: 10
Likes: 0
trannys
my 350 is leaking like anything the 400 was givin to me thats my i would like to know if there is any major modification that needs to be done and im running about 435hp i was told it was a stronger tranny
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
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The 400 would be better than the 350 for your application. However, if you want reliability, you should do a good rebuild on the 400 or purchase a beefed-up 700R4 to manage that much HP. If you don't intend on going WOT all that much, the 400 should do fine....if it is in good condition.
Drifting
Joined: Jul 2004
Posts: 1,695
Likes: 65
From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
2017 C3 of Year Finalist
Cruise-In VIII Veteran
St. Jude Donor '07
To answer your original question, to swap the 400 in where the 350 is now, you will need to measure the over all length of the 350 and the 400. this will tell you if you need to adjust the driveshaft length. The 400 should bolt in on top of the existing crossmember. It will use the holes bolting in the 350 tranny bracket. You will need to obtain the 400 tranny yoke for the corvette. The standard "press in the universal joint syyle" wil not work and the 350 yoke will not fit the 400. This will most likely be your biggest expense. The shifter will work and so should the interlock if it is still there. I am not sure about the speedo gear in the tranny. You may need to use the one from the 350 to get everything reading right.