Riddle me this?

[jimharold]

I am doing the 727 to 46RH swap and all the info I find says to upgrade to 3/8" line. Well when I removed the trans from the donor truck it had 3/8" line but only 1/4"NPT fittings to the trans. And if you put a drill bit into the trans holes for the tubes they are only 9/32" (.281"). And 5/16" (.312") the old tube size for the 727. But the advice of 3/8" (.375") tube for the new 46RH has me wondering.

I'll be keeping a record of the parts needed for my swap and will post it on here also.

And is there any recommendations on oil coolers that work for this swap? Easy location in front of the radiator.
Jimharold

[PwrWgnDrvr]

The restriction to flow thru the smaller fitting is minuscule compared to the restriction of a smaller feed line. The longer the line, the worse it is.

Those brown hills look like CA!

[martincom]

You should still utilize the cooler loop in the bottom of the radiator. A tube submerged in a liquid can dissipate a lot of heat. If you want to supplement that with an air cooler, I'd utilize the largest I could mount.

[nutz]

yeah i would think they restrict it so it has time to cool the fluid
bigger is better,and run it threw the rad to control the temp.
and to help warm it on cold days

[sixpak340]

Larger diameter line;

Produces more fluid capacity.

More outer surface tube area equals extra heat dissipation.

The last time I added a transmission cooler for a truck, I ordered one for a school bus. I plumbed it into the loop after the radiator tank had done the 'pre-cooling'.

[712edf]

^^^^This. Routing through the cooler AFTER the radiator is sort of insurance against a faulty radiator adding heat, not that it ever happens.

Increasing fluid capacity, pertaining to antifreeze/oil/ATF reduces the strain on the system.

Bucky

[Conductorblg]

I've detailed my 47RH installation here before, but here is a recap on the cooler lines.

I used the 3/8" cooler lines from a a '90 pickup with a 518 and spent several hours carefully adjusting (slightly bending) them around the various obstructions (crossmember, power steering lines, brake lines, shift linkage, big block, etc.). It did require a 45* brass fitting at the transmission port to tip the forward cooling line up over the crossmember. With all the tight component clearances around the engine and transmission, rubber lined Adel clamps bolted to aluminum bar brackets (home built) hold the cooling lines in rigid alignment. The brackets are held off the oil pan by short sections of tubing and longer oil pan bolts. Because it's for the original 5/16" diameter lines, I bypassed the lower radiator tank cooler entirely, and used an external 11" X 11" X 1 1/2" stacked plate cooler mounted in front of the radiator. This cooler does the job of cooling the transmission perfectly using only the engine fan, even on 90+ degree days.

[swptln]

Bypassing the radiator for the tranny lines doesn't seem like a good idea on a OD transmission. Most of your OD's are designed to lock OD out at temps below 50 degrees engine temp, that's the major roll on the radiator, to help heat up the tranny fluid. All those era tranny's were controlled by the PCM via a engine temp sensor for OD. How much damage will it do? I don't know for sure, but it was done for a reason and I suspect it's because of the clutches, 800lb spring and feed lines in the OD unit for better flow or circulation. JMO

If you really want to increase the flow, use 1/2" tubing, that's what was used on all the Cummins 46 and 47RH's. It's a *#%^$ to find and get fitting for 1/2" tubing, but helps a lot on those tranny's. Just as an FYI, Dodge offered an auxillary transmission cooler for the Cummins equipped trucks from 89 on up that mounted under the bed front quarter, I have one on my 93 D250 and it works awesome, it has it's own fan and temp switch and runs automatically.