Calling all 700R4 Experts!

[mister.freeze]

1972 K5 4x4, 350 SBC (300hp), 700R4, NP205. 33x12.50xR15 tires. Stock differential gearing. Torque converter lockup NOT hooked up. OK, so here’s the problem:

I’ve had this setup for years. It was never very good at downshifting, and I suspect bad geometry of the cable linkage on the carburetor. TV cable properly set, but, as I said, the bad geometry doesn’t pull the cable hard/far enough for good downshifting based on throttle position. The issue now is 4th gear (OD).

Normal driving is generally under 50 mph. My daily commute is 12 miles one way on city streets. I rarely get fast enough long enough for 4th gear to engage. This transmission was built about 7 years ago, then stored for 5, and I’ve been driving it daily for almost 2 now. Sild 1-2 shift and much softer 2-3 shifts. Rare shifts up to 4, but it was there any time I was on the highway.

I changed the fluid and filter 4 months ago (my first mistake, right?), and had normal operation for 1500 miles. The fluid was darker than new, but not burnt or smelling bad. Then I noticed frequent 2nd gear starts from lights and stop signs, so I added some Lucas Transmission oil (1 bottle). Shifting improved quite a bit, but was much delayed when cold. This is when I noticed no more upshifting to 4 at any time, even on the highway.
Here’s where it gets weird. Under normal power, a manual shift from 4 to 3 yields no change. However, when coasting, a manual 4-3 shift results in an actual downshift. ??? I understand that without the torque converter lockup connected, a shift into 4 can be almost undetectable. Would connecting it fix this problem with 4?

I also suspect that the TV cable might not be returning as smoothly as possible. Might a new cable be all I need if this is the case?
Thanks in advance for any help.

[SeventyOne]

What carb/intake are you running and what brackets do you have for the tv cable?

[mister.freeze]

800 cfm Holley with vacuum secondaries on an Edelbrock Proformer using whatever bracketry came on it. Used to have a 650 and the performance was the same

[mister.freeze]

LOoks like this

[Jesse B.]

I installed a 700R4 in my 69. You have the wrong TV setup and as a result, you may be burning up your tranny. The 700R4 cable that you hooked up to your carb does not serve the same purpose as the cable on a TH350 or 400 and so it cannot be installed in the same manner. The position and geometry is all wrong. Generally speaking, the range of motion on the cable must match the range of motion on your carb. Your current set up does not do that. If it does not, your tranny is not getting proper feedback from the carb. There is no shortage of websites that discuss this issue. Many folks have burned up 700R4s in the same way. I suggest you stop driving your truck immediately and install the correct 700R4 TV linkage on your carb. I used the brackets/linkage from a company with the initials BTO. (I don't know if I can say the actual name.) It bolts directly onto your existing carb and restores correct geometry so that the carb conveys accurate information to the tranny.

I also suggest you hook up the lock up. Driving around in 4th with no lock up will generate extreme amounts of heat on the freeway and can also burn up your tranny.

[mister.freeze]

Like I said, I've had this setup for years. I get the heat thing without the lockup, but 98% of my driving doesn't need it. I rarely make it up to 4.

I guessed the geometry was probably wrong long ago when it never downshifted correctly. I guess I need to know the length of the linkage from the pivot of the butterflies to the attaching point of the TV cable.

Perhaps 4 is indeed just gone, giving me a 3-speed transmission. Probably shouldn't have changed the fluid. I'll try the right bracket and a new cable; I was just wanting more input from folks that know more than me.

[SeventyOne]

Not sure if you have a spread or square bore holley but look here:

http://www.bowtieoverdrives.com/cata...php?ITEMID=321

[Jesse B.]

Here is a picture of the BTO system brackets on my Edelbrock carb. Note that the tranny cable is tight with no slop.

[60case]

When you shift from 4 to 3 manually it applies the over run clutch so you have engine braking. Both 2nd and 4th use the same band just uses different pistons on the apply shaft. Get the TV cable hooked up right and get TCC working.

