Transmission getting hot

[saltlick]

My 720 transmission gets hot sometimes, but not all the time, and there seems to be no pattern to it, except it when it DOES happen, it's usually after driving it on the highway at higher speeds. It's a 5 speed manual 4wd and the 4wd stick shift even gets hot because so much heat radiates up through the boot. I thought at first it might be the cat getting hot so I had a new one put on but it still does it once in a while. Any ideas? It does have a vibration and a driveline shop said it needed the driveline rebuilt where it attaches to the the transmission (or was it the transfer case?) because there is a little play in it, but another dirveline shop said that play was normal and that it didn't need rebuilt (although he balanced the driveshaft but nothing changed),  and said that these trucks are notorious for that kind of vibration due to the divorced transfer cases. U joints are good they said and it isn't the tires. Anyone ever had an issue like this? It is having carb issues and using a lot of gas. I'm having a Weber 32/36 put on it in a few weeks.

[datzenmike]

Realize that it will produce more heat out on the highway than in town and although it is hotter it may be totally normal.

 

There are few things you can do for a transmission from the outside but foremost is checking the oil level. Properly filled the oil cools the gears and bearings and is flung around transferring the heat to the transmission case which radiates it to the passing air. The fill bung is half way up the side. Remove it and you should easily be able to dip your finger into the gear oil. The transmission oil should be changed every 30K miles, so if you have never changed it and you don't know when it was changed last then assume it's over due. The drain bung is on the bottom of the transmission and it has a magnet on it to collect ferrous metal. A black paste is normal, metal chunks or pieces is not. Wipe clean so you can inspect it next time. It holds 2 liters of GL-4 (NOT GL-5) 80w90 gear oil. Run 2 foot of garden hose down from the engine compartment into the fill hole and put a dollar store kitchen funnel in the other end and pour the oil down hill. If it over flows... it's full. If you get 2 liters in... it's full.

[Charlie69]

My 86 2wd king cab shifter gets hot on long highway drives.  I live in the Phoenix area.  Check the gear oil in the transmission and rear end when you change your oil and lube it.