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Old 04-16-2018, 02:06 PM   #1
mister.freeze
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Calling all 700R4 Experts!

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

Iíve 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 doesnít 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 Iíve 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.
Hereís 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.
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Old 04-16-2018, 07:27 PM   #2
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Re: Calling all 700R4 Experts!

What carb/intake are you running and what brackets do you have for the tv cable?
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Old 04-16-2018, 09:36 PM   #3
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Re: Calling all 700R4 Experts!

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
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Old 04-16-2018, 10:00 PM   #4
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Re: Calling all 700R4 Experts!

LOoks like this
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Old 04-17-2018, 10:47 AM   #5
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Re: Calling all 700R4 Experts!

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.
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Old 04-17-2018, 11:21 AM   #6
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Re: Calling all 700R4 Experts!

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.
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Old 04-17-2018, 01:15 PM   #7
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Re: Calling all 700R4 Experts!

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

http://www.bowtieoverdrives.com/cata...php?ITEMID=321
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Old 04-17-2018, 03:24 PM   #8
Jesse B.
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Re: Calling all 700R4 Experts!

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

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Old 04-17-2018, 07:33 PM   #9
60case
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Re: Calling all 700R4 Experts!

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.
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Old Yesterday, 12:44 AM   #10
mister.freeze
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Re: Calling all 700R4 Experts!

Is that piston easy to check?
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Old Yesterday, 09:28 AM   #11
60case
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Re: Calling all 700R4 Experts!

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.
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