TH350/400 vs 700r4

[Big_Block]

Hi i am currently working with a 350 small block chevy motor and I am considering building it to a 383 stroker in the near future, I was just wondering what Tranny i should go with that would be suite the 383 stroker the best. I heard the TH400 is the best tranny to go with but i just wanted some other opinions before i tire the knot on the deal. thanks!!!

[Classic Heartbeat]

I have yet to install a 700r4 tranny in any of my own trucks, so i do not have any personal experience on them. Just what my customers have told me or what I have read on this and my boards. I will be installing one in one of my projects soon because I like the reviews I have seen on them. However between the t-400 and t-350, I believe the t-400 is a bit over rated and also robs about 20% more horsepower than the t-350. The t-350 is a great transmission and are relatively innexpencive as a plus. They can be built to withstand just about anything you can throw at it and don't rob the kind of power that the t-400 does. WES www.ClassicHeartbeat.com

[COBALT]

I currently have a stock 350 (with heads and too-small 2bbl intake from a 327) bolted to a TH400. It's a wierd mix, but it actually performs surprisingly well. I'm very impressed with the TH400 so far. Yes, it's a bit more tranny to turn, but it's bullet proof. With a good rebuild + a good shift kit it will hold up to anything I want to throw at it. I'm thinking about going the same route as you, so I want a substantial driveline.

Also, for later if I decide to get a big block I won't have to go through this decision-making process again.

I think it really depends if you want to have an overdrive gear or not, and how much are you willing to spend to get it rebuilt or worked on in the future. TH350 and 400's are pretty basic, and they don't look to complicated. I"ve heard the 700-R4 can be a real *****.

[Longhorn Man]

Another option you have not mentioned here, you can get your TH350 or Th400 (I vote 350...you can build them to hold more power then you'll ever make) and then later on down the road, you can get a Gear Venders over/under drive. These things are tougher than that fruit cake you got last X-mas.
Here's the link if you are not familiar.
http://www.gearvendors.com/commercial.html

[72Blazerod]

I have a 1972 TH 350 sitting in my garage. I believed that they were weak trannies but after hearing what you guys said, maybe I'll rethink it. The th350 I have sitting aroung is from a 3/4t 2wd. What would I need to do to hook it up to my NP205 tranfer case? How hard are these to rebuild yourself? What kits are out there? I need it to be stout because I will be using it to tow a 16ft travel trailer all around the place. Any tips?

BTW, it is in my 1972 Blazer 4x4.

Rod

[fnoblitt]

i vote th350, i have one in mine.it was cheap to rebuild,i belive it will last me a long time.the 700r4 will cost a lot more to get going.and i don't like the way they shift out of first gear too soon. my dad has a th400 in his 67 c10 with 283 2bbl.he likes it.

[lukecp]

Well, i was seriously considering putting a 700r4 in place of the TH350 in my truck for quite some time. But, i rethought the economics of it. A good rebuilt TH350 runs around $400 in my area, with installation being about $75 extra. A rebuilt 700R4 is about $800, and the parts and labor to convert would proably be another $300. So $1100 vs. $475. With the overdrive, it would take me a very, very long time to save $625 in gas, if i only pick up 2-3 mpg. The TH350 has a reputation as a very strong tranny too. Mine is original to the truck, and has lasted through the original 350, the same 350 being rebuilt, and 10xxx miles on the rebuilt 350 i have in it now. It is just now starting to have problems, it slips a little bit on cold mornings, and takes a while to go into reverse. That should be about 210xxx miles, and 30 years of work. I have decided to put a TH350 with a 1900-2000rpm stall converter, and a RV shift kit in instead of a 700R4, and get another 200,xxx miles out of it.

[6869704X4]

Another thing to consider is the gear ratios. The 700 has a lower 1st gear than the 350 or 400. Probably why it shifts out of first so soon. But a lower 1st gear helps with the launch.

Blazerod,
Spline count on the out put shaft is one issue. And you cant use the 4x2 shaft because the adapter that connects the trannie and xfer case bolts up in place of the tailhousing. Unless you want to go with a divoced xfer case. Thats a whole nother deal.
The 700 is a popular 4x4 trannie because of the lower 1st gear. Better for crawling.

Whatever yall decide get the latest model 700 you can find or a beefed up rebuilt one. The early 700s were weak and they got a bad rep from that.
I got this info from a bud of mine who rebuilds trannies.

[mrein3]

yellow72custom beat me to my normal reply when this subject comes up. For towing my boat across the state of Minnesota I wanted to swap from my 3-speed manual to an automatic transmission. I tried REAL hard to make an arguement to use the 700r4 with overdrive but the facts remain. In my area I rebuilt a TH350 to withstand anything I could toss at it for $450. To do the same thing to a 700r4 would have cost at least $800 with one shop estimating a minimum of $1000. Not to mention the cost of a used Th350 is less. Then to top it off I do most of my towing with my truck which is STUPID to do with a 700 in overdrive so I'd only be gaining from the lock-up in the 3rd gear verses the non-lockup in the th350 which is less than 10%.

