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My C6 is hitting 210(F) in regular highway driving, and 230(F) in cities after highway trips.
The stock in-the-radiator cooler was not enough. A 10x21x1.5" aftermarket cooler with 10" fan is not enough.
I'm starting to wonder if the transmission has a problem. It shifts fine with no noticable complaints. Fluid is type F as I think the transmission is a 71 truck model, though the truck is a 77.
Is there a way to test for slipage? Are there specs for pump flow rates or pressures? What could be the problem?
I realize you have a fan but where is it mounted? Also, is the aftermarket cooler before or after the stock radiator/tranny cooler? Where is your sending unit mounted? When was the last time the tranny fluid was replaced? Is it bright red or brown? Does it smell burned? That's all that I can think of.
It's mounted right about there! It basically spans the gap between the radiator and crossmember. There's a 10" puller fan on top. The cooler is aftermarket, and the stock cooler is not in the loop anymore. The sending unit is mounted near the transmission in the outlet to give me the hottest temp the fluid hits. Fluid(type F) is red, and might have the slightest smokey smell. Not sure on that one. It's about 6 months old.
Might be the gauge/sender. Mine always reads hotter than it should. I took it off and rigged it up in a pan of boiling water and compared with reading from wife's professional grade meat thermometer. If you test this way, make sure the therm. and sender are not touching bottom of the pan. At 212 deg. F. on meat therm. my gauge reads about 230 deg. F. In my case, I'm pretty sure I have a water temp sending unit on a trans. temp. gauge.
Last edited by Piffery1; Apr 26, 2006 at 01:26 PM.
Reason: spacing
I have not tried testing the sensor... good suggestion. I was assuming that since I had two of the same they ought to be calibrated the same... but there's no guarantee I guess. I'll do that tomorrow morning.
OBTW, on my '83 F350 w/460 and 4-row radiator and 195 deg. F. thermostat, after initial warm-up the trans temp never varies by more than 5 deg. F. in town, 65-70 on highway, loaded or empty and the stock coolant temp gauge stays right in the middle of "Normal". It does have the additional trans cooler mounted in front of the radiator (which I think is original equip. on all 460's).
Last edited by Piffery1; Apr 27, 2006 at 12:59 AM.
Reason: add
The problem with factory guages are that they are often designed to give good appearing readings rather than correct ones. Like fuel guages that stay on full for 1/4 tank, temperature guages that dont waver until it's too late, oil pressure guages that indicate normal pressure anywhere between 10 and 120 PSI, etc. Keeps people from complaining about their car running too warm etc. Ok, heading out to play with my gas guzzler. I'll let you know how the temperature thing comes out.
If I remember the haynes manual correctly during the rebuild of my C6, it stated that the normal operating temp was close to the engine operating temp if not higher. So, 200 degrees F should be mid range of the normal operating range. Also, Haynes suggested that an aftermarket cooler be installed after the radiator cooler to aid in warming up the trans to operation temperature. If everything else seems normal and the trans is not having higher shift RPM then I would think your transmission is operating normally.
I put a large scoop under my truck to push lots of air through the trans cooler. top temperature dropped to 200F, though it's only 68F out right now so that might not be a fair comparison. I'm getting an infrared pyrometer(digital laser thermometer) to test the trans temp, figure out why the floor boards get hot, and I hear you can tune with 'em.
IMO, I think your problem is inadequate air flow. I have an electric fan mounted on the front of my radiator, with the tranny cooler sandwiched in between. When I'm going down the road, the temps drop considerably and I can cruise in really hot weather with it hovering around 160-170, or so. When I have to keep stopping, it climbs up, sometimes around 190+. I turn on the electric fan and it helps, but not much. If I were you I would mount that somewhere that will allow air to flow through it as you are driving down the road.
I don't have the AC condensor in place yet... I suppose I could test that theory fairly easily. I really appreciate y'alls continued help and patience.