700R4 Failure
 

I need your help.

The 700r4 in my truck failed after about 8,000 miles. I lost 3rd and 4th gear, so I am assuming that the clutch pack is shot.

What I am trying to figure out is why did it fail so quickly?


I have three theories:

1. improperly adjusted tv cable

2. at somewhere between 400-500hp it may be too much motor

3. improperly wired tcc solenoid - my reason for this is that when I bought the transmission the guy that rebuilt it swore up and down that it only needed to be connected to a keyed 12v source. Saying that no switches were necessary and the transmission would unlock on it's own. Everything on the internet says contrary, but he has been building for transmissions for a long time.

So what do you guys think?
What is your opinion on the tcc solenoid?
And lastly at 8,000 miles do you think I need to replace the torque converter when I rebuild the transmission?

-Thanks

Re: 700R4 Failure
 

i think you should go with another trand mission the 700r4 never been a strong trans mission with 4-500 hp you should look at a th400 or a 4l80e

Re: 700R4 Failure
 

I'm going to give the 700r4 one more chance. I am putting in a beast sunshell, tci servo, tci shift kit, 8 disk clutch pack, and a deep pan. I think with these upgrades it will have a fighting chance.

Re: 700R4 Failure
 

To say that a 700R4 is not a strong transmission is like saying that a chevy 350 is not a strong motor. You can buils a chevy 350 motor to make 150 HP or 600+HP . A stock 700 should handle 300-400 HP when installed correctly. On most stock 700 models the stock 3rd and 4th gears are the week point. I used the ceramic disk pack for these gears. The kit that I purchased had additional disks as well. This ceramic pack with extra friction disks makes a much stronger transmission. I also purchased a non electronic converter $99 at the local Daco Trans supply shop.

You also need to purchase the correct TV cable bracket that bolts to your carb.- i bought mine at Summit. ($40-50) thats the only way to adjust the shift properly. you will burn it up otherwise. if you are staying electronic lock up you need to buy a converter for that as well.

There is also a 28 spline and a 30 spline 700R4. i belive the smaller one was used on the V6 GM cars. I have been told that you can build this Transmission to handle Higher HP too.

Keep the 700- you will love the 4th gear when you are cruising at 70 and turning 2200 RPMs. I would not have anything else.

Re: 700R4 Failure
 

checkout http://bowtieoverdrives.com they drag race them as well as street them couple of buddies use them i think they can help. keep the 700

good luck
Matt

Re: 700R4 Failure
 

So with a non electric converter do you still need a 12v input? or is the trans complete mechanical?

Re: 700R4 Failure
 

I would like to figure out if mine is wired correctly so I don't burn out the new trans and to figure out if my converter is still any good.

Re: 700R4 Failure
 

A non-functioning TCC will not cause the 3-4 clutches to fail. It will cause a lube curcuit problem when in 4th gear.
The top 4 reasons 3-4 clutches burn...
1. Low fluid level.
2. Low fluid level.
3. Low line pressure/rise....See #1 & #2 or TV misadjusted.
4. More HP/Torque than the clutches can handle.

You can make it lock-up with just a B+ going to the TCC solenoid with a pressure switch grounding when the trans shifts to 3rd/4th gear. But i highly recommend running the B+ through a "duel" brake switch to kill power when the brakes are applied.

Deep pans are worthless in my opinion....They kill more transmission than they save. If you insist on having one MAKE SURE it comes with a filter extension. Seems everytime I pull a Aftermarket deep pan...The filter is laying in the pan.

For anyone running a nonlock-up converter.....The lube curcuit needs to be modified with a "lube Valve/Plug" in the pump.

Re: 700R4 Failure
 

I would save the cash and build a th350 or th400. The only overdrive worth bothering with if your making any real power is a 4l80e. The 700r4 is a weak unit. You can dump a ton of cash into them and still end up with a trashed unit. They will not live in a heavy truck with a bunch of power. Its that simple. The overdrive clutches especially are weak due to there size. They are tiny. If you burned the 3-4 clutches its likely the converter has entirely too much trash in it to stick it in another unit. I wouldnt risk it. It doesnt take much debris to make a valve stick or tear up the friction surfaces. If I were in your shoes I would go to the junkyard and grab a 4l80 core. Buy a decent converter. Get an upgraded sprag and have it rebuilt. It will hold your power level with 0 issues for a very long time. The only issue is making it work. You can buy a standalone electronic controller or convert it to a full manual valve body. You can either buy a complete valve body or buy the trans-go conversion kit. The trans-go kit is the cheapest option.

Re: 700R4 Failure
 

one other killer for 3-4 clutches that ALOT of builders miss is the input drum leaking between the input shaft and the drum especially hot but if you made it 8000 miles i would be checking the band servo for leaks at the case and the input drum for leaks if you made it 8000 then tv pressure was atleast close

Re: 700R4 Failure
 

I'm bringing this thread back to life as I have a 1987 700r4 that just failed with only about a 1000 miles since rebuild. It won't shift into 3rd or 4th gear. Best I can tell, the TV cable is correctly set and it wasn't low on fluid.

It is a 4x4 and I don't have the wires on the np208 transfer case hooked up. I thought they were just for the indicator light, but I also read somewhere that they send a message to the computor for the torque converter when you are in 4 wheel drive. Is there any truth to this? I had been driving around in 4wd the day it failed.
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Re: 700R4 Failure
 

i would say if youre sure you adjusted the tv cable properly and clutch clearances are right than while it apart check and see 1 if the case leaks at the servo bore and 2 see if the input drum leaks at the input shaft. it leaks where the end play washer sits you need to build up drum and fill the area where the bearing is with fluid to check find alot leaking and alll have the 3-4 clutches burnt

Re: 700R4 Failure
 

My TV cable pulls all the way out when the throttle is fully pressed. There is no slack in the TV cable at full throttle. I also checked to make sure the throttle is all the way open when the gas peddle is to the floor. Is there any thing I'm missing with respect to the TV cable?

When I first got the truck running I had two computers and accidently used the wrong one. I had a computer from a 3/4 ton Suburban with a TH400. I drove it to work once like this about 30 miles each way. I probable drove it no more than 100 miles like this. Could that have burned up the transmission?

I am just curious if I did something to cause this or it was a crappy rebuild.
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Re: 700R4 Failure
 

The TV can still be off....Especially if the TV spring itself is too short for your application, This is the reason you should always install a pressure gauge BEFORE its ever driven.

Watch for Instant pressure rise when pulling the TV cable, Ideally you want a 1-2 psi preload on the cable above baseline (TV unhooked)......Ask the builder to omit the TV exhaust check ball so baseline pressure is easy to obtain.

As Jfortvalley mentioned....The Input drum HAS to be air checked for leakage around the input shaft, Test the 3-4, Forward & Overrun, Not just the 3-4's.

The aluminum 3-4 piston can crack, Though it is rare. I use the Bonded steel 4L60E 3-4 & Forward pistons on just about every build.

Just for sake of explaining....The back side of the 2nd servo is used as the 3rd clutch accumulator Thus the reason for checking the servo area.
Replace the 3rd clutch accumulator capsulated check ball 100%!
Replace the Input drum capsulated check ball as well, Or install an orifice in its place (Transgo)