I deliver mail with my 1979 jeep cj7. I have had a problem with it overheating on me. First we thought is was the radiator so we replaced the thermostat and then the water pump. That didn't solve anything. Now my husband thinks it may be the transmission overheating. What are some things we can check to determine if it is or not?

Most likely, the radiator needs replacing, due to corrosion or phosphate scale clogging internal passages:

http://www.autozone.com/autozone/catalog/parts/partsShelf.jsp?categoryDisplayName=Climate+Control&fromType=parts&fromString=search&parentId=cat30062&currentPage=1&filterByKeyWord=radiator&isSearchByPartNumber=false&navValue=15200172&categoryNValue=15299999&fromWhere=&itemId=prod61690&displayName=Radiator&searchText=radiator

A good way to find clogs is to use an infrared thermometer to "scan" the surface of the radiator for cold spots. If clogged, the radiator should be removed for cleaning or be replaced.

In the future, only use a 50/50 mixture of the recommended antifreeze and distilled water. The link below should help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post235973

Switching to full-synthetic engine oil and full-synthetic automatic transmission fluid (e.g. Mobil 1) will definitely help. Synthetic ATF will likely drop the transmission's temperature, which cools via the radiator, by up to 50 degrees F.