700R4 Can Survive Without Locking Torque Convertor

[ZZ]

I just made a 650 mile round trip to El Dorado Arkansas this week in 100+ heat with my 700R4 and the locking t/c not working. I averaged around 60 mph and the tranny temp guage never went over 110. I do have a medium duty cooler mounted with an external tranny filter kit installed.

As many of you have read my posts in about the last year know that my locking convertor will not engage after 10 miles of highway driving. It works fine around town but not on the road.

This is not a thread asking for help. I just wanted to say that you can "get by" without burning up a 700R4 if the locking tc doesn't work if you baby it around.

[DmaxMaverick]

That's great, but....

Are you sure that temp isn't

[ZZ]

Thanks for the response. The temp runs here in town around 160, but drops considerably on the road. I never run the truck under load. I use it more like a car.

I wonder sometimes if the tc isn't somehow manually locking on its own at highway speeds since I don't feel a change from toggling the manual switch that I have on it. Something has to be up since it has lasted over a year like this and the fluid stays a pretty red.

I also recently put a deep chrome pan on it and there was very little gunk in the bottom of the old pan. Probably the break in wear from the last rebuild. I put the remote filter on it a few days before I changed pans.

[ZZ]

[quote]Originally posted by DmaxMaverick:
[b] That's great, but....

Are you sure that temp isn't

[twaddle]

Hi ZZ,
Generally the temperature pick up sender should be located so that it picks up the oil temp at the torque convertor outlet, as close to the convertor as possible.
This is always the hottest point of the transmission.

Regards

Jim Twaddle
Biggar, Scotland

[BC Clark]

After having burned up a 700R4 that did not lock up in OD my personal experience is no it will not. This happened in a gas (350) 'burb climbing through Kingman AZ in the summer. After having it rebuilt, I added a large external cooler (B&M) and the Perma-Cool external spin-on oil filter (Summit Racing). The oil filter has a temp sender and basically reads exit temp as I have it first thing before the coolers. With everything locked up and in OD the temp will run well below 180. As soon as the TC unlocks it will quickly soar to 220 or so. Pulling it into 3rd it will drop back down. I can see why you don't tow in OD. In OD the pump doesn't turn fast enough to flow enough oil to dump the TC heat. I note that some after-market rebuilders say they open the oil ports up for the RV transmissions for increased flow. I guess I have to question those numbers too, as a minimum your transmission is starting with fluid that is at least as hot as the radiator. It does not seem unreasonable to me that the transmission is going to run around the same temp as the engine after everything stabilizes. I did locate my external cooler after the radiator so the radiator gets the first shot. Until you are confident in the numbers I would not spend a lot of time in OD. Unless you really are locking up which would explain the numbers you are seeing.

[mhagie]

I have a devil of a time getting my tranny temps up.
I an running lines from tran thru rad cooler to aux filter then to a Perma Cool remote oil thermostat connected to a good sized remote cooler.
The stat is supposed to by-pass the remote cooler until temps reach 180*.
The highest temps I have seen is about 160*+ on a 90* day.
The temp gauge is installed 3/4 inch above pan bottom on the side of a B&M deep sump tranny pan.
I could repipe it so oil goes thru remote filter then radiator as it has a temp port in the top.
I was tempted to by-pass rad altogether but was afraid I would have even more trouble getting temps up.
Merle

[ZZ]

Originally posted by twaddle:
Hi ZZ,
Generally the temperature pick up sender should be located so that it picks up the oil temp at the torque convertor outlet, as close to the convertor as possible.
This is always the hottest point of the transmission.

Regards

Jim Twaddle
Biggar, Scotland I have the temp sender inline just after the external filter. It doesn't seem the fluid temp would drop very much between the tranny and the external filter after it gets up to normal operating temps. I could be wrong though ;)

I drove it yesterday on a 60 mile round trip. The TC stayed locked up for 10 miles. The temp was running around 110. Then the TC lock dropped out and then it warmed to about 135. I don't think I'll see much higher temps till hot summer.

[DmaxMaverick]

I don't think you are getting accurate temp readings. It may be linear with the actual temp, but it's off considerably. Way too cool, probably in the neighborhood of 50

[twaddle]

ZZ,
Without seeing the set up with the external filter and the pipes or hoses going to and from the oil cooler it's a bit difficult, however it looks like you may be getting temperature readings of the oil as it returns to the transmission from the cooler.
This would be the oils coolest temperature compared to any other point.

The temperatures you are getting are around what I would expect after the oil has cooled especially if you have a slightly larger that standard cooler.

The hottest point to read transmission oil is AT the connection where the oil leaves the torque housing. Unless you have slipping clutches the torque convertor outlet oil will always be the hottest point and this is where the sensor should be.

