Th400 Or 700r4

[eightbanger]

Took my truck on it's first long journey the other day 4 hr round trip most of it on the freeway and she took it in her stride It's running a 454 mated to a TH400 which has been tweaked by the po (see sig) and all the while I was wishing I had a 4th gear...cause driving at a steady 75mph the engine was really reving high, had the radio up real loud just to hear it there was a lot more to go on the gas pedal but if I took it passed 80 mph they would have heard it in Scotland. My question is this, would swaping out the 3 speed auto TH400 for that 700R4 that everyone seems to be going for solve this? is my engine reving that high at speeds cause it needs a 4th gear. Then i'm thinking is there a down side to having a 4 speed? like losing the power that I have now just running around at lower speeds. Or is there a better trany out there that would give me the best of both worlds? any help or sugestions are appreciated.

[Ol'Rover]

TCI 700R4, They handle 454's nicley, my uncle has one in his 56 Bel-Air, bought a crate 454 and he said he's pushin out about 450+ horsepower. He had a TH400 onit befor, and when he changed over to the 700 he noticed a big difference, put more power to the ground quicker, and way better cruising he said.

[leddzepp]

I have 700r4 and love it. It actually has a very low 1st gear, so you have a great holeshot at traffic lights. If you are worried about losing any power at higher speeds, keep the overdrive off. I do not know about any other automatics in these trucks, but I do like the 700r4.

[Rollie396]

You could check out a gear vendors overdrive unit?I don't know a whole lot about them,but a fella I know has one behind a real nasty 468/T400 combo and he loves it.

[eightbanger]

I'm not very mechanicly minded so when you guys talk about overdrive is that 4th gear or what? Leddzepp what do you mean when you say keep the overdrive off?. Rollie do you have any other info on that overdrive unit you mentioned?

[haysonj]

I have the gear vendors with a turbo 400 and I love it It's like having a six speed and really helps with the towing. the stock ones are good up to around 1200 HP but they are pricey I paid $3300 for mine.

[Rollie396]

Here's their site...they are a little pricey,but I think it may be worth it.

http://www.gearvendors.com/custom.html

[Ol'Rover]

got a normal GM 700R4 in my 88, and it also has a realy nice low 1st gear, as said...great for getting the holeshot at stop lights lol

[eightbanger]

Thanks Rollie

Now I need to decide between the two, that may be down to price...and how easy are any of these options to fit? I mean is this a leave into the shop job or a DIY thing??

[jayharrell]

Do you have to have some control modual for the 700?? isn't it computer controlled?? *know nothing about the r4 other then its a 4 speed.

[Ol'Rover]

The 700R4 is all mechanical and hydraulic. You are thinking of the 4L60E the electronic version of the 700R4

[haysonj]

The 700R4 is not a good trans for a heavy truck especially if you are towing or racing. also they have to be set up exactly right or they won't last. The gear vendors is a direct bolt on and all you have to do is shorten the drive shaft. Only took me two hours to install and had my drive shaft back that afternoon and was on the road. Very simple

[Rollie396]

haysonj,how was the electrical part of the install?Fairly simple?Looks like it may take a bit of getting used to using it?

[eightbanger]

Yeah its' a shame the copperhead video doesn't show more of the install especially the electrics, I had no idea about this gear vendors thing it really looks like the way to go pricey but a lot simpler on the install and to be fair Bowtie Overdrives do state that if you want that bit more then gear vendors or there own 4l80E is what you will need.

[haysonj]

The electronics are simple you just mount the controls and they plug in It has a speed sensor that goes in the speedo cable for the automatic operation. I have the B&M Mega shifter and they sold me the handle with the shift button like they did in copperhead. You can shift it off and on between gears so it acts like a six speed. I usually leave it on and it shifts by speed usually only three gears but if I hit a grade I turn it off and it drops to the normal 1 to 1 gear.

[Vince M]

The selection of the 700r4 is great if you have the right gear ratio in the rear end. It sounds like you have a 3.73:1 ratio which the 700r4 will work great with. You can even go to a 4.10:1 and it will work great. If you have a 3.08:1 the fourth gear will drop the enginge revs too low at freeway speeds.
With a lockup you can keep the transmission oil heat down and even gain a few hundred rpms of more overdrive.
With the right mounting the 700r4 will bolt right into the same location as the TH400. You want a tail section that has the mount on it. This gives you pan clearance with the crossmember and it will use the same tranny mount and crossmember as a Th400.
I put two 700r4's in now and with the right stuff it works great.
With a 3.73:1, a 700r4 and 30" diameter rear tires I was doing 1800 rpm at 70 mph in lockup. You won't need to turn the radio up anymore to drown out the motor.