So the entry road to the Laguna SECA race track has a 16% grade and my trailer weighs just south of 10k pounds. No way to get enough speed to lock up the torque converter. So I'm stuck crawling in 1st. I had to run for a few hundred yards with the transmission temp gauge north of 280 degrees. Ouch. A high idle at the top of the hill brought the temp down quickly.

 

The fluid doesn't look or smell burnt. I think I'm going to have it flushed out anyway. What are the chances that I damaged my freshly rebuilt 48RE? Is it typical to see the trans temp get up around 220 before TC lockup? You know - on a hot day leaving stop lights and such. As soon as the TC locks up, I can literally see the needle move back to 180.

 

What do you guys do in these situations? Would a transmission cooler fan help?

Just a passing thought... When was the last time you wash all your coolers? I've been doing A/C repairs in the valley and had several people come to me saying that A/C was poor or weak. Checked everything and pressures is good but the cooler was plugged up with mud and bugs. I wonder if this is your problem as well. You going to want a high-pressure garden hose with a spray gun or remove all the coolers and radiator and clean all them outside the truck. Either way, if the coolers are pack with bugs performance will degrade. Just with my past trip back and forth to Boise at 100-110*F out I tend to power wash the coolers weekly by then after 1,100 miles roughly they are looking a bit buggy and nasty. I know this is not going to fix the slow towing up hill problem but it might just help.

Probably never lol

Here's the rundown...

 

A stock 47RE valve body is not capable of lockup until 2nd gear. The lockup valve in the lower VB is fed fluid by the intermediate apply circuit, therefore no fluid to achieve lockup until 2nd gear. A stock 47RE valve body WILL lockup (with an external switch) in 2nd gear in "D" range only. In MANUAL 2nd, a stock VB has lockup hydraulically locked out. Having said all that, locking the converter in 2nd gear in "D" range is not a good idea, because is has not hydraulically eliminated the possibility of a 2-3 shift like it has in manual 2nd, and a locked 2-3 shift is extremely hard on the gear train and input shaft!

 

A stock 48RE valve body is capable of locking (again, with an external switch) in any gear, in any gearshift position.

 

So what's a guy to do with a 47RE? The good news is, that they can be modified to act like a 48RE valve body (with respect to the lockup). Both mods are fairly simple to do, but unless they are done, it will act the same as stock. I build valve bodies a little kind of an a case-by-case basis, depending upon a customer's intended usage.

 

A gas valve body (46RE) is left stock (as far as lockup goes) because they don't have the benefit of a beefy, multi-disc converter clutch like a diesel does, that is going to hang on at both high power settings and, more significantly, in low throttle, low line pressure situations; ie. descending a hill, locked up, with a heavy load. Mike (@Mopar1973Man), this is why yours won't lock in manual 2nd, or first gear. It's to keep your converter alive and happy...

 

Diesel valve bodies are a different story. As anyone who has corresponded with me knows, I only run triple disc converters behind the Cummins. With that in mind, I add the capability to lock in manual 2nd to pretty much all diesel valve bodies, unless the customer expresses complete apathy for this feature. If they don't care, I'm good with leaving it alone. As far as first gear lockup, again, it's a fairly easy mod, but I take it with a bit of a cautious approach because it CAN BE a safety issue. If you forget to shut off your switch as you come to a stop, that big diesel is going to want to keep going...possibly into the Kia in front of you unless you catch yourself and correct it. With an unmodified 47RE, at least the converter will automatically disengage when you near a stop and the VB commands a 2-1 downshift. Matt (@Notlimah), I gave you both manual 2nd lock and first gear lock capability.

 

In response to XC2's scenario, given a healthy cooler system (which I would suspect if you're running normal temps in all other aspects) first gear lockup would be the solution I would recommend. Although, I would investigate where your sender is located. It wouldn't surprise me if it was located in the hot line out of the transmission somewhere. It would be strange to get the entire system that hot, that fast. But, I suppose it is possible, depending upon how far you had to run it that hard up against converter stall. If you had the ability to pull the truck down into manual first (to lockout the possibility of any upshifts) and engage the converter lock switch, I think it would work well for you.

See Jon, I listened! Hahah

53 minutes ago, Dynamic said:

A gas valve body (46RE) is left stock (as far as lockup goes) because they don't have the benefit of a beefy, multi-disc converter clutch like a diesel does, that is going to hang on at both high power settings and, more significantly, in low throttle, low line pressure situations; ie. descending a hill, locked up, with a heavy load. Mike (@Mopar1973Man), this is why yours won't lock in manual 2nd, or first gear. It's to keep your converter alive and happy...

 

 Why I like @Dynamic he does the right thing for the owner. I knew we opted out of the whole lock up thing on my 46RE. I kind of knew about 2nd lock up on the 47RE (bit fuzzy) but now I learned about 48RE and 1st and 2nd lock up. That's Neat! Thanks for your knowledge on the topic.

Edited July 5, 20177 yr by Mopar1973Man