Is there any way that the line that the temp sensor is onto is actually the oil return from the cooler?

Do you know anyone with an infra red temperature reader that could check which pipe, hose or connection is the hottest after the truck has been driven, it would need to be tested as soon as the truck became stationary.

Regards

Jim Twaddle
Biggar, Scotland

[Robyn]

A 700 set up to run without a lockup is done all the time. You need to use a special built non lockup converter and you also need to change the valve body slightly. This entails changing one valve to correct the oil flow without the lockup.
Been there done that.
Without the proper stuff burnup can and does happen.

[ZZ]

Originally posted by twaddle:
ZZ,
Without seeing the set up with the external filter and the pipes or hoses going to and from the oil cooler it's a bit difficult, however it looks like you may be getting temperature readings of the oil as it returns to the transmission from the cooler.
This would be the oils coolest temperature compared to any other point.

The temperatures you are getting are around what I would expect after the oil has cooled especially if you have a slightly larger that standard cooler.

The hottest point to read transmission oil is AT the connection where the oil leaves the torque housing. Unless you have slipping clutches the torque convertor outlet oil will always be the hottest point and this is where the sensor should be.

Is there any way that the line that the temp sensor is onto is actually the oil return from the cooler?

Do you know anyone with an infra red temperature reader that could check which pipe, hose or connection is the hottest after the truck has been driven, it would need to be tested as soon as the truck became stationary.

Regards

Jim Twaddle
Biggar, Scotland I believe the line I'm using is the output line from the tranny. It is the one that went to the top inlet hole in the radiator. I cut the line about 8" from the radiator inlet. I have a hose running from that line to the external filter mounted just behind the passenger side battery. The other hose runs from the filter to the radiator cooler. The lower line out of the radiator runs up front to the cooler which is mounted behind the grille. The fluid goes out of the cooler back to the tranny. I'm certain that I have it plumbed right.

[CleviteKid]

The GM Shop Manual indicates that the LOWER port on the radiator is the INLET from the tranny, and the UPPER port is the OUTLET from the cooler. If your engine thermostat is not opening, the water in the radiator could be near ambient temperature, and your apparent fluid temperature could be near ambient, upon exiting the cooler.

Most liquid heat exchangers feed from the bottom, thus the entire cooler MUST be filled with liquid before it can come out of the top. If plumbed backward, the liquid could just fall through the cooler and out the bottom without much chance to exchange heat with the opposing fluid.

On the 700R4 there is a pressure tap on the driver's side of the case, above the shift lever. This is at the output from the internal pump, and represents the highest temperature before being sent out to the coolers and external filter (on my truck). This is where I put the pickup for my tranny temp gage, and it seems to read like it should, 160F just cruising, and 200F if I am pushing it.

Dr. Lee :cool:

[ZZ]

Thanks Dr Lee. I guess I need to do some rearranging on my plumbing. I guess I've been wrong for many years about the fluid routing.

[ZZ]

I moved the temp sensor to the bottom line today. It does show a little more heat on the guage around town. I'll know more Friday when I make a 200+ miles round trip.

I may need to re-route the lines later. The way the fluid runs now is out of the tranny to the external cooler, and then through the radiator and to the external filter and then back to the tranny. It seems to me that it should go through the external cooler last.

[Barry Nave]

Dr. Lee, does this hold true for the 4l80E also.
Been asking the same question on the 6.5 forum.
Most still think the top port of RAD. is the inlet.
Let say on my 95 the routing would than be,
From TRANS to in front of rad. cooler, to lower port of rad inlet,from rad top port back to Trany. This is what your saying?

[Barry Nave]

ZZ Your not alone on this :D
My lines have never been changed. What I'm trying to figure out is the flow path.
I have a inline filter from NAPA that is spliced into the EX. cooler.
This line is going to trany or from trany.
The filter has a arrow showing flow and need to figure out if I have it in wrong.
What DR.LEE is saying I than need to replace the filter and change the arrow pointing the other way. My filter is pointing back to trans from the EX. cooler. So this would be backwords. :confused:

[ 01-19-2006, 01:21 AM: Message edited by: Bnave95 ]

[ZZ]

We had line heat today. I had an unexpected 60 mile round trip to my Doctor today. (Still falling apart).

Anyhow, the temp was running around 105 till the convertor kicked out after the normal 10 miles of highway miles. It warmed on up to 160 for the rest of the trip. On the way back I was facing 35 mph gusty winds. The temp ran about 180 all the way back into town. It cools down fairly quickly in town driving. I'm scared to imagine how hot it ran on the hot days of last summer.

I think I finally got things where I can really watch the tranny's true temp.

I'm fully convinced that the bottom line is the output from the tranny. ;)