Best place to measure Alli Temp?

[chuntag95]

I currently have the factory gauge that is in the pan and a Wal-Mart cheapy stuck in the cooler fins. The two don't track too good. I am sure the factory gauge response is a little slow. I have also read about the temp going into the radiator being lower than the temp coming out. It this is the case, then you will hit the 195 regardless of the cooler improvements, etc.

So, where do you folks have your probes and what are your using? :confused:

How can we get this thing to run at 160-170 all the time?

Do we need to bypass the radiator and put in a second cooler?

Do we need to set put thermo control valve that bypasses the radiator when the fluid hits 180?

I have a fan controller that will keep from turning the fan on till it warms up, but if you remove the radiator from the loop, you remove one of your warming methods.

Do we put in a bypass that can be switched for summer and winter?

What do all of you boys and girls think?

I don't want to cook this thing sitting in traffic and I hit 210* almost daily with this 100* heat. The additional fan keeps it to 195 but that's not a whole lot better. I love a good bar-b-q just like the next guy but really would prefer it not be my Allison. :(

[DmaxMaverick]

I would not recommend taking the radiator coil out of the loop. The tranny coil is in the "cold" tank on the radiator, and will be considerably less hot than the thermostat temp, below 160

[Gbenzx01]

chuntag,
Your Allison is certainly doing some things that ours & others are not doing. If the black nsbu switch has not been changed out you should be able to get dealer todo this. If you are not thru the 2nd transynd swap I would do this now even if mileage factor has not been reached.
Above all get to an Allison shop & they will take a ride with you if necessary. Chances are they will find the problem immediately if not sooner.
These people too can call your service manager & get you a new allison if necessary. Most GM service managers will not call them but will certainly listen to their advice. Filter may not be factor but change anyway, just 2 sense but maybe. Just my guess but really believe you may need new transmission.

Gben

[a64pilot]

Chris,

Your Allison is certainly doing some things that ours & others are not doing I second this. In 97 deg. weather, pulling 20,000 lbs. in town mine didn't quite reach 200. I'm pure stock drive line BTW, no Transynd yet or deep pan.
Hound them while it's still under warrenty, go to a diffrent dealer.
Allison cannot warrenty our trannies, I believe the warranty is through GM. But if you don't mind too much paying for a good diagnosis, they would be the ultimate subj. matter expert.
I'm afraid that if you modify the cooling system then you'll inherit any pre existing problems you have even though a reasonable man could see your mods would only have helped, not hurt.

[mackin]

chuntag95


First thing I would do is When it's 210* go to the dealer have them plug in a Tech II and check accuracy of the cluster gauge .....If it is accurate it is with in operating range ..... Higher then most I've seen nevertheless .....

The factory gauge gets it's reading from the top of the pan ....

My Autometer sending unit is mid ship in the deep pan .....

The factory gauge reads higher could be do to the closeness to actual parts retaining heat ...... See below ....

I've noticed that the Autometer gauge temp drops quicker once moving after sitting in or driving in traffic ..... ;)


I have never seen factory gauge over a deuce ..... Hot and sticky , 2 ticks below hauling azz .... Seen this on "two" cluster ....
The best place would be (to get a reading) would be from the "From cooler line " I believe ......
Good luck and let us know what happens .....

Mac http://forums.thedieselstop.com/ubbthreads/images/graemlins/shrug.gif

[ 07-25-2003, 08:16 AM: Message edited by: mackin ]

[chuntag95]

I just took it in and they couldn't find anything. I guess I can find a different dealer and try that or get it really hot and take it back to them and have the tech ride it right then. There is an Allison dealer in town, so I guess I could see what the cost would be to have them check it out. I need to go and get some more filters and some Transynd anyway. I was going to look at the deep pan stuff then as well and try a second flush. I have been changing my spin on filter every 7.5K.

My biggest problem is sitting in traffic when it's hot. Running down the highway is no problem. The reason I was asking about location and stuff is I am not sure the factory gauge is correct. I have not been about to find something I could put down the dipstick tube or something like that. If it says 210 and it's really 195, then I am worrying for nothing.

I got my second fan put on last night. I toasted the first one trying to turn the blade over and make it a pusher. This one went much more smoothly. We will see how it does on the drive home tonight. It is mounted in the center of the cooler and when you look at it, it's behind the center bar on the grill. I had to make a replacement support for the center of the grill to be able to center mount the fan. It wasn't hard, just bend a little 1/8" steel bar and put the clip on the end. I have not been able to get the temp controller to work the way I think it should, so I am thinking I need to send it back and bet another one. :rolleyes:

[chuntag95]

Mac,

Thanks. In your pictures, you have 2 lights over the airbag switch. What are they for?

