James Birdsong

I just got home to California from a trip to Sturgis S.D. towing my 37' fifth wheel. The trans would do fine while cruising, but would heat up quickly (above 220 degrees) while going thru stop and go traffic. I already have the deeper trans pan with cooling fins). I'm looking at an added cooler, "Derale 15800". Has anyone used this? Any installation tips or locations? Thanks in advance, Jim.

no_6_oh_no

Where are measuring temp?

Have you removed the drain back check ball and modified the VB to circulate better?

The aux coolers are exactly for the conditions you are seeing under heavy loads, but, you really need to mod the whole system and VB pressures for the best result. Depending on where you read temp it may or may not make a big difference though.

James Birdsong

I've been reading the temp thru the Banks/pda/ecm. I have not modified the VB or check ball. How would I go about doing that? Thanks, Jim.

no_6_oh_no

Ok, your reading pan temp and could be as much as 20 degrees off actual read by a gauge. The temps are not high for this trans in those conditions. The operating temp of ATF+4 is 140-240 degrees and as long as you not holding over 250 degrees for excessive length of time it only a watch condition not a worry one. If you do a lot of towing and frequently hit htose temps then changing the ATF every 20k is highly reccommended.

The stock VB does not allow fluid to charge the TC in park. To stop the drain back and make the TC ready to go as soon as th engine fires a drain back valve was inserted in the upper cooler line under the driver side battery. If you remove the fender liner you can see and access it.

The problem with the drain back which is a check ball is it blocks 50% of the flow even when open. Cooling the fluid is allow about flow and the check ball is a huge blockage and garbage trap which can further reduce flow. The second problem is the amount of pressure routed thru the cooler when the TC is not locked is extremly low, on the order of 10-15 psi at low rpms. The bulk of the fluid is routed back into the sump to charge the TC in fluid coupling so not as much cooling happens at low\slow speeds.

A good fix for these little things is a shift kit to get your line pressures up to hold clutches better and promote better flow thru the cooler at low\slow speeds\rpms. Depending on the shift kit it will either charge the TC in park or you can add a manual valve from Sonnax thta does the same thing. The shift kit used will dictate what needs done.

Once the shift kit is done the drain back check ball can be removed with no ill effects plus the positive side is you get more flow thru the cooler at all times. That should help some, but, the stock TC is so loose in fluid coupling that it generates tremendous heat just trying to move a load. Given that and stop-n-go and hot ambient temps you are going to see some temps up there around 220 at times. An aux cooler will help in times like that but the temp rise can still get ahead of the cooling because so much more fluid is routed internally in fluid coupling.

The next step would be replace the stock TC with a billet unit that has a lower stall and better efficiency. A tighter TC will work the fluid harder generating a bit more heat but you spend less time pushing the fluid and use less throttle to do it so your actual temps usually end up lower in the same conditions.

Couple of ideas and things to consider,

James Birdsong

thanks for the info NO 6. This truck has about 90,000 miles on it. In your opinion is this too late to add a new TC? I had thought about waiting and replacing it with a new trans at a later date.
Do you recomend a particular shift kit?

no_6_oh_no

As long as it is still shifting good, no its not too late to replace TC or even clutches. If your going to drop the trans to replace the TC I would highly suggest going ahead and pulling the clutch packs and front band to rebuild and upgrade them. The direct clutches and the front band take the biggest hits in wear especially towing.

Whne you do a shift kit and raise the line pressures the pump needs to be pulled at some point to replaces the reaction rings on the pump snout with better ones to handle the higher pressures. You don't have to do it immediately but at some point its a good upgrade.

If your pan looks clean and OD engagement is good, I would be hesitant to rebuild the whole thing unlss you have the money and want the absolute security. As much as possible anyways because a complete rebuild does not guarantee no break downs.

The weak areas are direct clutch pack, TC, and front band. Add a shift kit and upgrade those parts and you have to thrash the trans pretty hard to make it fail.

You have the choice of 2 decent kits and some like DTT will put together a package that does the same thing. Along with the increased line pressures you need to upgrade the accumulator, front servo, and band strut and anchor. All those pieces can be had for around $100.

Couple things to consider.

James Birdsong

Thanks for all the info! This gives me a lot of options.