700R4 Troubles

workinprogress

Member
Joined
Jun 23, 2007
Location
Statesville,NC
I was wondering if any of ya'll had any ideas on what to do about my transmission problems. I have a 85 K5 with 350 followed by a 700R4 trans. It started out holding in the gears not wanting to change and eventually quit working. Felt like it was stuck in a high gear. I drained fluid and replaced filter and it started working again. Well it started holding gears again and went out on me again!! It probably only worked for 200 miles or so. The blazer is on 38's and has stock gearing (yes I know I need to upgrade but this is a budget blazer). Any suggestions??!!
 
workinprogress said:
The blazer is on 38's and has stock gearing
Click to expand...


Its toast...the 700s get abused especially on this board and I still defend them like crazy, however they require some love...and this combo....bad
 
workinprogress said:
I don't know what the TV cable is...
Any suggestions?
Click to expand...


ouch...
The 700 does not have a kick down cable it has a TV cable that is critical to proper pressure regulation internally.
If you dont know what it is, and you have ever messed with the carb there is a better than average chance that it is not hooked up or out of adjustment.

if so....that is another toasting event.

As for suggestion, I am guessing based on your assessment that it is time for a rebuild.
make sure the TV is reinstalled properly and I wouldnt waste my time rebuilldig a 700 and putting it back in front of 38 with 3.08 gears

I would re gear at the same time.
 
The TV cable is called the detent cable, or kickdown cable. It's job is to command the trans to downshift when a certain throttle position is reached.

The amount of slippage required to turn 38's with, at best, 4.10 gears (but likely 3.42's or 3.73's) has created an incredible amount of heat and stress on the entire truck, motor included. It's STRONGLY advised that you regear before even focusing on the transmission. Otherwise, you'll be right back with the same problem.
 
maulcruiser said:
The TV cable is called the detent cable, or kickdown cable. It's job is to command the trans to downshift when a certain throttle position is reached.
The amount of slippage required to turn 38's with, at best, 4.10 gears (but likely 3.42's or 3.73's) has created an incredible amount of heat and stress on the entire truck, motor included. It's STRONGLY advised that you regear before even focusing on the transmission. Otherwise, you'll be right back with the same problem.
Click to expand...


The TV cable in a 700 does alot more than just the detents/kickdowns. It sets the line pressure and controls the changes in line pressure for shifting as well as the keeping the torque from being applied to the clutches at all times. If it was driven on without being setup correctly, for any lenth of time ( as you said 200 miles) that tranny is toast just as SkyHiK5 said. You definitely need to regear with 3.08's and 38's. All the extra strain of the big tires is being put on the tranny, this is why you need to re-gear the axles badly. Doing so would take a great deal of stress off the engine/tranny and would pay for itself in the long run with saving money from being spent on transmissions.
 
yup- its a gonner. I cooked one when I did my 6.0 swap and it turns out I was just .2" off on the swing of the bellcrank and it died in like 20 miles. I downloaded the setup instructions from TCI and did it right the second time, the first time I tried to copy the throttle body dimensions and I killed it. but I am running 4.56's on 38's and need to go to 4.88 or deeper.
 
if I was rebuilding a 700...for like 40 you can eliminate the TV cable...I strongly reccomend doing so.
 
thanks a lot for the help, I don't plan on doing anything with the trans till I regear to 4.56 or higher. But one last question, After I regear should I stick with the 700 or go to a turbo 350 or 400?
 
350 is no stronger than a 700, provided that the Tv is set up properly and 700 has a lower first gear.
400 is stronger, but again not as low as a first gear
 
Ski Hi, what is the mod you are speaking of on the throttle valve cable? I havent seen that one yet. I asume you have to dissassemble the trans to install?

Thanks,
Tom
 
How did the fluid look when you changed it? Was it still red or blackened or smelled burnt? If the fluid is still clean the trans could still be in salvagable condition. Adjust the cable and try it then. It only takes a few minutes to learn it and dot it. I did mine once in like 15 minutes. Printed the instructions and wentt it. I would try it before I wrote the trans off as being bad. The 700r4 is a good trans but not as strong as som others. The lower first gear is nice as well. I swapped to a trubo 400 only becuase I had it and did not need the overdrive anymore since it is a trail truck only. Many guys run the 700 with more tire than 38's but the gearing is killing you. Don't bother regearing the stok ten bolts. Upgrade to a set of one tons with 4:56 or even 4:10's. I am looking for a set myself. They are not cheap bu the 10 bolts wont stand those tires for long if you like the go-peddle.
 
nctom said:
Ski Hi, what is the mod you are speaking of on the throttle valve cable? I havent seen that one yet. I asume you have to dissassemble the trans to install?
Thanks,
Tom
Click to expand...


Dang old thread....

I was not as clear as I should have been I suppose, but deleting the TV cable requires a manual valve body....but I and others as well prefer that anyway. Basically you get a clutchless manual, sort of.
 
You can have a manual valve body put in for about 600.00 BUT, you can buy two rebuilt 350 turbos for that much and I've seen 350t's run 44s all day long and never have any trouble. As far as the low fist gear, you don't need it. Once you gear the axles right, low range in the transfer case will be all you really need.
 
lilfoot said:
You can have a manual valve body put in for about 600.00 BUT, you can buy two rebuilt 350 turbos for that much and I've seen 350t's run 44s all day long and never have any trouble. As far as the low fist gear, you don't need it. Once you gear the axles right, low range in the transfer case will be all you really need.
Click to expand...


ok...again there is NO DIFFERENCE in strength between a 350 and a 700 they use the same dang components...

You do have to be smart enough to set the TV cable right.

But you are right, why would anyone buy a stak or an atlas, heck you can gear low enough for it.
What about when you are driving say on the street, gonna use low range for that too?

Remember trans gear gets multiplied by tc and then by r&ps its fairly hard to offset actually

BTW last 700 I rebuillt cost me less than 300 including beer......
 
im runing 36"s with a 4.3 to a 700r4 with 3.08s and had no problems but i am gitting 350 to drop in and some 1 tons under it with 4.56s
 
Back
Top