B&M 70273 or 70266 aux cooler for stock D5 converter?

#1
re-coring the radiator so it may be a good time to consider adding an aux. trans cooler. keeping radiator cooler...

not interested in coolers using barbed fittings and hose clamps. plan to use -6an hose and fittings/adapters.

70273 (aka Long/TruCool L7B) => 11 x 5-3/4 x 1-1/2 rated 15K BTU

70266 (aka Long/TruCool M7B) => 11 x 8 x 1-1/2 rated 20.5K BTU

old B&M catalog cites small block - greater than 3200 # with 2400 rpm stall converter to use the 70273

mounting will be similar to GNX cooler using custom brackets attached to existing radiator support holes via u-nuts/speednuts.

searching old threads on this topic yielded a pic of a 70266 installed as I'm planning, but that was for a modified car.
B&M 70266 install.png
70266 cooler is the layout size I'm looking for...not much of the Pro-Lite 350 hose would be exposed and the 1/8" stock for the brackets lines up well with the radiator support existing mounting holes. similar sized coolers at 3/4" thick all use hose barbs and clamps - not what I'm looking for.

Performance wise, one day I will go thru the trans but have no reason to go to a higher stall converter. I could replace the factory prom with a TT street chip - I don't like the amount of timing in the factory chip with today's pump gas, even at 14 # boost. With TT (and corresponding mods), it'll run at 16-17 # boost

Is the 70266 cooler TOO MUCH cooling capacity for a stock converter? Thanks for your $0.02.
 

David Husek

Turbo Buick Performance
#2
Hayden 678 is a good choice for a stock converter inline with a factory cooler. It is easy to install also. It is not what you are looking for but my recommendation for others that may be looking.

I wouldn't use anything but factory steel lines for a 200-4R especially using a lock-up converter.
 
#3
Hi David, thanks for the input. In the few dozen or threads I searched yesterday, I had read a few where you discussed the Hayden 677 and the 678.

I have a new set of stainless lines from Classic. braided hose would only be from breaking the top line at the radiator via the brass union and re-directing to the aux cooler via a 180* fitting.
for completeness, pic here is the standard means of connection with that 180* fitting. transcooler lines @ radiator.JPG

a few years back, @trick86 made a really nice complete kit using the same inverted flare fittings on the hoses so there was none of the adapting from AN to inverted flare.
see it here: https://turbobuick.com/threads/brh-trans-cooler-kit-the-best-street-strip-kit-period.355975/

I was trying for a cleaner install by attempting to use a 90* male 1/8 NPT to -6AN hose end at the radiator instead of the factory configuration. making the aux cooler connections at the factory brass union using that 180* fitting gets a little cluttered bringing the line out and around the radiator only to make a connection to go back to the front. but this new fitting won't fit with the condensing unit bracket almost touching the factory brass fitting at the radiator. and I don't want to fabricate a new stainless bracket for the condenser.

I was considering making custom hard lines to the aux cooler as well. It would be a nice clean install. I'd need to start with soft copper as prototypes and then go to the good 5/16 stainless. doing double flares on stainless is best done via a hydraulic flaring tool - something not everyone has at home. but don't know if I want to spend an afternoon designing routing paths for these lines and making test pieces/templates.

Back to my question: 170F to 180F is the ideal trans fluid temp. My GN as factory stock (PROM, 180F T-Stat, ect) maintained and operated at 200F water temp during dyno pulls (with that 4' diameter shop fan blowing in front of the car). the radiator recore is 3-rows of 1/2" tubes vs. the factory 3-rows of 3/8" tubes. slightly larger tubes and a new, perfectly flowing radiator core may lower coolant temps and in turn lower trans fluid temp. The addition of the aux cooler will lower trans temp further. maybe i have to do more research unless some can share hard temperature data using the 70273 or 70266 cooler on a stock engine and stock lock-up converter. Adding a TT street chip will change the radiator fan control settings (on @ 166F) vs factory prom (low speed @ 208F; high speed @ 226F). trans fluid temp is normally about engine coolant temp but fluid from the lock-up converter can reach 350F after a hard pull.

maybe I'm overthinking this. I'll call B&M to ask if they can share any delta T and design parameters for these coolers.
 
#4
considering that most of us put these cars away for the winter months and are not driving them in sub-freezing or sub-zero outside air temps, overcooling trans fluid just can't happen during the fair weather driving seasons. We warm up the engine to normal operating temp before driving AND the cooler in the radiator will temper the trans fluid anyway.

It seems like personal preference at this point once a minimum size aux cooler is confirmed like Dave did above noting the Hayden 678 in-line with the factory cooler in the radiator is a good choice for stock lock-up converter. Next, pick the cooler design type you like: tube and fin, plate and fin or stacked plate.

Remember that B&M coolers are re-boxed TruCool units made by Long. The B&M markup is like 70% more than the TruCool units.
B&M 70266 = $110 while the same unit in a TruCool box part # M7B = $64

Hayden and Derale make nice units as well.
Learn about them all here: https://www.transmissionrepaircostguide.com/transmission-cooler/
http://www.trucool.com/products/tru-cool-lpd
http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/Transmission_Engine_Oil_Coolers.pdf

I like the stacked plate design units so I'll probably get a TruCool M7B - car is a street car and not raced at a track. Racers don't like stacked plate or plate and fin designs as the potential to have those plates clog up with wearing trans components from racing extremes. Whereas tube type coolers will just flow back to the pan letting magnets and filters catch the stuff that may clog plate-type coolers over a race season, before performance loss is noted or catastrophic failure occurs.
 
#6
Hi Jim, exactly my point. Can't over cool trans fluid during fair weather cruising above 32F OAT's. I don't know of anyone who would take their turbo buick out in -20F winter conditions.

If your truck only has an external cooler (or maybe it has a cooler in the radiator as well as the aux cooler), trucks and tow vehicles would certainly have a thermostatically controlled bypass for operating in the sub-zero winters you get in MN.
 

David Husek

Turbo Buick Performance
#7
Hi David, thanks for the input. In the few dozen or threads I searched yesterday, I had read a few where you discussed the Hayden 677 and the 678.

Back to my question: 170F to 180F is the ideal trans fluid temp. My GN as factory stock (PROM, 180F T-Stat, ect) maintained and operated at 200F water temp during dyno pulls (with that 4' diameter shop fan blowing in front of the car). the radiator recore is 3-rows of 1/2" tubes vs. the factory 3-rows of 3/8" tubes. slightly larger tubes and a new, perfectly flowing radiator core may lower coolant temps and in turn lower trans fluid temp. The addition of the aux cooler will lower trans temp further. maybe i have to do more research unless some can share hard temperature data using the 70273 or 70266 cooler on a stock engine and stock lock-up converter. Adding a TT street chip will change the radiator fan control settings (on @ 166F) vs factory prom (low speed @ 208F; high speed @ 226F). trans fluid temp is normally about engine coolant temp but fluid from the lock-up converter can reach 350F after a hard pull. maybe I'm overthinking this. I'll call B&M to ask if they can share any delta T and design parameters for these coolers.
Sorry for the delay, real busy in the shop. Always best to call. I would just use the 1678 cooler with a stocker. It is easy to install, cools for what you need, it is plate and fin design which is correct for the 200-4R lock-up circuit to function correctly. A tube and fin design is wrong for a 200-4R. The sump operating temps should be about 160F - 170F. Anything above these temps for extended times takes life off the trans. Extreme cold is also bad as oil gets too thick and cannot be expelled during clutch and band apply.