TH350 vs. 700R4
Thread Starter
Instructor
Joined: Jan 2012
Posts: 156
Likes: 0
From: Mount Sinai New York
TH350 vs. 700R4
I know a lot of you guys have switched from the 350 to the 700. My question is the 700 a inherently stronger unit that the 350? I'm installing a small block thats north of 500hp, and I don't want to have any durability issues. My transmission guy wants to charge me about $600.00 to beef up my TH350 with a custom stall converter. But wait, it gets better! I found someone local to me who has TWO 700R4 units from an IROC. Just hung up the phone, he wants $200.00 each, or he'll sell them both for $300.00.
Any and all opinions are welcome, thanks.....Vince
Any and all opinions are welcome, thanks.....Vince
Pro
Joined: Aug 2005
Posts: 613
Likes: 2
From: West Central Florida
Just my opiniion here... I switched from a th350 to a 200-4r.
The 700r4 was too much modification for my already modified (and very tight) vette.
First, I'd like to say, NOTHING feels like the th350 in a hot rod.
Mine had rock hard tire blowing shifts in each gear, till a hard trip up the on-ramp to the interstate took it out. When a pump goes, its over.
700r4 pros: 1- great first gear if you dont have a steep rear gear. Good gear ratios for driving around town. 2- Has overdrive. Wont necessarily get "better" gas mileage though. 3- can be built for over 500hp, but needs some mods to hold up to track abuse.
700r4 cons: 1- Soft shifts, you can get first to hit pretty hard but 2nd and up are going to be mushy. (not as crisp or tunable as the th350).
2- TV cable has to be right and kept right, or say good-bye. 3- Very heavy and very large compared to the th350. May need to modify your tunnel or floors and your crossmember. 4- Different length. Have to shorten your driveshaft, but the th350 yoke should fit. 5- Must be kept cool.
The 700r4 was too much modification for my already modified (and very tight) vette.
First, I'd like to say, NOTHING feels like the th350 in a hot rod.
Mine had rock hard tire blowing shifts in each gear, till a hard trip up the on-ramp to the interstate took it out. When a pump goes, its over.
700r4 pros: 1- great first gear if you dont have a steep rear gear. Good gear ratios for driving around town. 2- Has overdrive. Wont necessarily get "better" gas mileage though. 3- can be built for over 500hp, but needs some mods to hold up to track abuse.
700r4 cons: 1- Soft shifts, you can get first to hit pretty hard but 2nd and up are going to be mushy. (not as crisp or tunable as the th350).
2- TV cable has to be right and kept right, or say good-bye. 3- Very heavy and very large compared to the th350. May need to modify your tunnel or floors and your crossmember. 4- Different length. Have to shorten your driveshaft, but the th350 yoke should fit. 5- Must be kept cool.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
Just the opposite. A TH350 is a tough transmission that will survive some pretty serious power.
With the 700, you hear about a lot failures in high hp applications unless someone spent quite a bit on a "best of everything" build.
With the 700, you hear about a lot failures in high hp applications unless someone spent quite a bit on a "best of everything" build.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
700r4 cons: 1- Soft shifts, you can get first to hit pretty hard but 2nd and up are going to be mushy. (not as crisp or tunable as the th350).
2- TV cable has to be right and kept right, or say good-bye. 3- Very heavy and very large compared to the th350. May need to modify your tunnel or floors and your crossmember. 4- Different length. Have to shorten your driveshaft, but the th350 yoke should fit. 5- Must be kept cool.
2- TV cable has to be right and kept right, or say good-bye. 3- Very heavy and very large compared to the th350. May need to modify your tunnel or floors and your crossmember. 4- Different length. Have to shorten your driveshaft, but the th350 yoke should fit. 5- Must be kept cool.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Depends on your application. If mostly a drag car, then I'd stay TH350. If mostly a street/highway cruiser, then 700R4 all the way. The lock up od, is the cats meow on the highway. Like anything, there's different versions, with later SUV/police units being stronger. As mentioned, the CV cable can be a real pain, and maybe consider going with a later still 4L60E version, and after market computer module.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Neither a stock TH-350, TH-200-4R nor a TH-700R4 will support 500hp and associated torque as originally built. I think that only the TH-400 could handle that power with the original factory configuration for the Corvette.
But, any of the GM auto transmissions can handle that kind of power, if they are assembled with the required 'beefier' parts. And, most tranny rebuilding operations know what those parts need to be. The converter must be capable of withstanding that kind of load, as well.
Pick whichever design unit you wish to use (if you want overdrive, select a 200-4R or 700R4); if not, stay with a 350.
I highly recommed the advantages of an overdrive unit, if you drive at highway speeds for any significant amount of time. This is particularly beneficial if you have 3.55 or higher rear axle ratios.
But, any of the GM auto transmissions can handle that kind of power, if they are assembled with the required 'beefier' parts. And, most tranny rebuilding operations know what those parts need to be. The converter must be capable of withstanding that kind of load, as well.
Pick whichever design unit you wish to use (if you want overdrive, select a 200-4R or 700R4); if not, stay with a 350.
I highly recommed the advantages of an overdrive unit, if you drive at highway speeds for any significant amount of time. This is particularly beneficial if you have 3.55 or higher rear axle ratios.
Instructor
Joined: Dec 2011
Posts: 142
Likes: 0
From: Tucson Az
Had a custom built 700r4 behind my 500hp 406" in a 3700lb car it held the power just fine... BUT mine had a manual reverse valve body,TCI internals,30 spline input,red alto clutches,kevlar band etc,etc. You dont need a manual valve body but if you dont mind shifting up and down all the time it eliminates the need for the TV system, Bowtie Overdrives has a nice TV cable setup and Ive installed several 700's from Phoenix transmission with thier supplied TV systems without any issues. Th350's can handle the power also my 3400lb camaro had one it ran 10.30's with a 625hp bbc it was built with just a manual valve body and a Fram rebuild kit.
