727 Transmission cooling

[Wietse]

Hey all,

At the moment my car has an additional cooler for the transmission oil.
This flows from transmission, trough the bottom of the radiator, exits from the other side and continues trough a hose to the extra cooler sitting in front of the radiator and after returns to the transmission.
Currently this setup has too many connections etc. that are a potential for a leak or burst and i am looking to do a reliable upgrade. (i changes from brass tubing to hose with hose clamps etc.)
My idea is to get braided hose (some say fiber, some say stainless steel) with fittings to bolt directly on the transmission and cooler.
While hooking up i will bypass the engine radiator and use a dedicated radiator only that will be installed in the same place is i have now.

My question is, what type of fittings (name/size) are needed to go on the transmission, and i need similar adapters to fit onto the cooler.
My guess is i need AN -4 but rather have someone confirm this.
And what is best to go for hose wise? fiber or (stainless) steel?
Would it be advisable to install an in-line filter as well somewhere?

Hoping on some good suggestions!

 

[493 Mike]

Keep in mind that cooler line pressure maxes out at 30-40 PSI so braided stainless plumbing is overkill. The flow leaves the transmission from the front fitting (1/8" NPT ) and returns through the rear fitting ( 1/8" NPT ) and should be directed through the axillary cooler first, then through the radiator cooler. This allows faster fluid warmup and removes some of the heat load from the radiator. OEM tubing is 5/16" on older Mopars so size accordingly. I would use as much steel tubing as possible and stay with flared fittings like OEM. The factory system has worked for decades so you shouldn't have to reinvent the wheel!
Mike

 

[wyrmrider]

Hi
just use half inch oil proof hose Pressure will drop to under 30 lbs if going through the radiator and to less than 15 lbs if using only a cooler with half inch in and out (100plate cooler) Many ford trucks have larger coolers
if you "build" your trans then drill and tap for larger fittings and open up the internal oil passages
If you are in cold weather area then go through the external cooler first then through radiator
in moderate temp or high temp area just use external cooler the radiator cooler is very restrictive
use ATF+4 - it takes the heat and cold better than earlier dino oils (well it's a dino oil that has been syntheticised to type III)

are you road racing ? if so I'd use redline ATF group IV-V synthetic

 

[Wietse]

I am not doing any racing or whatsoever with the car, going road trips and car shows and pull a race at the traffic lights is my plan.
As the car currently has this additional cooler i assume it was installed for a reason.
Keeping in mind the engine has been modified and produces some more hp then normal (no facts on paper) and the car currently has a 4.10 lsd type rear axle.
Then again, ambient temperatures here would be 25 Deg c in summer, down to -5 Deg C in the winter at most. (winter i will most likely not drive anyway)
If the extra cooler i have now is absolutely no use for these conditions i might be better off removing it and install OEM style tubing?
How hot would the oil get and what is acceptable?

I already have purchased Kroon AFT Dexron II-D oil to replace whatever is in there and install a new suction screen, so while i am at it i could sort out the cooling system as well in the meantime.

https://www.kroon-oil.com/en/catalogue/product/64/atf-dexron-ii-d/26/

 

[wyrmrider]

Hi Wietse
GM has not certified/ licensed Dexron III for years much less dexron II- it is unregulated The last DEX III was H I did not know anyone made Dex IID anymore
They just do not hold up in heavy duty use- which is not you
should work fine
and your current cooling should work fine
the Automatic transmission Service Group (ATSG) manual says the factory does not want more than half throttle for more than 20 seconds without a shift down to combat converter heat. You get the most heat "lugging" during towing or up hills or in stop and go traffic jams
Personally I would sell the Dex II and use a more modern fluid like +4
Just because even older manuals said to use Type A I would not use whale oil either
Thanks for the link- if they do not make it you do not need it They recommend SP 4026 for MOPAR (not Chrysler certified but should work)
I do disagree with the 20-50 recommendation for oil
but the Helar 0W-40 looks great
I checked a Jetta TDI and it recommends
Helar SP LL-03 5W-30 and that ones shows the correct VW 507 approval wrong oil here can ruin the expensive particle filter
They do not list an oil for Allison TES 295- shows some responsibility as opposed to say AMSOIL
The absolute best ATF right now is CITGO Quatrosyn- but you do not need it for a 727

 

[Wietse]

Thx for that info.
Personally i have absolutely no idea about the differenced in transmission oil, dexron II, III, B, D or H.
I just went as per recommendations on Kroon their website, here in the Netherlands we are kinda stuck as we do not have the insane variety you will see in the US with lubricants for Mopars and other US made cars from the good ol days.
For the engine i am using Kendal Racing Green 20W50, which was in there when i bought it and the mechanic from the shop recommended me to continue using it as it is a better oil for "race" engines.
I am not having any issues with the engine or unusual noise or rattles so i rather stick to it then trowing in different oils again.

Regarding the cooling, you think i am better of with reinstating the OEM system and be done with it right?
Only thing i wondered is to drill out the NPT/JIC adapters that are installed on the transmission and radiator to increase the flow slightly, even buying new ones and see what can be done there, they will be the bottle neck due to the reduced I.D.

 

[Ski 61701]

Do you know the stall speed of your torque converter? I would keep the aftermarket trans cooler hooked up, especially if you plan on towing. I feel for our European brothers and sisters trying to get repair parts and having to pay VAT and shipping.
Do you have a tube and fin cooler now or a plate style cooler? You might want to look at B&M plate cooler 70268 or a Derale plate cooler.
I run mine after it goes into the radiator on the output of rad I get a piece of 5/16 steel line and bend it so it goes right under the core support and bend it up to meet the cooler. I then flare it to put a barbed fitting on and just a short piece of oil resistant hose. The hose should take up some of the vibrations so you dont crack fittings on cooler.
Its what I do and it works for me, I get a 30 degree drop in temp from input to ouput of cooler before it goes back into trans. I check with infared temp gun.

