Should I bother with another 700R ?

[72MARIO]

I am on my 2nd 700R and wondering if I should just get a 350 or 400 built rather than blowing up these 700Rs. I have all the correct line pressure settings and brakets.

My main concern would be the RPMs I am going to turn with a 350 or 400 3:73 gears and 275 60 15 rire. Would it be alot more ?

Just looking for opnions.......

[Custom 68]

Man I would think you should be able to get a 700 to live...They are not the strongest as you and everybody knows but it doesnt look like you are asking for too much with your setup? I would question your previous 700's
Dave
If you are planning on driving this much I would stick with the OD...

[67ChevyRedneck]

You've blown up a second one??? I remember the pics from the first one... gruesome

It would be 30% higher at highway speeds in 4th gear. The 700R4 has a 0.7:1 final drive ratio which equates to a 30% gear reduction. The 350 and 400 have a 1:1 final drive ratio. Basically if you're turing around 2300rpms @ 75mph (which is what my truck runs 350/700R4/3.73) then with a 350 or 400 you'd be turing about 3K rpms.

I've killed a 700R4 as well. If the next one blows "untimely" I'm swapping for an NV4500 if I can even find one! To ensure long life of my next tranny I'm going with an external cooler, Bowtie overdrives TV made EZ kit and lock up kit.

[ratrod67]

I went through 3 of 'em behind a 425 hp small block. I gave up.

[cwilkie]

I am having doubts about mine as well. At 65mph I am at 2400 RPMS. I think I should be at a much lower RPM than that. I have a 396BB with a 3.07 rearend. Also the it seems to shift from 1st to 2nd really fast. The T.V. cable is set and I even took off the pan the make sure it's set a wide open throttle. Think it would be the governor? I have a lightweight governor in there right now. Do you guys think putting a heavier one in will help?

[67ChevyRedneck]

Originally Posted by cwilkie

I am having doubts about mine as well. At 65mph I am at 2400 RPMS. I think I should be at a much lower RPM than that. I have a 396BB with a 3.07 rearend. Also the it seems to shift from 1st to 2nd really fast. The T.V. cable is set and I even took off the pan the make sure it's set a wide open throttle. Think it would be the governor? I have a lightweight governor in there right now. Do you guys think putting a heavier one in will help?

Something isn't quite right. Are you sure your tach or speedo is correct? I have a 3.73 rear and at 65 my truck is turning right about 2 grand. With the 3.07 your truck should be turning like 17 or 1800 rpm at that speed. The 3.07 also may be too high of a gear for a 700R4 (even new full size trucks with OD only come with a 3.42 as the highest gear) With gearing that high I'd definately leave your truck in 3rd when driving around town and leave it in 3rd until you at least hit 50 on the highway. How does it fell on the highway? Does it feel sluggish and underpowered?

[SB406]

cwilkie-
Sounds like your converter might not be locking up. Be careful because a 700r4 doesn't route fluid to the cooler until the converter locks. Check this out for a good article on converter lockup logic:
http://diy-efi.org/gmecm/papers/tcc.txt

72Mario-
wanna see what R's you'd be turning- Put it in 3rd gear & drive around a while. 3rd is 1:1 in a 700R like 3rd in a TH400 or 350. The preferred trans is the 4L80E which is basically a TH400 with overdrive. However, in order to run it you need a computer & wiring harness or a very costly adapter harness.

I've had a 700R behind my 406 for about 60k miles & don't have any complaints. 2nd gear is the weak link so I put in a corvette servo to boost the 2nd gear apply band holding pressure. Nice firm 1-2 shift for about $25. No shift kit in mine because they usually last about 20K in the 700r4's before stuff gets hammered and it shifts like crap.
Granted, I know that a 700R isn't the strongest slosh-box around, so I keep that in mind while driving. However, the life of any tranny is a function of how you drive it. No transmission is going to like neutral drops, brake torques, and flooring it off the line at every light. I'm not saying that your driving habits puked the tranny, but if you want to kick the hell out of it, I'd put in the TH400 or 4l80e. If you want to cruise- 700R4.

[SB406]

My 88 chevy van had a 700R4 & 3.08's.

[67ChevyRedneck]

Originally Posted by SB406

My 88 chevy van had a 700R4 & 3.08's.

