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Old 09-11-2019, 04:15 PM
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Temperature gauge on Turbo 350

Hello guys I had my Dad install a b&m transmission temperature gauge for me while he did my cam swap for me and I am running a turbo 350 with a 3000 rpm stall converter with an external transmission cooler right in front of my radiator and I got the recommended size that Hays recommends and on the b&m instructions it says to install the sending unit on the return line from the cooler but while checking things out as I got my truck back a few weeks back I noticed my Dad hooked the sending unit on the output line of my turbo 350 line that is going to my cooler to get cooled.

Now I am no transmission expert and never had a temperature gauge on one before so please bare with me but I am a little worried my transmission is running to hot but I don't know for sure when I first start driving it is around 170 degrees to 180 but after a lot of driving in town and stop and go traffic and my under hood temperatures being pretty hot and with it being a 96 chevy s10 v8 swap its pretty compact but anyways my temperature gets up to about the right at beginning of the yellow area on my b&m gauge but my transmission works good and nice and strong and shifts excellent. My question is my transmission running to hot and should I be worried or am I ok? With it not being on the return line like B&M recommends I don't know how much the cooler is cooling the fluid and I also have seen where people have gotten gauges that go into the transmission pan drain plug if using an aftermarket aluminum one like I have. I know higher stall converters will make more heat but is my transmission not going to last long like this or am I just panicking for no reason. Thanks guys and much appreciated for any responses.






https://www.summitracing.com/parts/bmm-80212/overview/

https://www.holley.com/products/driv...parts/97-1B28Q

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Old 09-11-2019, 06:26 PM
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Temp sensor needs to be in the pan. Not on the cooler lines In or Out..

the "out" line of the cooler lines can run much hotter than the transmission is actually running temperature wise
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Old 09-11-2019, 08:07 PM
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I am not going to take my b&m gauge out but I have an aluminum pan on and I know you can buy gauges that will allow you to use the temperature sending unit as a drain plug but I also know you can get ones that has a 1/8 npt that can be put in the side of the transmission and there seems to be a lot of arguments on where to put the gauge sensor at. I don't mind buying a second gauge to put on my truck as for me the more the better to keep track of things. I have a spare turbo 350 I am going to learn to build and educate myself on but I want to keep things going as for as long as I can while my truck is solid.

I have read positives and negatives on the temperature sending unit on the pan as if the transmission overheats real quickly the cooler lines will register more quickly then the oil pan but I don't know how much truth is to that as I have only been watching videos on rebuilding turbo 350's and I want to keep mine current one going good as long as I can.
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Old 09-16-2019, 06:37 AM
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You dont want a plug/sending unit....total PIA....the sending unit should be in the pan, usually the rear area. Pan must come off, drill and tap 1/8" NPT and install. Move current sending unit wiring to the new sending unit. You will see the temps fine if it starts to heat up. The return dumps to the pan then the pump pulls from there. Had this on several high powered vehicles with no issue. You want the temp of the mix of fluid in the pan, not whats coming from cooler.

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Old 09-16-2019, 06:50 AM
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Quote:
Originally Posted by BigMo View Post
You dont want a plug/sending unit....total PIA....the sending unit should be in the pan, usually the rear area. Pan must come off, drill and tap 1/8" NPT and install. Move current sending unit wiring to the new sending unit. You will see the temps fine if it starts to heat up. The return dumps to the pan then the pump pulls from there. Had this on several high powered vehicles with no issue. You want the temp of the mix of fluid in the pan, not whats coming from cooler.

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This ^^^^.


And, a temperature gauge that has full markings on it would be a bit better than a guess. I also disagree with the size of the cooler - it should always be the largest thing you can find room for - running a trans a touch cooler is never going to hurt it on the street. On our third-gen Camaro, we have two coolers on either side of the radiator so as to keep them out of the air flow for the radiator. I mount the senders in the trans pan on the passenger side, about 3/4" from the bottom and 2" from the back.
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Old 09-16-2019, 07:00 AM
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I already have an aluminum aftermarket pan on my transmission that has a drain plug and there are many gauges that have adapters with them so you can screw them in right there but the only worry I have is how far would it stick out and would it cause a clearance problem. Yes I can just drill on the side of the pan and drill it a 1/8 npt and just get a gauge that would plug into it and I might look into trying that idea as I do have a drill press and and can use it to get a better drilling into it vs doing it by hand. I am not the best driller in the world when doing things by hand as I am very green still when it comes to that.

