Thinking about buying a 2009 TK. 40,000 hours

Unless you run all icecream you don't need the big unit. I haul quite a bit of frozen, including icecream from time to time, and I have a C600 and it does just fine.

 

My tk 200 runs 0 in 90* weather just fine for the regular frozen processed junk I usually haul, I don’t think I’d try ice cream with it in the summer though, it’s a 2011 that I got with 14k engine hours for 19k I think it was, still had to do this that blah blah blah, I like old trucks for simplicity, but trailers a wear point that actually makes the money and I’ll never buy another used one again.

 

Yes, have a 2018 Great Dane with a TK C600. However I do think in hot temperatures like 100 the age of the trailer pays a part. Also FYI a C600 is the old SB230

 

I've heard the s700 described as overkill, and when I was pricing out used ones, I found little difference in resale price despite there being a significant upcharge for a new one. This would suggest that the market agrees with the s700 being overkill, and therefore the market isn't willing to pay a lot more for it.

Plus it runs at higher rpm, which theoretically means fewer operating hours before repair. The 600 series runs at 2050 rpm to get 33 horsepower whereas the s-700 uses 2600 rpm to get 35 horsepower. The difference in BTU is bigger, 25000 vs 20000 cooling at -20 in 100 degree ambient temp, so that's a 25% difference. The c-600 actually does a little better than the s-600, putting out 21000 btu for a difference of 19% vs the s-700.

Whether the difference in BTU will make a worthwhile difference in holding -20 will be a function of the insulation package of the box, and how degraded the insulation is. Any maker's full insulation package in good condition should do fine holding -20 with any of the above models. The "step down" models will take quite a bit longer to cool down though, like maybe twice as long, like 2 hours instead of 1. So you've got the drawback of higher rpm's being offset by the benefit of less run time.

Best personal comparison I can make is my x4 7500 also rated at 25000 BTU, having absolutely no problem at all with frozen temp on my Wabash Arcticlite despite the insulation having been compromised by two rows of recessed etracks. I was amazed how effortless it is. As far as older ThermoKing models, the sb-210 and 230 were rated at 21000 BTU and the sb-330 was rated at 25000. So ghe new series give same performance with newer guts, theoretically more fuel efficient but also costing a bit more for pm's.