It's been hashed out on here several times that a 3.08 or 3.07, or whatever it is, is a tick on the high side for these trucks. Not to say it isn't done, nor is it wrong, but the "general consensus" that with a 350/700R4 the best gearing for these particular trucks is a 3.40's something or a 3.73

[incoma]

wheel diameter will also greatly impact the rpms an engine is running. I don't have the link with me right now, but there's a website that you can use that will calc rpm based on axle gear, transmission gear, and tire/wheel height. I think the math is pretty accurate. I used it to calc my current setup, and my future setup. It was pretty handy to figure out what pieces I could install now and keep with my future setup.

[cdowns]

www.fbperformance.com go with thier 4STB prostreet tranny no tvcable no lockup bull full manual shift just about bullitproof to 900HP

[LUV2XCLR8]

Man oh man, you guys are scaring me, I looked at a New one for
around $1600 that was rated up to 650 hp, but now I'm un sure.

[kafn8d]

I recently put in a 700r4 from Bowtie and it is turning aroung 1500 rpms at 65 mph. I have 3.08 rearend and 275/45 20's all around. Speedo gears were ordered and they appear to be working right.

[powell72]

kafn8d, 1500rpm is too low for a 700R4 to be running in OD. They need to be at least around 2000rpm. I just don't want to see you kill yours.

[the70chev]

I made a similar mistake by putting a TH350 which is about the same strength as a 700R4 behind my Mildly built Big Block and it gave up so I found a 400TH, much better to hell with OD unless you use it to travel long distances on the Highway

[68Stepbed]

My truck with a 350/TH350 and 3.73 combo turned exactly 3200 rpm at 70 mph. Ya'll are startin to worry me about going overdrive now. Check these guys out.

[gator2511]

I have a 72 K10 with a 3.73 hooked to a TH400 through a G.V. OD tranny and I turn 2100rpms at 75 mph. I like the combination for strenght and lower rpms. When I'm in the woods I just turn the OD off.

[Already Gone]

Originally Posted by 72MARIO

I am on my 2nd 700R and wondering if I should just get a 350 or 400 built rather than blowing up these 700Rs. I have all the correct line pressure settings and brakets.

My main concern would be the RPMs I am going to turn with a 350 or 400 3:73 gears and 275 60 15 rire. Would it be alot more ?

Just looking for opnions.......

Your tires are the same height as my 235/70R15's and I run a BB with 3:73's and a TH400 and at 60MPH/ 100KMPH I'm doing 2900 RPM.. I have a 700R4 in the garage ready to go in my truck and have been having second thoughts after readfing threads on here and talking to local guys that have done the swap.. Dont know about you in Ontario but our gas jumped to 119.9 a litre yesterday..

[72MARIO]

Gas is still 108 here. I drove the truck daily in the summer. I like to open up the truck after a hard day at work. So I kinda beat on it. Never off the line just a few WOT shifts. But I dont think I have ever got a really good 700R built for me yet.

I have a 350 here and money is way too tight to pay 1600-2000 for a well built one so it might make it's way in (getting married and home ownership)....... would'nt it be cool if my MPG gets better with a good working tranny ?

[SB406]

3.42 rear gears + 255/70R15 tires + 700R4 + TBI 406 = 1650RPM @ 65MPH, 1200RPM @ 45MPH, 16MPG City/21MPG hwy.

[cwilkie]

After a little brainstorming I found out at an actual speed of 65mph the odometer in my truck was reading 53mph. So when I was going an actual speed of 65mph the RPMs were at 1800. Which is awesome. No I just need to correct my speedo gears.

[Boog]

There are a number of tire, gear, tranny calculators available to calc what you may need. www.richmondgear.com/streetcalculators is only one. Easy to see how much rpm changes with taller tires or lower gears or plain 3 speed trannys or OD trannys.
What you are going through is exactly why I will not be running any OD trans in my 69. I want a simple T350 for mine. Currently has a 4.11 but will eventually move to a 3.08 gear. Good all around gear. Gas pricing is a major deciding factor even for an occasionally driven truck.

[russellmarling]

I destroyed 5 700r's behind a mild daily driven 406. Two of them were built and three of them were stock but they all sucked equally. I will never buy another one. Just my two cents.

[djracer]

I love 700's but I have broken a few over the years(I broke most of them with the wrong convertors). 72MARIO I wish you weren't so far away I could get you a nice 700 built!

[Robert1970C20rstbukt]

TH400 is the way to go!