There are so many arguments on location of a temperature gauge on which is the best spot. I will just install a second gauge and have two of them going in two different spots. I will leave the one on the line and I will get another one on the pan as much as I can if not then the port on the side of the transmission if I can't get it right but I should be able to do that as its not that much of a rocket science job just a basic skill of drilling and tapping.
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Old 09-17-2019, 06:30 AM
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Just curious if you ran the coolant line through the radiator cooler first and then the external cooler? That's the way to do it.


The feed line to the coolers is the hottest place to measure because it comes straight from the converter where 90% of the heat is generated. You are measuring the converter temp not the transmission temp. So expect a gauge on that line to be hotter than the engine coolant, hopefully closer to the engine coolant coming out, then cooler yet out of the auxiliary cooler.
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Old 09-17-2019, 07:21 AM
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My radiator does not have a hookup for the transmission cooler lines as its a aftermarket aluminum rad that did not have them. I am running my cooler straight in front of my radiator with about a two inch space between it and is right in the flow where the air will flow through the best and also you can still feel my mechanical fan pulling air through it in park so I know its getting good flow while I drive as my engine temperature shows that.
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Old 09-17-2019, 08:19 AM
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Quote:
Originally Posted by 55 Tony View Post
Just curious if you ran the coolant line through the radiator cooler first and then the external cooler? That's the way to do it.
This is an idea that I have had a problem with since day one. The OP doesn't have a radiator trans cooler, so this doesn't apply to him, but if we can, I'd just like to discuss the idea as an aside.

The transmission is said to operate normally when the fluid temperature is about 170/180 degrees. I contend that if you run the fluid through the radiator cooler first and remove some of the heat, so that the fluid temperature is roughly 170-180 degrees, then run the fluid through an external cooler and lowering the fluid temperature to something less than 170-180, you are over-cooling the fluid and introducing it back into the transmission too cold.

Common sense thinking would take the fluid out to an external cooler first, removing the heat from the fluid down to below what the best operating temp of the fluid is. Let's say that maybe the external cooler lowers the temp of the fluid to 130/140. Then we would run the fluid through the radiator cooler to add some heat back to the fluid to bring it up to the optimal operating temperature of 170/180. Doesn't this make more sense than introducing cold fluid back to the transmission?

Please just think about this for a bit before you come back with a knee-jerk reaction.
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Old 09-17-2019, 10:21 AM
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Tapping the gauge sender into the oil to cooler outlet gives the highest oil temps you'll see. I always do this at the minimum afterall the max temps have a large effect on oil life even if seen briefly. By themselves these numbers can be scarry but in general the sump temp is what most people and the manufacturer's recommend monitoring.

By using an electric gauge with a switch and three senders I can monitor feed out to the cooler, cooler return, and sump as I choose to. seeing the corrolation of my personal S15 with 350 and 700R4 your outlet temps are comparable to mine. My sump temps when the output monitor is showing 220 is 170.

On the interstate it takes about 30 miles of open highway at 75/80 mph to get the outlet trans temp to 180 and steady. This being in Puget Sound where the air temps except in July and August are mild low 70's down to freezing in winter. In stop and go traffic on the interstate the outlet temps get up to 200. In heavy city traffic on a hot day with long stoplights sometimes requiring 3 to 4 rotations to get through them the outlet oil temps will go to 240 with pan temps at 200-210. Obviously it gets super hot in city rush hour traffic. Topography is hilly to mountainous.

The trans is built with a lot of Sonnex and TCI parts, Raybestos clutches, Kevlar band, case saver, Beast sun shell, etc. with a 3000 stall converter. It was originally built to race but with an engine change from a carbed LT4 to moderatly built up Vortec block it became the shop truck and my daily driver. The trans stayed the same as originally built to go racing. I run a ATI 0W-8 synthetic Type F in it. You know it when it shifts, nothing subtle about it.

Your temps off the cooler outlet appear to be what I'd expect to see.

Bogie
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Old 09-17-2019, 10:22 AM
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I think there is a difference between the transmission operating at a normal temperature versus one that is used in a high performance situation.



In different terms, on my RV or tow truck I would route an extra cooler as you suggest - removing the bulk of the heat then running it back through the radiator unit to be at the "factory" temperature. And as long as that temperature was maintained, I would say mission accomplished.



But on a performance vehicle, my personal preference is to completely avoid the radiator cooler and keep that fluid as cool as possible. High performance driving will heat the fluid quickly and I would certainly not want to give it any additional heat.
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Old 09-17-2019, 03:24 PM
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Yeah i am going to get a second guage to hook up to a different location either at the pan or the side where the pressure port is and have it there and leave my other one where its at as well and just run with it being two temperatures and thank you for the new info that helps me to not freak out so much on the temperature I am seeing so far.
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