[mister.freeze]

Is that piston easy to check?

[60case]

The piston is under the servo cover on the passenger side of trans. Remove snap ring pull out cover. Then you have to get seal out of cover to remove cover. The 4th piston is the outer one. I have never seen the 4th piston or seal bad but you never know.

[mister.freeze]

How do I check that piston?
Methinks the TV cable may have slipped some, but I still cannot get it up to 4. New TV cable going in tomorrow with a geometry corrector. That should help function and even downshifting, but I don’t think it will give me back 4th gear.

[60case]

Make sure the piston is not cracked. Check the lands on each side of the seal and make sure the seal is good. The piston seals inside the cover. The apply oil comes out through the center of the apply pin.

[YoungPup1977]

adjust your TV cable by using a pressure gauge, this way you know its adjusted correctly, by looking at your linkage I can not tell if there is slack in the cable or not but it appears to be at the end of the cable....start with adjusting the TV cable first....
Other possible issues could be a sticky TV valve in the valve body, 700R4's common issue, in the transgo shift kit a new self cleaning TV valve comes in the kit, it works....

as far as second gear starts, pull the gov out of the side of the trans and see if its sticking...hold the gov up by the gear with one hand as with the other hand squeeze the two weights inward, you should see the gov valve move up and down...."gov gear pointing to the ceiling"
Check the gear on the gov. Loose ? Replace the gear or the gov as required.
Hope this helps and makes sense....

Good Luck...

[mister.freeze]

With any luck, I’ll be changing the TV cable tomorrow. I’ll have a look at that governor and valve. What kit are you referring to ?

[mister.freeze]

Second gear works well. That means the band is good, right?

[Bigdav160]

I am not sure what transmission you have because that is NOT a 700R4 cable. It's a TH350 cable and would burn up a 700R4 in short order.



If that is not your bracket can you post a pic of your setup? It sounds to me that the TV valve might be sticking in the valve body. And hooking up the lockup clutch would be helpful especially with the big tires (and what gear 3.08?)

[mister.freeze]

That ibracket is the same as mine, but NOT a pic of what I have.
3.73 gears. Daily use is not a problem not having 4 or the lockup. The rare occasion I’m on the highway, I know I need both. Historically, the transmission never downshifted well, and would just try to lug in 4, especially with the lockup.
I’m thinking (and hoping) the cable is hanging up in the sleeve, giving the same effect as a sticking TV valve.

[mister.freeze]

Thus is what I have

[Bigdav160]

That is the TH350 kickdown lever. You should consider installing the correct adapter linkage.

http://youtu.be/HWurb3N3ZCU?t=67

[mister.freeze]

That’s all well and good, but I’v Had this setup for years, as described above. I agree the right geometry will be better, but the problem at hand is no 4th gear. This is a fairly recent problem and not related to the bracketry. Also, why is the right bracket so expensive? With a few measurements, how hard would it be to fab?

[Rickysnickers]

I don't know, but looking at your picture, it appears as though there's not a lot tension on the TV cable. That could be part of the reason for no 4th gear.

[mister.freeze]

That kink is deceiving. However, as stated before, it could be hanging up in the sleeve. I have a new cable, just have to put it in.

[YoungPup1977]

How are the 1-2, 2-3 shifts ? and the 3-4 is not happening as you stated....at what speed are they happening ? early/late ?

In 4th the 3/4 clutch is applied and the 2/4 band is being held, but you have a good 2nd and 3rd correct ?

Have you changed the TV cable adjustment at all and it made a difference in the shifts ?

[mister.freeze]

Shifting from 1-2-3 is about what it has always been. Trouble started about 1500 miles after changing the fluid. My commute is 11.2 miles one way, and I never get over 45mph. 1-2 is firm, tiny flare 2-3. It’s been like that for years. 3-4 was almost always after settling in to my final speed and letting off the gas ever so slightly. Tiny adjustments to the cable will advance or retard shifting appropriately. Because I never get up to much speed, I kinda felt I was rarely fast enough fir 4th. Highway driving has proven otherwise.