Just do the math. Guestimate a 30% increase in highway mileage with a 700 verses a th350. Take the price of gas and determine how many miles you have to drive to save the price difference. For me it was 60,000 miles of highway driving to make up the difference. I only drive 5000 miles per year and most of that is towing so I couldn't use OD anyways. The payback just isn't there.

Needless to say I went with the TH350.

One more thing...
No matter what you do auto tranny wise put in an external transmission cooler. I put a temp guage in my transmission when I installed it. I drove to a tournament WITHOUT the external cooler to get some data. The transmission fluid shot up to 240 degrees in stop-and-go traffic and stayed at 210 just going down the road. Same boat same trip one week later with the cooler and the tranny ran 150 to 185 driving down the road and NEVER went over 200 in stop-and-go.

[Longhorn Man]

For acceleration reasons, that deep first could actually hurt your E.T. As a member pointed out, the RPM drop from 1st to 2nd on the 700 is drastic, and very hard to keep the engine in its power band.

[Radiatta_71]

I was considering swapping out my th350 for a 700R4 in my Blazer now i'm starting to rethink this. Although i do like the lower first for 4wheeling and the over drive for the freeway. Advance adapters sells a kit which is only a output spline shaft for under $200 this is a lot cheaper then a conversion to a th400.

The real question is putting price aside. What will handle the best under a big block.
And what auto tranny is better for 4wheeling.

[6869704X4]

Originally posted by mrein3

One more thing...
No matter what you do auto tranny wise put in an external transmission cooler. I put a temp guage in my transmission when I installed it. I drove to a tournament WITHOUT the external cooler to get some data. The transmission fluid shot up to 240 degrees in stop-and-go traffic and stayed at 210 just going down the road. Same boat same trip one week later with the cooler and the tranny ran 150 to 185 driving down the road and NEVER went over 200 in stop-and-go.

What was the outside air temp during your trips and where is your temp sending unit? I mounted mine in the remote filter which is prior to the cooler. Ive been running about 200 deg here in Fla with air temps of about 90/95 or more. I also put an engine oil cooler/thermstat with temp sensor on the remote filter and its never been over 180.

[mrein3]

Outside air temps on the two trips were between 68 in the morning and 79 in the afternoon. Since that trip I pulled the same boat in 90 degrees with the similar temp readings.

I put the temperature sender in the transmission where a leaking pressure switch was located. To be perfect I should be measuring the fluid returning to the transmission but the temp in the tranny will be similar to the return fluid temp.

Also you guys down south probably route the external cooler AFTER the tank on the radiator. Up north here we put the external cooler BEFORE the radiator tank. Similar to running your tranny too hot you can wreck it by running it too cold. If the outside temp is -20F and I'm pulling my fish house across the lake I might see temps below 100F in the tranny fluid with the cooler AFTER the radiator. You DON'T want to do that. In some winter situations your radiator becomes a tranny WARMER.

An even better solution would be to install a thermostat and only run your tranny fluid through the cooler/warmer when necessary. I know one guy that does that. But then I know 100 guys who don't.

[6869704X4]

Im with ya on the too cold. Same for engine oil. Perma-cool has a lot of info about this on their web site.

[guypm]

My truck is not a daily driver. When I first bought it it had a TH350. The rear gear is 3:73. I have rebuilt most everything and transmission was changed out for a 700r4. I spent the money for the 700 and am glad i did. I love the low end out of the hole, yet when on the hiway at 70mph the rpm's are really much lower than with the th350. I didnt even consider the long run and how long it would take to pay for itself cause i have way overspent on this project anyway. This is my hobby and i am lucky enough to have a good wife that puts up with it. I think if i were to race or pull stuff with it, i might have stayed with the 350. Like i said, i love my combination. I had a 1650 stall converter put in and a small shift kit also. We also upgraded to stronger transmission guts while we were at it.
Hope this helps,
Guy
P.S. Just brought mine to the paint shop 7-5-02. I'll post pics when done with paint

[mikep]

I used to be REAL hard on transmissions. Lots of hi stall converters, Hi RPM power braking, FULL THROTTLE ALL THE TIME kind of stuff behind big blocks, hi rpm small blocks and the like both on the drag strip and on the street driving like I was on the drag strip with 11 and 12 second cars. I have broken several turbo 350's to the point of gears through the case, pans full of metal sludge etc. I have NEVER broken a turbo 400.
realistically it probably takes another 10 HP to power one. I think its worth it.

[breeh]

I am running this in front of a 700R4 and wouldn't trade it for a dozen TH350/TH400's. I am going to put this motor in my 4x4 as I am building a 2nd 427 for my car (I learned a few things).