Advanced
Joined: Apr 2008
Posts: 92
Likes: 1
From: Carol Stream Illinois
700R4 all the way! Go with the later year though as it has 30 splines compared to the earlier versions which are weaker with 27 splines. Great gear ratio in first! have mine behind a 430HP 383 stroker with no issues. They are stronger than most want to admit. Good luck with your decision!
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Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
That cant be said for the other 2.
After rethinking, the 350 could use a new hardened race for the intermediate sprag, but thats less that $50.
Last edited by DRIVESHAFT; Mar 2, 2012 at 02:27 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
I believe that a 'stock' THM-350 unit is not designed to handle that kind of power. Yours may have held up. But, suggesting that all of them will...because yours did...is not doing a good service for other Forum members.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
And I didnt say they couldnt use some mods at that power lever. I said that the hard parts would hold up.
A TH350 built for 500 hp is a pretty economical transmission. The same cant be said for the 700R4 or 200-4R
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
I think you'll find a lot of folks who kept their TH-350's in the car after they beefed-up the engine....and it didn't last all that long, too.
The 700's get a bad rap; but many times it's because the owner didn't really set up the TV cable correctly and the line pressures are low at WOT throttle. It just burns up the clutches...quickly!
Folks can do what they want. But, I wouldn't put a stock configuration 350 behind 500 hp. Just sayin'....
The 700's get a bad rap; but many times it's because the owner didn't really set up the TV cable correctly and the line pressures are low at WOT throttle. It just burns up the clutches...quickly!
Folks can do what they want. But, I wouldn't put a stock configuration 350 behind 500 hp. Just sayin'....
Burning Brakes
Joined: May 2009
Posts: 1,232
Likes: 6
From: Tucson AZ
St. Jude Donor '12
A well built 700r4 will feel nice behind that beefy motor. I have a BTO 765r4 & crossmember in mine, Even with a small 3000 rpm converter, I still get lockup & low rpms at highway speeds - best of both worlds.
I can't say enough nice things about BTO.
I can't say enough nice things about BTO.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Hey "neighbor", Ive had a few 700's and a 4L60E (same thing just from the mid 90s). Its ok in stock form in stock applications, and can be built for abuse.
With that said, someone else mentioned the 2004r, and in my opinion that is the hot ticket. Closer ratio between 1st and 2nd, so its not a radical drop off between gears, and you get your overdrive.
A friend of mine in Kings Park has a 1986 Monte with a stout 406 that runs mid 10s on the bottle. Behind it is a 2004r built by Freddy Brown.
While I know that FB is still a big name in these parts, as is Select, you may want to check on the Turbo Buick forum, as I know there are 2 other big names here on the island, I believe one of them is "CK".
The more research you do, the more you may start to lean toward the 200.
With that said, someone else mentioned the 2004r, and in my opinion that is the hot ticket. Closer ratio between 1st and 2nd, so its not a radical drop off between gears, and you get your overdrive.
A friend of mine in Kings Park has a 1986 Monte with a stout 406 that runs mid 10s on the bottle. Behind it is a 2004r built by Freddy Brown.
While I know that FB is still a big name in these parts, as is Select, you may want to check on the Turbo Buick forum, as I know there are 2 other big names here on the island, I believe one of them is "CK".
The more research you do, the more you may start to lean toward the 200.
Thread Starter
Instructor
Joined: Jan 2012
Posts: 156
Likes: 0
From: Mount Sinai New York
This turned out to be an awesome thread for me. After agonizing over the 350 and 700, going to take the advice of BigBlockDave and others, and go for the 200.One of the reasons is that the new 355 going into the car is WELL north of 500hp. Unfortunately I'm putting the engine in with the stock TH350, because my paint guy needs the car to be mobile. The upside is I have a little time before the summer to get a trans built.
I wanted to attach some pics of the new engine, but for some reason I can't post attachments, anyone know why? thanks
I wanted to attach some pics of the new engine, but for some reason I can't post attachments, anyone know why? thanks
Race Director
Joined: Apr 2007
Posts: 14,062
Likes: 602
From: Henderson Nv-Rohnert Park/Sonoma C o. ca/born in NY Rockaway Beach.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
trans choices are certainly up to the individual.....but take this into consideration almost every hot rod you read about uses a 700r4 or a th350 and these are big dollar projects......
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Bob, the 700 does get used widely, but the 200 is a nice swap for the 350...its the same length, and uses the same yoke: driveshaft remains the same.
There are some wicked turbo buicks out there running some insane numbers and killer 60ft times...that 2004r can take some abuse when prepared for it.
There are some wicked turbo buicks out there running some insane numbers and killer 60ft times...that 2004r can take some abuse when prepared for it.
Race Director
Joined: Apr 2007
Posts: 14,062
Likes: 602
From: Henderson Nv-Rohnert Park/Sonoma C o. ca/born in NY Rockaway Beach.
Bob, the 700 does get used widely, but the 200 is a nice swap for the 350...its the same length, and uses the same yoke: driveshaft remains the same.
There are some wicked turbo buicks out there running some insane numbers and killer 60ft times...that 2004r can take some abuse when prepared for it.
There are some wicked turbo buicks out there running some insane numbers and killer 60ft times...that 2004r can take some abuse when prepared for it.
Still curious on the HP gain from using the 200r from the 350 ? ?
anyone know if the extra hp is true and about what gain will yo see.... ? ?