Engine/Transmission (1994 - 1998) Forward transmission Cooler Question

[mwilson]

After a small tussle Saturday afternoon I got all three transmission cooler lines replaced on the '97. Also removed the rubber lines from the forward cooler so as to check them over and clean out the recesses in the quick disconnect fittings that fill full of guck.



I noticed that the ends on the cooler itself looked scarred up but as I had not done it I figured all was well.



Got everything back together and started replacing fluid. After a few minutes I started rowing the transmission back and forth between Drive and Reverse to build some pressure.



Got back under the truck and ATF is running out of the ends at the cooler...



Great.



After a few minutes of blue air I decided the easiest way to get the cooler out is to yank the front bumper (which by the way is the way to go... ).



Get it out and some pinhead back along has driven a screwdriver into one tube and repaired it with some kind of monkey dung (which I disturbed apparently)...



It also appears to be cracked where the small jumper tube is welded in between the two ends.



My question is this,,,



Does that jumper tube need to be there???



Can the transmission oil pump overpower the cooler so the tube is there to allow some fluid to bypass????



Don't really want to buy a new cooler ($250. 00) if I can save this one. Not worrying about having the tube would make it far easier to repair.



Let me know what you think.



Thanks,

Mike.

 

[mwilson]

No takers??? That's all right, I can't find the answer anywhere either.



I think that I will try to make a Hayden cooler work in place of the overpriced OEM one.



That would be the same one that the Fuller transmissions use for oil cooling.



I don't think that my little 47RE will over power that style.



I don't need no stinkin' bypass tube... . :-laf



Will show pics if I can make it happen cleanly.



Mike.

 

[mwilson]

This is what I am going to try to use... .

 

[DRAG DIESEL]

My question is this,,,



Does that jumper tube need to be there???



Can the transmission oil pump overpower the cooler so the tube is there to allow some fluid to bypass????

Jumper: No, i believe that it is a bleed for cold weather to help get some heat in the fluid faster. Many makes of vehicles have a design similar to this.



Overpower: max pressure is about 120psi on stock transmission. and that only happens in 4th locked up with your foot in the carpet.

 

[mwilson]

Ok, thank you for that. Had never noticed the bypass on any transmission coolers before.



I have ordered a Hayden, we normally stock one but were out yesterday. It is offered thru Freightliner as an assembly already mounted to a slick bracket/shield.



I think that it will fit but if not I will trim the ends of the factory cooler back beyond the bypass tube damage, put a slight flare on them and hook it back up.



It is a 3 pass cooler with 1/2" tubes so the fluid will flow freely.



Mike.

 

[DRAG DIESEL]

typically you won't see it on the cooler, ie: ford puts it on the lines right next to the case. now it's internal I believe.

 

[cerberusiam]

Not sure where the bypass is on a 2nd gen, or if they even have one, but the 3rd gens have a thermostat right there above the cooler input line. When the thermostat is open the fluid bypassess the cooler in a single run around the tubes until the fluid warms to around 140 degrees.



ATF+4 works much better when it is kept above 140 degrees. Basically any trans fluid is going to perform better when it is warmed adequately. The aftermarket coolers are definitely cheaper and just as effective but lack the thermostat for quick warm up. If you have a jumper tube off the inlet its a good bet the thermostat is there.



In your area and driving it in the winter, warm the trans well before driving much and very hard if you use a different cooler. Cold weather is really hard on an auto to begin with and unless the fluid gets warmed enough before trying to engage the clutches you can end up with seal damage.

 

[DRAG DIESEL]

It is a 3 pass cooler with 1/2" tubes so the fluid will flow freely.

More than likely... :-laf