What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

700r4 lost all gears while driving

D

dudewiththeblue82

Registered Member
Joined
Mar 23, 2024
Posts
12
Reaction score
4
Location
South Carolina
Hey all. I just recently had some trouble with my 700r4.
I lost all gears while driving down the highway. I recently rebuilt the engine (6.2 turbo) and transmission and replaced the old torque converter with a remanufactured one. So far I've put about 100 miles on the build and everything was going well, engine runs strong and the transmission was shifting perfectly. I put the tcc on a manual switch and would lock it in once I got up to speed. Now the other day I went to engage the lockup at about 55mph, but the locukup started engaging and disengaging very fast, so I quickly turned it off and kept on driving to town without the tcc engaged (about another 5 miles), and everything still continued to shift normally after that. On the way home though, I tried the lockup again and it caused the transmission to downshift from 4th to 3rd. I turned it off and it shifted back to 4th, and then tried again and it downshifted. After one more time of that I completely lost overdrive but it was still pulling good in 3rd without any slippage, but then about a half a mile down the road I completely lost all gears, like it just jumped into neutral. I borrowed a trailer to tow it home, and after sitting a while it went into gear fine and drove onto the trailer (with enough pull to even spin the tires with posi traction getting onto the trailer). Shortly after running though it lost gears again. I took the pan off and had pieces of metal shavings and torrington bearings. I'm thinking the insides of the torque converter went out? Everything was literally perfectly fine until the moment I engaged the tcc on the way home. I'd post pictures of the pan but I'm not sure how to do that on here, or if I even can.

Sorry for the long essay. Just trying not to leave out anything important
 
Are you saying that the transmission was rebuilt along with the engine?
With my limited knowledge, it would be difficult to say what failed without a complete teardown. But that's going to be necessary now anyway due to all of the metal getting sent wherever it can go inside the trans.
 
It seems clear that all roads lead to pulling the transmission out and tearing it apart. Any chance you have a warranty?

Why the manual switch on the TCC? Is this a 1982 and does it still have the factory lockup controls? It's possible your switch is just in series with that. Why would it downshift when the clutch tries to engage? I can only guess that the load on the engine was increased due to something being fragged. It is very possible that something gave up inside the converter and you went to full neutral when the shrapnel broke the pump.
 
Blue85 said:
It seems clear that all roads lead to pulling the transmission out and tearing it apart. Any chance you have a warranty?

Why the manual switch on the TCC? Is this a 1982 and does it still have the factory lockup controls? It's possible your switch is just in series with that. Why would it downshift when the clutch tries to engage? I can only guess that the load on the engine was increased due to something being fragged. It is very possible that something gave up inside the converter and you went to full neutral when the shrapnel broke the pump.
Click to expand...
No factory controls are left for the lockup. That was all boogered up when I got the truck so I just put my own circuit in. I did run it through so when coasting the converter will unlock as not to stall ouy. It's a 1982 truck actually but it has a 1989 transmission. The converter does have a warranty. I just don't know if the converter tearing up in such a manner is normal for these transmissions or not. It definitely is pretty clear at this point I'll have to tear it down and inspect, but knowing if the problem is the torque converter would help pinpoint. And it would at least make me feel better that is wasn't anything I did with the rebuild lol
 
Even on a diesel the 700 should have a tv cable hooked up to the throttle lever on the injection pump. Incorrect adjustment to the cable can cause quick failure to the entire trans. It it wasn’t tight enough it probably kept the line pressure lower than it should have been and started wiping stuff out.

It’s crucial to get that adjusted right.
 
I haven't had a convertor failure on one so far, but that doesn't mean squat, honestly. Things can happen.
I wouldn't say that is the #1 failure, myself.
 
ZooMad75 said:
Even on a diesel the 700 should have a tv cable hooked up to the throttle lever on the injection pump. Incorrect adjustment to the cable can cause quick failure to the entire trans. It it wasn’t tight enough it probably kept the line pressure lower than it should have been and started wiping stuff out.

It’s crucial to get that adjusted right.
Click to expand...
TV cable is adjusted correctly and I do have the original brackets so nothing should be wrong there. That's kind of why I'm leaning towards the torque converter rather than clutch packs. It was pulling fine with no slippage and then just lost everything right away. No foward or reverse
 
dudewiththeblue82 said:
TV cable is adjusted correctly and I do have the original brackets so nothing should be wrong there. That's kind of why I'm leaning towards the torque converter rather than clutch packs. It was pulling fine with no slippage and then just lost everything right away. No foward or reverse
Click to expand...
Sounds logical.

