TH350 to TH400
Thread Starter
Heel & Toe
Joined: Oct 2005
Posts: 22
Likes: 0
TH350 to TH400
I am having problems with my TH350 in my 79 and have an opportunity to get my hands on a TH400. Any words of wisdom would be appreciated regarding the pros, cons, mods, etc.
Thanx in advance...
Thanx in advance...
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
NO question the 400 is much stronger tranny, but both are antiquated in today's world, you need overdrive, and if doing any swaps, may as well go for a 200 4r and get over with it...
a 400 is great for really high HP drag use, but other than 600 hp or up, it's not necessary......
well then again if towing a power boat up a mountain at 10% grade for 80-100 mph is your gig...maybe a 400 IS the way to go....NO overdrive can do that....
GENE
a 400 is great for really high HP drag use, but other than 600 hp or up, it's not necessary......
well then again if towing a power boat up a mountain at 10% grade for 80-100 mph is your gig...maybe a 400 IS the way to go....NO overdrive can do that....
GENE
Thread Starter
Heel & Toe
Joined: Oct 2005
Posts: 22
Likes: 0
Thanx for the info. I am not a tranny expert so any info helps. What do I gain w/ the 200 4r other than overdrive. I drive my car on weekends and am looking for good performance on the street and of course reliability and durability. If I can get a TH400 for $0 from a friend, how strong should I consider spending $$$ for another option?
I have read that I would need to mod the cross member and the drive shaft for a TH400. I also read something about a switch for downshift on hard accel. Any help?
I have read that I would need to mod the cross member and the drive shaft for a TH400. I also read something about a switch for downshift on hard accel. Any help?
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
Likes: 384
From: South of giving a damn
St. Jude Donor '11, '17
No such thing as a free transmission. IMO, unless he bought this last week & never installed it the minimum effort will be to have it diassembled & checked for wear. Otherwise the free tranny might leave you stranded.
The 350 can be rebuilt for less than $500. After the checkup & extra parts & headaches from getting it installed, the free tranny might be the most expensive.
The 350 can be rebuilt for less than $500. After the checkup & extra parts & headaches from getting it installed, the free tranny might be the most expensive.
Pro
Joined: Nov 2004
Posts: 659
Likes: 0
From: Flower Mound Texas
I have a TH400 in my car now. My car is mostly a weekend driver but I'll drive it to work 5-6 times per month weather approving. The only issue I have with the 400 is terrible gas mileage because it only has three forward gears. Part of my problem is the big block, but the forum member who sold me my engine could get 15 mpg on the highway, and I get about 8. He was running a four speed std. But all that said, I don't think I'd pass up a free tranny but my money tree is picked clean.
Melting Slicks
Joined: Mar 2004
Posts: 3,472
Likes: 18
From: Lake Ozark, MO
I've been told several times (Forum included) that a 350 can be built strong enough for regular street / strip use. I have a big block and decided to have the 350 reworked in liu of the 400 purchase. Mine is a weekend driver to.....it would most likely be cheaper to rebuild by the tiume you change cross members, cables and such. As a $ reference, my local shop will do the rebuild with heavier sprag, clutches and shift kit for 425.00
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
If you go to the 400 you loose about 35 horse. The 350 can be built into a great transmission by any tranny shop. While the 400 is stronger is eats up about 35 more horse then the 350.
Rebuild the 350. With a shift kit it can give great shifts and will hold up to your power level.
Rebuild the 350. With a shift kit it can give great shifts and will hold up to your power level.
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Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
The weakest link in a TH350 is the sprag clutch. You can buy a heavy duty outer race from B&M, TCI, etc. for not too much money. Its good insurance if your going to make much Hp. If the sprag clutch grenades inside the tranny, it usually destroyes the housing along the way 
. With a good set of clutchs, and a heavy duty sprag, you'll probably be in good shape.
I've been running one behind a big block at the drag strip for years without a problem (Note: I don't use slicks so I do get some tire slip which reduces the shock on the tranny).
. With a good set of clutchs, and a heavy duty sprag, you'll probably be in good shape. I've been running one behind a big block at the drag strip for years without a problem (Note: I don't use slicks so I do get some tire slip which reduces the shock on the tranny).
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
The Turbo 350 is a fine transmission. Your car will be quicker with the 350. It consumes less HP and it has a slightly better first gear. The 350 can be made very strong. Wayne Nelson uses a 350 in his L88 clone. This is a 650 HP race car. One of the secrets to making them live on the street is to have good cooling.
BigBlockk
Later.....
BigBlockk
Later.....
Melting Slicks
Joined: Jul 2005
Posts: 2,545
Likes: 3
From: 406ci SB, AFR 180 Heads - 490 HP @5,600 RPM 529 lb-ft @ 4,100 RPM
I have the TH350 in my 79. I had it rebuilt with a 2400 stall, shift kit. My L-82 was also rebuilt at the same time to 375hp, and I like the set up, and have no issues with the TH350. I also just change my rear end gears to 3.55, as I had installed 4.56's but they were a bit much.
Racer
Joined: Sep 2005
Posts: 453
Likes: 1
From: Austin TX
What sort of shift kit would you recommend on a TH350 that shifts good and positive but does NOT bang the gears and ujoints? I have a highly modified tranny in my truck and it bangs unforgivably. Do different horse power levels require different shift kits?
P.S. - Thought I'd add a little to the thread instead of starting a new one.
P.S. - Thought I'd add a little to the thread instead of starting a new one.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
Originally Posted by blctalon
What sort of shift kit would you recommend on a TH350 that shifts good and positive but does NOT bang the gears and ujoints? I have a highly modified tranny in my truck and it bangs unforgivably. Do different horse power levels require different shift kits?
P.S. - Thought I'd add a little to the thread instead of starting a new one.
P.S. - Thought I'd add a little to the thread instead of starting a new one.
B&M has a great book on modifications and rebuild instructions for the TH350. One trick to help them handle extra power is to machine down the pistons and add addition friction plates to increase holding strength of the clutchs. GER sells this reduced hieght piston so you don't have to necessarily machine the original. There's also high strength input shafts, light weight drums, etc. made for these tranny's. TCI is an excellent place to find a whole range of goodies.