Yes try and go with atf 4 if you can, but if your car currently is using what you mentioned you want to use , not sure if upgrading oil won't cause probs with friction discs in trans if they have been exposed to dextron II for all these years.
I remember using dextron II back in the day and not having probs with it.

 

[wyrmrider]

there is a reason that momma mopar went to 3/8 then 1/2 inch cooler lines
what wears on a torqueflyte?
the additive is +4 is for converter shudder but it also helps on the clutches
however the killer problem is the thrust washers
more so on an OD but still a problem where failure is fatal
the newer oils just do a better job lubricating the thrust washers and more cooler flow helps both to keep them lubed and cooled
mom mopar says to overfill the trans by a quart then put return line into a bottle you should get more than one quart flow in 20 seconds
any less replace the cooler in the radiator
adjust your level to remove any leftovers from the added quart

 

[Wietse]

I will not be doing any towing at all.
Other thing is the Netherlands are as flat as a pancake so no hill climbing or whatsoever.
Stall speed of the converter is unknown, the engine and transmission have been rebuild by a previous owner and i have no info on the internals.
The cooler is a 14"x10" tube and fin cooler, mine is lined up same as yours radiator first and after to the cooler.
I have not checked any temperatures as yet but never had any issues as far as i am aware, the transmission shifts ok.

Regarding the transmission oil, i have no idea what is in there at the moment.
For that reason i rather change all fluids so i know what is inside.

I just found a website that sells Mopar ATF +4 oil, maybe that is the way to go?

http://americanvehicleparts.nl/motorolie/

I guess it might be worth the to look for removing the bottle necks from the oil lines to improve the oil flow through the cooling lines if they upped the sizes themselves already back then.

 

[wyrmrider]

shop around
if it has Chrysler approval ATF+4 is ATF +4 all the same

 

[Ski 61701]

I would find a temperature gun and see what your temp difference is you might not have to do much other than upgrade the fluid to atf4. Just make sure existing trans lines are not kinked or bent excessively. If you can find out stall speed of convertor, that would be beneficial. If you have say a 3500rpm stall in the car, and you do a lot of highway driving at say 3000rpms you are not locking convertor up and its slipping which in turn creates heat. Id drive it on a road that allows you to reach highway speeds, drive for awhile and pull over and take the temperature of the cooler see what you get. You may want to convert to a bigger more efficient plate style trans cooler if the temp difference from inlet to outlet is minimal.
If you go to either Derale or B&M websites they explain things really well. Just trying to help possibly save you some money.

 

[wyrmrider]

Don't know about EURO availability but here is a picture of the cooler I usually use
http://vwcatalog.empius.com/vwcatalog/2016/48.html here the 9267
These coolers are made by several vendors- Mine seem to be from BORG WARNER CANADA
however I get mine from FORDS in the wrecking yards, oil coolers too
I have not looked at Derale lately and IDK who sources B&M they certainly do not make them

 

[Ski 61701]

Don't know about EURO availability but here is a picture of the cooler I usually use
http://vwcatalog.empius.com/vwcatalog/2016/48.html here the 9267
These coolers are made by several vendors- Mine seem to be from BORG WARNER CANADA
however I get mine from FORDS in the wrecking yards, oil coolers too
I have not looked at Derale lately and IDK who sources B&M they certainly do not make them

Thanks for sharing, those are some nice coolers. I use Derale because they are still made in USA. B&M shifted a fair amount of their stuff south of the border.

 

[HEMI-ITIS]

I would just use the external cooler and no fluid in the radiator.That is all I do,on pump gas I am driving with over 700 hp.

 

[wyrmrider]

Tube and Fin watch your temps do you have a IR probe? thanks for the pics Hemi

OP
you can also run an ATF that meets Allison TES389 about the ONLY approval for DEX III class fluids, GM has NOT licensed DEX III since 2005
(so your mileage may vary- quality certainly does)
Allison TES 295 is a better fluid and you do not need it unless really cold, really hot, or really long service life
+4 is a great fluid
Citgo Quatrasyn is the best (well maybe redline)

 

[Wietse]

Thx for the info guys!
Once the car is up and drivable again i will check the temperature difference with my IR gun and see what it does.
I don't think there will be a heat issues with the current setup given the ambient temperatures here and is i will not be racing or towing.
By continue to use the radiator section i think it will help warm up the ATF at first or not?
If that has no benefit i can just use the extra cooler instead as HEMI-ITIS says.

Going back to the cooler lines, if i would stick with the OEM style tubing i need to modify it again to plumb in the extra cooler.
Going with braided fiber hose and fittings i could make my own and avoid unnecessary connections and modifications to reduce the potential of a leak compared to what i have now.
If i am not mistaken, the adapters in the transmission are 1/8" NPT to 1/4" JIC (AN -4) right?
So with 1/4" ID hose i should be good. (comparing the 5/16" tubing is OD so ID would be similiar)
Opting for a 3/8" hose, the fittings will always be the bottleneck for flow, but assuming they could be drilled out slightly to increase flow a bit.

 

[wyrmrider]

little short bottlenecks do not make nearly the difference as long tubes
you do not need braided- just black oil proof hose
we tested for chrysler and half inch makes a big difference- also easy to calculate bends relationship to length- tight bends are a killer
just route away from the exhaust

http://www.allisontransmission.com/parts-service/approved-fluids/on-highway-fluids any of these available at reasonable prices or REDLINE atf