I will share the experience that my son had with a 4L60E. He did an immense amount of research before building it. He was told not to buy the $300 billet pump rotor because it wasn't necessary for his intentions. Well, we goofed up and didn't verify pump pressure soon after initial test drive ans such. A month later, not more than 1000 miles, it shattered the brand new, stock replacement pump rotor.
It quit pulling immediately.

So the fact that yours didn't quit immediately, tells that the pump was working.
 
Well Torrington bearings didn't barf out of the converter, wash through the trans and land in the pan. That could be part of the cause, and could be collateral damage.
 
dudewiththeblue82 said:
It's a 1982 truck actually but it has a 1989 transmission.
Click to expand...
1989 didn't have the lockup control valve in the valve body, but a form of automatic locking is still possible. One way is a pressure switch for 3rd/4th gear, combined with a vacuum switch to the manifold. The problem with full manual lockup is that you can abuse the TCC and make it fail. Even if you you are wired in series with the brake switch (which of course you should be), you can leave it engaged as you come to a stop and as soon as your foot comes off the brake the engine stalls. You also shouldn't have it engaged while shifting or really at any high load and the vacuum switch really helps with that.

However, you can often blow out the TCC with no other ill effects on the transmission - there just isn't lockup anymore.
 
TCC won't engage until 2nd gear, so no worries about stalling, just lugging when it shifts to 2nd and immediately locks.
 
In those years, all lockup control was done by the ECM and it can be engaged at any time using the ALDL port.
 
6872xtc said:
TCC won't engage until 2nd gear, so no worries about stalling, just lugging when it shifts to 2nd and immediately locks.
Click to expand...
Yes that it why I had it on a manual switch. I would only engage it when up to speed, and made sure to always disengage it when coming to a stop
 
dudewiththeblue82 said:
Yes that it why I had it on a manual switch. I would only engage it when up to speed, and made sure to always disengage it when coming to a stop
Click to expand...
I have two trucks set up with a switch. One is an '88, the other is a '90 case. One behind a big block. It has 50K on it in an application that it was never intended for! :D
I have used the TCC lock in 2nd gear, low range to cool the transmission down some after screwing around running a trail. I will even use the lock-up at low rpm, low speed, light throttle across town. Most will not recommend half of what I do, but I know how the guy built mine, so they both have handled it well.

@Blue85 there is no oil available for TCC in 1st gear, in a OEM style valve body.
 
You must be right, if Greg agrees with you. I've never taken that kind apart. It's just something I remember reading here - to not leave the ALDL jumper in place for risk of both stalling and damage.

Greg Ducato said:
If you are pulling a long grade it is advantageous to have the converter unlocked so it can provide torque multiplication as it was designed to do. The 700 can be locked up in any forward gear except first, oil for the TCC comes off the 2nd gear shift valve. It is unwise to shift with the converter locked, the 700 is not a strong trans and the shock can break the input shaft or the input clutch drum. There is a damper on the converter clutch that helps but it is still not advisable. Factory lockup strategy was unlock under heavier throttle or off throttle, that gave the best performance results and longevity to trans components.
Click to expand...
 
Blue85 said:
You must be right, if Greg agrees with you. I've never taken that kind apart. It's just something I remember reading here - to not leave the ALDL jumper in place for risk of both stalling and damage.
Click to expand...
I can see that scenario keeping it locked, bypassing the brake switch, which could lead to stumbling, possible stalling when approaching a complete stop. It doesn't unlock until downshifting into 1st gear.

@dudewiththeblue82 I will be interested to see what you find upon teardown.
 
Well I've torn the whole thing down, and it looks like I just didn't have enough end play in the transmission. All the thrust washers have taken a beating, and it ultimately failed at the rear planetary set because it burned up. The thrust bearing inside that planetary set was ground to almost nothing. I bought another rear planet set, and the reaction shaft for the front planetary set because it got hot too. All the other hard parts seem fine, except for the reaction sun shell because the plastic thrust washer behind it came apart, so it was just metal on metal at that point. I bought the sonnax smart shell for a replacement. I'm guessing the reason it was dropping out of gear with the tcc is because the pressure coming out of the front of the input shaft to engage the lockup was forcing the input shaft backwards, and since there was now so much end play from the thrust washers and bearings wearing out that it caused the sealing rings on the input shaft not to seal the pressure going to the clutch packs, ultimately resulting in having no drive gears.
 
You must log in or register to reply here.

Latest Posts

Top Bottom