[77TransAm]

chuntag95 - a couple of things come to mind from your post. First, the factory gauge is displaying sump temperature as measured on the Pressure Switch Manifold on the valve body. The temperature of that volume of fluid is not going to change very quickly, whereas the fluid in the cooler that your other probe is measuring is coming from the converter out circuit. That fluid temp is going to change very rapidly, depending on how much the oil in the converter is being sheared at any given moment. It should also be much hotter than the sump temp at most times. I would guess that this is the reason your two gauges do not track consistantly with each other. The sump temp thermister is typically quite accurate, although the factory gauge leaves a bit to be desired. By chance when you took it in, did they put a Tech II on it to see if the gauge is displaying the same temp the thermister on the PSM is seeing?

Second, since the engine comes up to operating temp much faster than the transmission, the water in the radiator will be warmer than the oil until the trans gets up to temp. Once all temps are in the normal operating range, though, the radiator tank does remove a substantial amount of heat from the transmission fluid.

Finally, if you're seeing 210 only at idle, more air is probably not going to make a huge difference. Idle cooling flow seems to be a delicate balance with the Allison. If they leave a big enough passage to provide plenty of cooler flow at idle they run into priming issues at startup. Tighten up all the clearances to fix priming and there isn't enough cooler flow at idle. They seem to have it worked out pretty well, but yours does sound like it runs hotter than most. It may be at the low end of the spec for cooler flow, which would cause it to run at the high end of the spec for temperature.

On edit: just to stay on topic, the best place to measure sump temp depends on what you're using to measure it. If you have thermocouple probe you can either drill and tap the drain plug in the pan or drill and tap the plastic plug in the unused dipstick hole on the driver's side. If you're using a larger sending unit you will probably have to install it into the side of the pan.

[ 07-25-2003, 02:12 PM: Message edited by: 77TransAm ]

[chuntag95]

Originally posted by 77TransAm:
Once all temps are in the normal operating range, though, the radiator tank does remove a substantial amount of heat from the transmission fluid.

Finally, if you're seeing 210 only at idle, more air is probably not going to make a huge differenceI thought I read that someone had a gauge reading transmission fluid temps going in and out of the radiator and the radiator was adding heat. I have not confirmed that, but the statement concerns me. It would make sense if the temperature of the coolant is 195* and the transmission is 160* going in. I don't know what the gradient is on the radiator or what the temp is at that level at operating conditions.

I have the scoop to get air into the transmission cooler, but when you are not moving, it doesn't work well. That's where the fan idea came from. Today at lunch, the temp was around 195 with the fan running at 95* outside temp and the cooler over 160* (cheapy gauge won't go any higher). I have seen the cooler temp at 150* with the transmission temp over 200* without the fan so I believe it is making an impact. Not as much as I would like, but liveable. I need to run it for a couple of days to make sure that is the norm in the Dallas desert. :rolleyes: I also need to get the controller working correctly, but that is another story.

I didn't check to see if they compared the gauge to the thermistor. I like the idea of getting it hot and taking it to them to check. Just need to find the time.

[Joe.G]

First off, don't trust the factory gauge or the sending unit, they are not precise. You need to get an aftermarket quality gauge like an autometer, install it and see if you really have a problem. Mine never runs over 185 and I drive downtown Dallas everyday. Only other thing I could suggest is to change to synthetic fluid, it runs cooler, protects better, and lasts longer. If you stay below 220 degrees with the regular fluid you should be OK.

[mackin]

Originally posted by chuntag95:
Mac,

Thanks. In your pictures, you have 2 lights over the airbag switch. What are they for? Red => High Idle .....
Black => OD lockout ....

Mac

[chuntag95]

Mac,
Thanks. I was thinking about adding a light for my trans cooler fan to know when it's on, but I am not seeing the results I really want.

Okay, had to go to a wedding yesterday. We were late and I was pushing hard. I was treating the truck more like a Porsche. Anyway, earlier yesterday, I put a second cheap gauge on the outlet side of the cooler. I get to see the in and out now. I put what was the in on the out since I have an idea how it was reading. I saw there be no difference between in and out and up to 25 degrees. At one point, they were both overtemp which occurs at 158*. :( I am going to swap them back to see if the ranges stay the same. The tranny gauge was at 205* when we got to the church and that was with the fan running the whole way. Outside temp was 99*-104* according to my rearview. After the hour plus wedding, it had cooled down to 170* on the tranny gauge and 130* on the cooler after I started it. The cooler read 105* before cranking.

I am thinking my best bet is to get a good gauge and install it. Did the deep pan come with a fitting to put in a temp gauge? How do you hook up to the transmission to get the temp? Is there a port or something? Mac, Hoot, anyone?

Hoot, don't you have several sensors hooked to one gauge? How did you do that? I was wanting to get oil temp, oil pressure, tranny temp and differential temp. If I could switch the input between sensors, I could get at least 3 of those with one more SPA gauge.

HELP!

