I've got a permit for 5 days and 4 nights on the White Rim Trail at Canyonlands - Island-In-The-Sky for next April and May, so we'll be loading up and towing our ~ 3,000 lb A-frame trailer, 4 people, and a mountain of crap from Seattle down to Moab for some red dust, sunshine, hiking and wheeling, and tranny-cooking temps. Recalling that on a cool day last September going over a pass in the Cascade Mountains east of Seattle, we flirted with ATF temp of 235 degrees on the ol' ScanGauge, so I picked up a B&M 70264 cooler. It's somewhat irritating that Toyota touts the 5,000 lb towing capacity, and then conveniently fails to mention that if you're towing a heavy load / towing up a hill / the ambient temp is high - chose 2 of the 3 -you'll overheat the ATF. Anyhow, I need to get off my fat fundament and get the tranny cooler installed, but have a couple of questions/concerns.
1 - The hard lines from/to the tranny are 3/8" OD, but the cooler has 5/16" OD in and out fittings. I got a couple of copper 5/16"-to-3/8" adapters (
JEGS Performance Products 15946 JEGS Brass Barbed Hose Connector), and am thinking of using them near the cooler fittings to step the hoses down from 3/8" to 5/16", since I don't really want to use 3/8" hoses on 5/16" fittings or 5/16" hoses on 3/8" hard lines. Agreed that this introduces some additional potential points of failure, but I think I would rather have 6 clamped joints with properly-sized hoses than 2 clamped joints with improperly-sized hoses. Has anyone run into problems using 3/8" hoses on 5/16" fittings? Another concern is that the ID on the 5/16" sides of the adapters is about .025" smaller than the ID of the cooler fittings. I was at home sick the day they talked about both computational and finite-element fluid dynamics, so am wondering if anyone has ideas about (1) the wisdom of skinnying down from 3/8" to 5/16" on the cooler in the first place, and (2) skinnying down the ID's even further if I decide to use the adapters. One would assume that the reduction in ID would force the fluid circulation pump (or whatever it is) to work harder, and speed up the flow but decrease the pressure. Any knowledgeable fluid-flow heads out there with ideas about what to worry about - cavitation, supersonic speeds, Bernoulli and all that? The change in ID's in the adapters is a sharp step rather than a smooth venturi, if that matters. And my wife says that I over-think stuff!
2 - The consensus around here seems to be that the ATF should exit the tranny, go through the standard ATF cooler section at the bottom of the radiator, then through the auxiliary ATF cooler, then back to the tranny. On the tranny, I see the ATF outlet and inlet fittings and hard lines but it's not clear which is which. Someone posted that the tranny outlet line has a splash of pink (hot) and the tranny return line has a splash of blue (cold) to indicate which is which, and I have these marks where the hard lines transition to the rubber hoses part way up the side of the radiator, but where they transition below the alternator
both are marked with blue splashes. So much for that theory - guessing that they are a QC signoff. Someone else said to just feel which line heats up first, and I tried that (at the tranny fittings and at several points along the hard lines and hoses) but couldn't feel enough temp difference to be sure. Looking at the passenger side of the tranny, the bottom hard line fitting is below and a bit behind the top one. The FSM A750F section labels one as the "No. 1 outlet oil cooler tube" and the other as the "No. 1 inlet oil cooler tube", but the drawing shows them hovering in space above a view of the driver's side of the tranny when in fact they're on the passenger's side, so the drawing is somewhat ambiguous. Experience tells me to not waste my time asking Toyota. Can someone who knows for sure tell me which is the tranny outlet line (hot) and which is the tranny return line (cold)? The good news is that the Boss approved the purchase of an infrared temp sensor, just so we "could be really sure". I really want it to use on the trailer wheel bearings and brakes at rest stops to spot abnormal increases in temps, so this was a good excuse to help justify the purchase. Also for tracking the temp for ATF level checks. Also for documenting ATF temps before and after adding the cooler.
Any thoughts would be appreciated, so thanks in advance.
