OK, another 700R4 thread.....with a twist

[bdumont]

Great website, it has been a great resource for me.

Ok, here is the deal:

1984 K10 6.2, 80K miles, never towed with, sees the trails about once a month, mostly 2 lane country road driving at 60MPH.

MODS: 6" lift, 35 BFG KM2's, Allied beadlocks, K&N dual 2.5's, driveshafts, not sure what gears, lockout hubs, fabtech spare mount, winch.

ABout 500 miles ago, I had the trans fluid flushed. It was not too bad, no debris. Truck hasnt seen trails in 2 months. Last week, I was driving at about 60MPH and it started to shake badly. I pulled over, checked fluid, and found nothing unusual. Now its doing this business where it runs just fine in first and 2nd, then skips 3rd, and hammers 4th hard with shaking. if I put it in 2nd or 1st, its fine. IN 3rd or 4th, it shakes hard at 1/2 or more throttle.

Its almost like when you are trying to run your lawnmower over a giant pile of grass or leaves, it bogs and almost stalls until you back off.

I replaced the TV cable and it made no changes, not matter how it was adjusted. Does this sound like a tranny pooping out, or a Torque Converter.

FWIW: I did stop drivng the truck once this happened.

Thank you in advance.

 

[Greg Ducato]

Sounds like a torque converter clutch shudder. Disconnect the voltage to the trans by popping the connector at the case and go for another drive. If it is still shuddering you may have some other issue but if it stops then you may have to have a look at that converter.

 

[BoondocK5]

It's either what Greg described, or something much more sinister...It may not be skipping 3rd gear, it may be in 3rd and 4th at the same time. Very bad things are going on in there.

 

[bdumont]

Sounds like a torque converter clutch shudder. Disconnect the voltage to the trans by popping the connector at the case and go for another drive. If it is still shuddering you may have some other issue but if it stops then you may have to have a look at that converter.

The connector on the drivers side of the tranny?

It's either what Greg described, or something much more sinister...It may not be skipping 3rd gear, it may be in 3rd and 4th at the same time. Very bad things are going on in there.

Yeah, it doesn't seem good at all, but I am trying to be optimistic here. The truck has had a relatively easy life and has been very well maintained. I don't have a problem tossing another tranny in there, if thats what is needed. I just want to be sure it's not something stupid first.

 

[BoondocK5]

Pull the connector, it should be a 4 wire square connector, is that correct?

 

[Greg Ducato]

The connector is on the drivers side

 

[diesel4me]

Easier way to keep the TC unlocked is to ride the barkes slightly,enough to activate the stop lite switch--it is wired into the TC to unlock the clutch when the brakes are applied..(assuming its adjusted right & working of course!).

 

[BoondocK5]

The connector is on the drivers side

Yep, unplug it, I'll wrap a plastic sandwich bag around it and zip tie it to keep the crap out.

 

[bdumont]

Pull the connector, it should be a 4 wire square connector, is that correct?

i am fairly certain that there is a 4 wire connector on the drivers side, I will confirm this for future reference to others.

The connector is on the drivers side

Thats how I remembered it.

Easier way to keep the TC unlocked is to ride the barkes slightly,enough to activate the stop lite switch--it is wired into the TC to unlock the clutch when the brakes are applied..(assuming its adjusted right & working of course!).

Great tip, I will try this too.

Yep, unplug it, I'll wrap a plastic sandwich bag around it and zip tie it to keep the crap out.

good call, the underside of this truck is caked with mess (had a nasty power steering leak for some time, it coated the entire undercarrage and mud stuck to it.)


I might try dropping the pan and doing a filter/fluid change. It just seems a bit fishy that it performed flawlessly and then had problems a few weeks after a fluid change. I had the fuid sucked out at Valvoline Instant Oil change, but they dont drop the pan and do the filter. The fluid that came out was dirty, but really not too bad.

 

[Blue85]

The only difference between 3rd and 4th gear is whether or not the band is applied. It's possible there is a bad seal in the servo so that it doesn't release like it's supposed to on a 2-3 shift. But this shaking sounds worse than the missing gear - like a broken part. It's possible that there is just debris sticking something up since you just had a fluid flush done. You should check the governor gear and the TV cable adjustment - just because those things are easy to do.

 

[bdumont]

OK, i dropped the pan. I found nothing unusual. There was the normal grey dust (shavings) on the magnet, filter had some very small dirt particles, but nothing I havent seen in a working tranny before.

Now, I did run into something that might be the root cause. The plug/wires leading into the tranny was in pretty sad shape. The plug was caked with mud, the plug itself was brittle and cracked apart. The safety clip part was broken off.

Now, my next question is: There are two leads leading into the tranny, but only one on the inside part of the tranny. However, I see three metal terminals on the tranny side of the plug.

When I went to put the new filter in, there is a orange rubber gromet up in the feed hole of the tranny. Is this fixed, or part of the old filter that needs yanked out?

 

[Greg Ducato]

Looks like someone may have converted the harness to a single wire style internally. In this method the trans will only lock up in 4th gear, there is no problem with that kind of set up and it is pretty common. Pull the old orange seal out, you will have a new one with your new filter.

 

[zombie1969]

Your trans sounds like its due for an upgrade to an 87 or newer unit.Skipping 3rd and slipping in 4th is bad.The early 700r4's were problem prone so do yourself a favor and ask for the later model when you get a rebuild.

 

[bdumont]

Your trans sounds like its due for an upgrade to an 87 or newer unit.Skipping 3rd and slipping in 4th is bad.The early 700r4's were problem prone so do yourself a favor and ask for the later model when you get a rebuild.

Let me clarify some. It still hits 3rd and 4th at part throttle. Under a load (hammer down), it "seems" as if it skips a gear or bogs somehow. I am not 100% sure that it is doing this. I parked the truck immediately when these symptoms popped up.

The closest thing I can think to describe it is when you bog down a mower in deep grass. (please refer back to age 7-12 years of age in the man-book). Poor description, but it's almost as if when I miss 2nd in my wifes car (subaru) and hit 6th.

 

[bdumont]

just a quick update for future refrence to others. It turns out that 3rd gear is reaching its final days. It was hitting 1st, 2nd, and tapping 3rd and jumping to 4th. If I put it in drive, it would still skip to 4th, since 3rd was not working correctly.