2005 Chevy Colorado Oil Pressure

TONY T

MEMBER
2005 CHEVROLET COLORADO
5 CYL
2WD
AUTOMATIC
45,000 MILES

I added an auxilliary pump to ciruculate the tranny fluid when I tow my truck behind my RV. I want to not have to unhook my driveline everytime I tow it. I want to make sure it's working before I take it on a trip. So, I bought an electric oil pressure guage with a sending unit. Hooked up the sending unit on-line to the radiator coolent line. Then, I hooked up the guage to it to test it. I'm getting no signal to the guage. What could I be doing wrong. Mind you. This temporary connections are just that. Temporary for now.

3 Replies

PEAR69

MECHANIC
1,482 POSTS

The only way to circulate the tranny fluid it to rotate the tranny pump. To rotate the tranny pump, you must rotate the torque converter. An aux. Pump will not pump any fluid through the tranny. Even if you could do what you are attempting to do, it would not "protect the tranny" in anyway. Transmissions are designed to be rotated from the front -- not the back, and in doing so, you will cause serious damage over a very short period of time.

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Monday, September 14th, 2009 AT 3:08 AM

TONY T

MEMBER
2 POSTS

Thanks for your answer. I'm confused, however. Remco sells a kit that is suppose to solve the problem. It's rather expensive ($850), so I rigged up my truck using the same principle and design for a lot less (so far I have about $350 invested). Their idea is that you run the auxilliary pump from a line you add to the bottom of the pan and with a 3-way diverter, you control the the flow of the fluid either from the tranny pump, or the auxilliary. Are you saying that it's a bad idea and it won't work? I also understand that race cars use the same principle as Remco in order to add additional circulation and keep their tranny and rear-ends cooler. I'm not a mechanic by any means and don't want to ruin my truck. Have you got a better idea, or am I just stuck with the option of having to disconnect the drive-line, or tow it backwards on a dolly? Tks.

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Monday, September 14th, 2009 AT 12:43 PM

PEAR69

MECHANIC
1,482 POSTS

An racing transmission does need to have an aux. Pump to flow more fluid, but the engine is running, therefore the trannys pump is rotating. These type of aux pumps do flow fluid faster through the system, but when the engine (or whatever turns the tranny) is not rotating the trannys input shaft - then the fluid flow is useless - meaning it will not apply pressure to the appropriate internal parts. A transmission works by transferring torque from the engines crankshaft to the rear wheels. It does this either by a manual clutch and pressure plate(manual trans) or a torque converter(auto trans). The torque converter rotates on the input shaft of the transmission. It has internal turbines that apply fluid pressure - at certain times - to the friction plates of the transmission. These turbines must "rotate" inorder for the transmission to function. The only other way to apply pressure to the friction plates is to remove the torque converter -- which makes no sense in your application.
In order for you to tow a vehicle-with an automatic transmission (without destroying the tranny) - and have the wheels rotating on the ground - you must remove the drive shaft.

BTW - I understand what you are trying to do -- "flow fluid through the tranny". Even if you do get pressure, it will not prevent damage to the transmission when you leaving the drive shaft connected.

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Tuesday, September 15th, 2009 AT 4:45 AM