91 350, no kick down
- Thread starter cowboy450
- Start date
Molson02536
New member
Throttle Valve cable aka TV cable. Full pull of the TV cable at WOT is the first place to start with adjustments. The 700R4 trans is different from the t-350 which had a vacuum modulator on it for a signal of engine load, the 700R4 does not. If you don't adjust the TV cable properly you WILL ruin the trans.
Here is a good link for adjusting the TV cable to the 700R4 transmission with pictures. Good luck and keep us all posted.
http://purplesagetradingpost.com/sumner/techinfo/700R4p1.html
Molson02536
New member
Disconnect your TV and see if the problem persists in the same manor. The TV will only kick your tranmission down one gear to allow you more power for passing and should only be activated at WOT or very close to WOT.
If the problem does persist, I would suspect your governor is malfuctioning. It's a simple fix, springs and weights. May even just need some lube to free it up.
There are rebuild kits with different weights and springs availiable that allow you to change your shift points, if you want to also.
The governor is accessable from the out side. I think it's on the drivers side if I remember right. It's has a round access cover on it about 3-4" in diameter. The throttle valve in the 700R4 is not a kick down cable like a 350TH trans or similar. I learned a lot about this after doing a V8 swap in my earlier years. The transmission actually uses this valve to know the throttle position and uses this to adjust fluid pressure at different loads for different functions. Including kick down. It will not shift properly if it is installed incorrectly or not at all. The governor itself controls the shift points which would also cause the symptoms described above. My experience with the stock V6 700R4 with high miles behind a V8 is not good. I found them to slip terribly between 1st and 2nd and they burn up pretty quick. Especially if the TV cable is misadjusted. Even after the installation of a shift kit.
The later models of the 700R4 worked as described above, the earlier 700's were set up like the t350, and 400's used an electric switch for a kick down. There is a vacuum line that picks up a ported signal that locks up the T/C though a switch on the brake pedal, but I believe thats all it does.
Here is a link to your 700R4 to give you a better look on the parts that is used in your transmission.
http://www.compnine.com/index.php?u...delid=6556&capuid=1&majorgroup=04&grouptype=B
http://www.compnine.com/index.php?u...delid=6556&capuid=1&majorgroup=04&grouptype=B
http://www.compnine.com/index.php?u...delid=6556&capuid=1&majorgroup=04&grouptype=B
http://www.compnine.com/index.php?u...delid=6556&capuid=1&majorgroup=04&grouptype=B
http://www.compnine.com/index.php?u...delid=6556&capuid=1&majorgroup=04&grouptype=B
cowboy450
New member
The TV cable was disconnected when I got the truck, hooking it up made no difference. The shift points seem ok, just no kick down. Shift points may be a little low, do they normally vary depending on throttle setting?
Molson02536
New member
The shift points don't vary with the throttle setting, the Governor springs and weight regulate the shift points. To increase shiftpoints you use lighter weights/springs and the harder the springs will give it a lower shift point.
You heard this before, and took care of it before tearing the tranny apart, but it is critical that the TV cable is adjusted properly. The cable has to follow the throttle position just right, or you will have incorrect shift points and shift firmness. One click on the adjuster makes a noticable difference. Sounds like the tranny thinks you are driving at idle and shifting accordingly.
Here is a link to your TV system with picture to the cable hook up in the TB and the hook up on the Transmission Plunger, keep me posted as let me know if the plunger is in all the way at WOT and we can go from there.
Keep me posted.
Molson02536
New member
cowboy450
New member
Ok, I am going to have to put this on the back burner for a bit but I will be back. Right now my game plan is to tighten the cable a notch or two and pull out the govenor and clean and lube it. I'll keep you posted. Thanks for all the help.
cowboy450
New member
Ok, adjusted the TV cable so tight the throttle didn't quite open all the way. Checked the governor, nice and loose, plenty of lube. No change. I did have very firm shifts though. I would like to use this for towing but unless I downshift manually thats not possible. Any recommendations as to a shift kit and a source for governor weights and springs?
Last edited:
Molson02536
New member
Ok back to square one so we don't kill your transmission. It may have low TV Pressure/Line Rise and, if so, it's going to slowly burn itself to death. Not that it's proof positive of anything, but your 700R4 should never be without a low speed 2-1 kickdown.
If you don't have it, it's wrong for sure and it's going to slowly self destruct the 700R4. If you do have it, double check the TV cable adjustment. Here's what's may be happening, It's actually very simple.
There's TV pressure, TV stands for Throttle Valve and it's tied to your throttle body, The throttle angle. It performs downshifts. (Important for this unit.)
There's also an opposing force called Governor Pressure. It's tied to Road Speed in simple explanation.
TV Pressure get's higher as you put your foot into it.. In this unit, it also raises line pressure, which is the pressure that holds your clutches tight and keeps them from slipping.
With TV Pressure, the harder you romp it, the higher the pressure gets. With Governor pressure, the faster you travel, the higher the pressure gets.
