700R4 Gear “Hunting”

[Burbinator]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

 

[Ricko1966]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

Find out quick, or you will need another transmission rebuild.You can check your flyid,if it's OK. You need get a transmission pressure gauge

 

[gmbellew]

Are you sure it is the 3/4 shift bouncing or is it the TCC hunting? Could be an issue with the TCC lockup solenoid?

Does the issue go away if you keep it in D?

 

[Burbinator]

Are you sure it is the 3/4 shift bouncing or is it the TCC hunting? Could be an issue with the TCC lockup solenoid?

Does the issue go away if you keep it in D?

When in what I call D3 (Not overdrive, 1-3) it doesn’t seem to. Where is that solenoid?

 

[gmbellew]

When in what I call D3 (Not overdrive, 1-3) it doesn’t seem to. Where is that solenoid?

solenoid is accessible with a pan drop. but if it doesn't hunt in D, it probably isnt the TCC lockup unless yours has been modified to not lockup in 3rd. then it could still be the solenoid if it has been changed to not lock in 3rd.

 

[bartarfonz]

A miss-adjusted Brake Switch or associated wiring can also cause Torque converter lock-up to cycle off and on as well. This could happen in 2nd, 3rd, or 4th Gear. Usually your cruise will drop out too if you have cruise control. The solenoid is in the pump and is managed by the ECM. Fluid to the convertor apply valve is managed by valve 227 in the pump and vented through the solenoid when TCC is off. When TCC is on, the Solenoid is commanded on and the fluid exhaust is blocked so a leaking solenoid can be the cause (Could be an intermittent open electrical circuit or a leaking hydraulic circuit).

 

[Burbinator]

I seem to be having issues with bad grounds. Windows, not starting, etc. Would that effect hunting gears while driving?

 

[bartarfonz]

It Could be poor grounding condition that affects the ECM and its ability to keep circuits properly managed. Also note that your comment about the misadjusted TV cable could cause it. There is also the possibility that the Cooling fan is turning on and off because of a hot engine and it sounds like the transmission is changing speeds, but it is really the cooling fan clutch turning on and off.

 

[NickTransmissions]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

Have you figured out the problem as of yet?

If no, what troubleshooting and/or fixes have you tried?

How many miles on the transmission?

Bad grounds will impact your TCC control as it's electro-mechanical and commanded by the ECM which is also tied to the vehicle's electrical system. But hunting/shuttle shifting between third and fourth gear would not as the 700r4 is purely mechanical outside of the converter clutch.

Conduct a driving pressure test w/the gauge threaded in to the line pressure port on the driver's side of the transmission, just behind the bell housing (7/16 plug). See what line pressures do when shifting between third and fourth gear - particularly what's happening when it starts shuttle-shifting...Let us know and we can go from there.

Typically, falling out of fourth gear (which is technically what is happening, if you're not romping the gas or hitting the brakes) is failing 3-4 clutch pack.

 

[Burbinator]

Sorry for the late reply been super busy. Hoping this might be the problem. All the main power and ground wires look like this

 

[Burbinator]

So since my last post I’ve lost my mind. I did the main grounds and hot wires, and did the big 4 upgrade. Also did new plugs and plug wires.

Started it up after finishing about 2 days ago and it idled amazing (used to idle high). Took it on the freeway, no hunting. Took it up big hills, no issues.

Today i drove it and the idle is back up, hunting is back, voltage gauge inside says 9v but a meter check on the Alt and Batt says 14.2v-14.3v, the idle when sitting in park is raising and lowering by itself, etc. Oh and the oil pressure gauge will read fine, then spike, then do whatever it wants.

Questions: What in the ever loving HELL is going on?! Is the engine spark control module by the intake manifold getting too hot? Are there more stupid grounds im missing? HEEELLLPPPPP

 

[Broken85]

Unplug the wire harness on the passenger side of the trans. This will bypass the TCC completely. If you still have problems, I’d say it is the 3/4 clutch pack or you have pressure problems in the trans.

 

[Burbinator]

Well I had taken it to a shop and he said it’s the valve. I asked if it could be an electrical problem and he said absolutely and than bad grounds can kill a transmission. I have nothing but electrical issues with this rig and it did stop hunting the other day after I did a bunch of work. I think something somewhere is loose or is a partially broken wire and it’s making it intermittent.

I agree normally it’d be a clutch pack or valve but it wouldn’t magically fix itself and then happen again. I had a 3-4 go in my 86 burn and it cost me $2k to fix.

So are there any grounds linked to that valve harness and where do they ground out? Or other wires that may ruin it? If needed I’ll make a separate post

 

[gmbellew]

There is a TCC wire that is also on the gage/idle fuse. Runs along the driver side of the trans. I had a rub through that blew the fuse. Might be it is rubbed through enough to cause issues but not blow the fuse yet?

Edited to correct fuse circuit

 

[Ricko1966]

His problem is not isolated to the transmission. It's electrical also affecting dash gauges.. Run a volt drop test from battery negative post center,or center of side post bolt to engine block. Put a meter in volt scale 1 lead in center of battery post other lead on a goid ground,have someone crank the engine while you look at the meter. If it shows less than .5 volt your good,more than .5 volts you still have a ground problem. Not clean enough connections etc. You did run the negative battery cable directly to engine block didn't you?