700R4 Lock Up Converter Talk and Diagnose

[Jims86]

Right. Now I got a lot of slop in the shifter linakge, so that may be an influence?

Hmmmm....I dont think so. ya know, TCC is supposed to lock up in 3rd too, and ifnit has any influence on it, and depnding on how much slop there is, when you are in OD, the switch could possibly be hanging in N. But if your reverse lights operate when they are supposed to, the switch is good.

 

[HotRodPC]

Yeah, I"m thinking you've gone as fasr as you can go on this without getting dirty. It could be a bad TCC solenoid and possibly even a bad TCC clutch. You don't drive much though do you? Might not be worth all the work Dawg.

 

[89Suburban]

Yeah, I"m thinking you've gone as fasr as you can go on this without getting dirty. It could be a bad TCC solenoid and possibly even a bad TCC clutch. You don't drive much though do you? Might not be worth all the work Dawg.

I want to get around to changing the fluid and filter so I will look into the solenoid. Sound like a plan Lug Nut?



Is there a way I can test just the solenoid? I can go under there truck and find the connector and test if there is power to it right? Then run a ground jumper to the cab to test? Jim?

 

[Jims86]

I want to get around to changing the fluid and filter so I will look into the solenoid. Sound like a plan Lug Nut?



Is there a way I can test just the solenoid? I can go under there truck and find the connector and test if there is power to it right? Then run a ground jumper to the cab to test? Jim?

They have it at Advance over on Ridge Pike for $33. The only way to test it is to pull it out and blow through it while applying 12 volts to it.
I forget...did you inspect the four wire plug on the drivers side of the trans?

 

[89Suburban]

They have it at Advance over on Ridge Pike for $33. The only way to test it is to pull it out and blow through it while applying 12 volts to it.
I forget...did you inspect the four wire plug on the drivers side of the trans?

No. Wher is it, near the shift linkage? I got to climb under there anyway to check the linkage out. Loose as ****. Pissing me off. There should be a plastic cup on the frame side of the shift rod right? I got to look at some diagrams in the library....

 

[Jims86]

There's not on mine the last time I looked, just a spring. There are nylon grommets that wear out though.
The Lockup plug is up and behind the shift linkage....the only wires going to the trans.

 

[bucket]

No. Wher is it, near the shift linkage? I got to climb under there anyway to check the linkage out. Loose as ****. Pissing me off. There should be a plastic cup on the frame side of the shift rod right? I got to look at some diagrams in the library....

Well shoot, I still have all the linkage from my Burb, I could have stuffed it in the box too.

You must be registered for see images attach

 

[89Suburban]

Well shoot, I still have all the linkage from my Burb, I could have stuffed it in the box too.

You must be registered for see images attach

I am sure there will be another exchange at some point in the future.

I am just curious what the actual wear parts are that I can replace. Like bushings or stamped springs, etc. I will have to look on LMC when I find the time just to get an idea.

 

[Jake292]

Just my 2 cents... The reason the you should pull it into 3rd when towing is to save the sprays inside the tranny. When in 3rd the clutches are used instead. The sprang is what allows you to coast.

As far as the lock up converter goes, I have no clue if it will lock up in 3rd or not.

 

[bucket]

My '88 locks up in third.

 

[89Suburban]

Ok, I just climbed under there and looked, the plug is connected to the trans. Looks like 3 wires, tan, purple and green maybe? Can I test it there somehow?

 

[Jims86]

You can check the Purple wire for power with th key on.
Was just looking at the diagram, and there looks to be a diode in the TCC solenoid...if that diode is bad, that would splain the popped gauge idle fuse when you grounded f.
Thebgreen one(really lt blue) is the signal wire frome the high gear switch to the ECM, and the tan wire is the lockup wire from the ecm, and pin f.

 

[89Suburban]

Was just looking at the diagram, and there looks to be a diode in the TCC solenoid...if that diode is bad, that would explain the popped gauge idle fuse when you grounded f.

Very interesting.

 

[HotRodPC]

Just my 2 cents... The reason the you should pull it into 3rd when towing is to save the sprags inside the tranny. When in 3rd the clutches are used instead. The sprang is what allows you to coast.

As far as the lock up converter goes, I have no clue if it will lock up in 3rd or not.

I know what you're saying here. I really wish it were sprags, but actually it's roller clutches in the books IIRC, which are much weaker than sprags. It's a nit picky difference in lingo I know, but if the guys who aren't transmissions guys go looking for sprags in the book, they'll likely never find it, so being politically correct, roller clutches.

This is also why when diagnosing transmissions, you also use manual selected gears. Many are not aware that using manual selected gears uses a different fluid circuit and actaully uses a different method to create the gear. Same goes true when diagnosing a band. You might have 2nd this way, but not have it this way. Whichever way you have it and don't have it can tell you if it's a band or not. Bands actually aren't used near as much as most think. I'd have to look at a flow chart since i don't momorize that stuff since different trans models are different, and the minute you think you got it, it's no wait, that's the Th400, not the Th350 or vice versa.

A good example of this is when you're in D and the trans is in 2nd gear. When in D and trans is in 2nd gear, drop it into manual 2nd gear. It'll feel a bit like it downshifted, but NO it didn't. It changed the routing of how it's getting 2nd gear. At any rate, good point to bring up Jake.

 

[HotRodPC]

Very interesting.

Yeah, get this fixed already wouldja Dawg??? Curiosity is starting to kill me on this deal. I'm about ready to pull the Th350 out of the K1500 and put this 87 700r4 that's supposed to work into the K1500 just to play with Lock Up TC. Of course it's going to be different cuz mine will work off activation by Vac switch on the firewall, yours will work off signal from the ECM. Of course that doesn't really matter. The signal goes to the same place, just gets its from a different source.

I don't recall the pinout on the connector, but I'd almost like to see your run a hot wire from the battery thru a toggle or push button swtich to the connector so that you're making your own signal and see if it works. What this will do is, confirm if the problem is in the transmission in front of the connector, or if the problem is behind the connector which would be in the wiring or the signal source. Know whudda mean???

So if you hook up a hot wire and it works. The you know the problem is NOT in the trans and the problem is BEHIND the connector.
If it still dont' work and you've confirmed you wiring and signal from the ALDL, then most likely the problem is in FRONT of the connector and inside the transmission, most likely to be the TCC solenoid.