[mackin]

Just a hole drilled into deep pan and 1/8'' electric sender, 3/8'' & 1/2'' NPT fittings,that came with gauge kit ....The only time I see big swing differences is when the tranny gets HOT ....Hot as in driven for a long time,stop go whatever, in hot ambient conditions .... The factory gauge is close to the actual MASS (inards), Retaining heat longer,never cools off till it sits for awhile, therefore higher temps almost always .....


Mac ;)

[Lone Eagle]

I have seen 210 on mine a few times while in stop and go and around town towing. I don't thing there is anything wrong with the majority of our trans gauges. I think they are reading trans temps and not oil temp. The Allison is a big heat sink. It tanks a long time to cool down. There are only two ways I know to change the direction of air flow of a fan. Turn the whole fan around or reverse the motor rotation. The radiator does in fact heat the trans oil when you first start the truck but not to 195. That is the engine temp and not the return water temp. Later! Lone Eagle ;)

[chuntag95]

Would a fan blowing on the transmission case help? Since the fan on the cooler isn't helping much, maybe the answer is to try and cool the mass. I have considered putting in a second cooler with it's own fan that has a temp controller mounted in it to turn the fan on at 160* and off when the fluid is cooler. Thoughts?

[a64pilot]

Chris,
This thing is fluid cooled. I don't think the case has enough surface area to benefit much from air flow over the case. You've already tried increasing air flow over the cooler so as I see it the only real option you have now is an additional cooler. I think this cooler is a rather large pipe diameter so I think that would narrow your choices of additional coolers. I would think that Allision would make some large coolers for their motorhome bus type vehicles, maybe you could check there. Maybe an A/C condensor from another vehicle would work?
My only real experience with Trannies is with the old ones C4's C'6, turbo 350 and 400 etc. In those it seemed that slipping bands would be the source of the heat that ruined the fluid and clogged the filter that caused lower fluid pressure that led to worse slipping. That was usually the cycle.
If these trannies are like the old ones then excessive heat can only come from one of two sources, slipping clutches or overheated Tq. converter. The only way a Tq. converter should overheat is by being in a stalled condition for too long like using throttle to hold a very heavy truck still on a big hill or something.

[chuntag95]

A64,
I am thinking an additional cooler is my next choice. I have found some stacked plate coolers with a fan on them that are 1/2". They are made to be oil coolers, but that doesn't matter. I also found some 5/8" tube coolers for a dodge, but it only has 3/8" NPT fittings. Finally, there is the B&M that is 1/2" Barb stacked plate, with fan and a 160* thermal switch to turn on the fan when needed. It's a bit more, but looks like the best for this particular aplication. I am debating (with myself) on a temp gauge or just jump to the cooler. Judging by the way my temps at the cooler are about 10 degrees lower than the trans temp gauge, I think if it's off, it's not by much.

[HoustonDMax]

Chris, I tried an experiment this weekend. Swapped instruement clusters to see how accurate guages were. Tranny temp on temporary cluster was two ticks lower, engine temp was two ticks higher, voltage was two ticks lower, oil pressure was a tick lower and fuel level was lower. Shows how accurate these guages really aren't. Checked both clusters against Tech 2, and neither cluster was spot on. Go figure.

I think you are on the right path with trying to get better data before spending unecessary time.

[chuntag95]

Mel,

It sound like I need to get the gauge and then another cooler. I'm going to have to work hard on the wife to get this out of her. :( She is already complaining about the mod money I have spent.

Chris

[SoCalDMAX]

Chris,

Sorry, I just saw this thread. I've got a SPA digital gauge hooked up to a sender in the side of my deep tranny pan. The sender is submerged in fluid, but isn't deep within the tranny like the factory sender is. As mine warms up, the factory gauge and SPA gauge both go up in unison, but the factory gauge reads 25 to 40* higher, most often about 30* higher than the SPA.

I believe 77TransAm is absolutely correct about the location and accuracy of the factory sender, as well as the inaccuracy of the factory gauge. Unfortunately, I never tow in town, so I can't give you direct numbers to compare, but quite often I see 180 - 200* on the factory gauge while the SPA indicates only 150 to 170*. I believe the SPA sender and gauge are pretty accurate. I'm not sure that the side of the oil pan is the best place to mount, but the setup seems very responsive.

Assuming that my 30* offset is typical, your gauge may just be a little more "off" on the high side than average. One thing you could do to verify, buy one of the $99 IR temp guns. They read out in 1* increments and are very accurate. Shoot that at the side of the tranny next time you feel it's getting too hot. If you can prove that it's off by 30 or 40*, then I would think you could get the dealer to replace it or try to adjust it (if possible.)

Regards, Steve

[chuntag95]

Steve,
I have an IR gun, but didn't think about shooting the pan. I'll try that. Thanks for the idea.

Did you see my switch question on the other thread?

I think with switches, I can talk the wife into one gauge and an extra sensor or two (or three). :D