Transmission and engine temp questions

[jandersinc]

When I tow my ~9,000 pound boat in hot weather (100 F ish) I've seen 225 for both the engine and transmission on several occasions up steep hills at freeway speeds, but they'll drop to about 210 for the engine and 200 - 210 for the transmission after cresting the hill.

 

We should have the same engine / trans combo I believe although mine has the all aluminum 6.0, not sure if the 2500 HD's do. 2500 HD's might have an iron block 6.0.

 

I have the 6L90 transmission and 3.73's.

[dsblue2000]

I agree with Jake111, the dash temp gauge is at best optimistic, at worst just plain VERY slow to respond. I installed an aeroforcetech scanner and watch the engine temp pretty closely. On a recent trip, according to the scanner, the engine approached 230 (very briefly on a very steep stretch, running in 2nd, towing our 5,000lb TT - any higher and I would have pulled over, I think) and the dash gauge still read slightly under the 210 mark. It does seem to eventually catch up, but it is VERY slow to do so. I've seen the gauge on a few instances go a couple marks above the 210, whatever that means, but that was before I had a digital gauge. Maybe I was happier before I really knew... ;)

 

As for trans temps, my manual says 180-200 is "normal operating temperature". I had a similar discussion with a local GM trans tech and, when I mentioned reaching a trans temp of 220, he said something to the effect "you don't start to burn (transmission) oil until 250 or so". It could have been 260, I don't remember so good sometimes. Either way, the 220 wasn't considered alarming. Anything over 200-210 is fairly rare for me, even towing, now that I replaced by 3.42 gearset with 4.11 (a much better towing machine now).

 

I don't know if any of this is helpful or not, but it's the what's what with my setup...

[dsblue2000]

Follow-up post - I took the unusual (for me) step of actually looking in the manual. It actually has numbers on the Engine and Trans temp gauges page. For the engine temps, paraphrasing, it says 210F is normal for most driving (as many of us have seen). It further says it is "normal to approach 250F" on long grades, etc, but at 260F "the cooling system is working beyond its capacity". I love the phrasing.

 

Personally, seeing how dreadfully slow my in-dash gauge is to catch up to actual temperatures, if it ever "approaches 250" it's way past that by then. Dex-cool boils at 265F at 15lbs of cap pressure, if I remember right, and there's probably steam by then. Anything over 220-230 on my scanner and I plan to change something pretty soon if I'm not near the top of the hill, or whatever is pushing it that high.

[markw8]

220-230 won't hurt a thing as long as it drops back like it should. Corvettes from the mid 80s on this is normal in traffic. The second fan doesn't come on untill 235. The first about 227.

[dsblue2000]

OK. Food for thought. Maybe I'm just overly sensitive to it.

 

It just seems like this particular truck has an excellent cooling system and on those rare occasions when temps reach this high it just goes up and up and only drops back down when we're over the grade. I have waited for the fan(s) to come on and I can't detect it happening. Maybe it hasn't gotten hot enough. If anyone knows when the fan(s) come on for the 5.3L, I'd appreciate knowing. Thanks.

[ATMINF]

I have a scanguage and it tells me the actual temps. On the last couple of hot days(in the 90s) the coolent has goten to 197 then drops back down to 193, and the hottest the trans has gotten is 170+. The is just stop and go traffic about 11 miles and never getting about 45-50mph, also the drive takes about a hour long. So I do alot of sitting then creeping along then short bursts of speed. Also my truck has the 6L gasser and 4L80 trans.

[sdeeter19555]

I have a scanguage and it tells me the actual temps. On the last couple of hot days(in the 90s) the coolent has goten to 197 then drops back down to 193, and the hottest the trans has gotten is 170+. The is just stop and go traffic about 11 miles and never getting about 45-50mph, also the drive takes about a hour long. So I do alot of sitting then creeping along then short bursts of speed. Also my truck has the 6L gasser and 4L80 trans.

 

 

 

I have an Edge Insight, and see about the same...even towing what I believe was around 6500#s in the mountains netted me just a tad over 170*F on the trans (the engine never seems to climb above 205*F).

 

If you can see the torque converter operation, you can actually see its locked up most of the time, even when shifting up and down. About the only time my 2012 2500HD unlocks is coming to a stop and very, very, rarely under a loaded downshift (and then only a brief second).

[t?m]

Traveled across Maryland/WV via I68 last week. Never saw the engine temp move from its constant 210. Highest transmission temp was 201. There was only one grade I couldn't maintain 60mph and that probably was because I got blocked by traffic and had to slow down for the initial climb.