Governor pressure throws a series of shift valves, in order, (Pascal's principles) and provides up-shifts. TV Pressure acts on the opposite side of those valves and shifts you down or holds off upshifting.
The problem in the 4L60/700R4 is that TV Pressure is directly tied to line pressure. The only way the transmission can estimate engine load is via TV pressure, and the TV cable. Thus, if you get late or no downshifts.. You may very well have low line pressure as a result and your clutches slip, destroying your transmission over time.
TV Cable adjustment is critical. It's the number one killer of "rebuilt" 4L60/700R4 type transmissions.
Here is a link to the line pressure reading and how for you to test the line pressure. http://www.tciauto.com/Products/TechInfo/line_pressure.asp#TH200700
http://www.tvmadeez.com/press_gauge/index.php
cowboy450
New member
I'll see what I can do about digging up a guage. I have one that goes to 160 so maybe I could check the lower readings. Thinking back I may have had a downshift when I first test drove, before the trans warmed up. That would sound like low pressure to me, as the fluid warmed and thinned out the pressure dropped.
cowboy450
New member
Ok, according to the sites you sent me to I have Short Spring Syndrome. As I'm sure the TV has been adjusted both directions without much change I am going to change the TV spring. Any idea where to look for this?
Molson02536
New member
Here you go everything you need to know is in the link i gave you on the previous link. The repair is about a $5.00 fix for the new spring, but your going to have to drop the transmission pan to get to the TV Plunger to remove the spring. Keep me posted and keep up the great work.
http://www.tvmadeez.com/spring_install/700r4.php
#4XX. 700R4 throttle valve elevated pressure spring. The original TV valve spring is a bit weak resulting in low line pressures and insufficient throttle pressure. If left uncorrected this can result in premature 3-4 clutch failure. Cost $5.00 http://www.transmissioncenter.net/77968-01k.jpeg
http://www.transmissioncenter.net/performance_automotive.htm
Molson02536
New member
Automatic Transmission, THM700-R4 Initial Fill..........4.7 liters
Automatic Transmission, Total Fill 4 speed THM700-R4..........10.9 liters
Keep me posted, be glad to help you get your transmission working 110% again soon. You may want to add and external transmission filter along your transmission line to the radiator. B&M has them for around $35.00 and takes less then 30 min to install, great investment to keep your transmission fluid always clean.
cowboy450
New member
Ok, finally got the spring in. It was about 1/8 longer than my old one. I'm still not sure but it does seem to do better. The pan has the usual grey gunk but not too much, very little metal on the magnet. I'm thinking I may just need to get used to the truck at this point. I think it may just shift differently than my Jeep or Dodge. I had to replace a head gasket so it has taken me a while to get everything back together. I'm in SC and the heat has really slowed my projects down. Thanks for all the help, I'll post an update after I drive it a little.
Molson02536
New member
Good job, but keep a close eye on your set up to make sure you don't burn up your transmission. The metal found on the magnets are from bushings and the gray material is the clutch and is normal to find when servicing the transmission.
Keep us posted and more transmission shop will test drive your Suburban free of charge to give you some advice on what can be done since there looking for your business.
cowboy450
New member
Update:
Sorry it took so long but I just actually got it finished today. Ok, nothing to this point had helped. I put in a quart of Lucas tranny stuff, big improvement especially while cold. One more quart even more improvement, actually fairly drivable until about 15-20 miles when it went back to bad again, shifts too close, sloppy 2-3 shift. I drive 25 miles to work so I could live with this for a while. Installed a Transgo Jr. kit. Improved everything especially the sloppy shift, still had problems sometimes after 20 miles but not alway. Finally got it into a shop today. I haven't talked to the mechanic yet but apparently the valves bores in the valve body were worn so as the fluid heated up it lost pressure. He had said he was putting in a full Transgo shift kit but I don't know exactly what he did until I talk to him on Friday. I had talked to a few other shops and got the answer I was afraid of. Without even seeing it the said it needed rebuilt. This was an older guy who has been in business for over 30 years, has a great and well deserved reputation. He charged me $160 for what he did. Bottom line, the trans shifts great!
Sorry it took so long but I just actually got it finished today. Ok, nothing to this point had helped. I put in a quart of Lucas tranny stuff, big improvement especially while cold. One more quart even more improvement, actually fairly drivable until about 15-20 miles when it went back to bad again, shifts too close, sloppy 2-3 shift. I drive 25 miles to work so I could live with this for a while. Installed a Transgo Jr. kit. Improved everything especially the sloppy shift, still had problems sometimes after 20 miles but not alway. Finally got it into a shop today. I haven't talked to the mechanic yet but apparently the valves bores in the valve body were worn so as the fluid heated up it lost pressure. He had said he was putting in a full Transgo shift kit but I don't know exactly what he did until I talk to him on Friday. I had talked to a few other shops and got the answer I was afraid of. Without even seeing it the said it needed rebuilt. This was an older guy who has been in business for over 30 years, has a great and well deserved reputation. He charged me $160 for what he did. Bottom line, the trans shifts great!