I know I will get a lot of reads with that title. Hopefully, I will also get an answer. Does anyone know, or how can I determine whether the rear (axle, differential, etc.) of a 1989 and 1990 Chevrolet Suburban are either identical or compatible. The dealers I have contacted have not been able to help, and an internet search was not definative. Needless to say, I am going to do the work myself and really need to know before I get started.
There are usually several options offered in each model year, so for a definitive answer you need the letters and numbers from the ID tag on each unit. These tags are usually on one of the bolts on the differential housing cover. Possibly the option code would work – this can be found on a list somewhere on the vehicle, perhaps insided the glovebox door. A dealership parts department should be able to tell you where the option code list is located.
Salvage yards use interchange books that specifically address compatibility of parts across years and models. If you’re buying a unit from a salvage yard, they should be able to answer all of your questions. Otherwise, if you can’t find interchange info in a library or on the net, all I can think of is to call or visit a salvage yard and ask them to help you.
You’ll most likely have to crawl under it with a flashlight and wire brush (axles get dirty sometimes) and find the ID tag, then take the numbers from it and look it up in a parts manual. Hopefully the numbers will be the same on both axles.
They’ll probably bolt to the other-year truck, especially if the body style is the same (I don’t know when they made major changes on Suburbans), but the thing you have to worry about if it’s 4-wheel-drive is getting the gear ratio the same – you don’t want the front and rear turning at different speeds.
Go to this site and determine what rear end you have and the donor are the same. Both are most likely 8.875 inch 12 bolt rear ends. There were no changes in driveline choices between 1989 and the 1990 model years so everything should be an exact fit. The only difference may be the gear ratio. I did a lot of rear end swapping in my racing days including putting Ford rear ends in Chevys.