Hey...It's me again. Got to looking at my rear end today...well..the trucks rear end!!! lol. Was trying to identify the kind that is there. I'm not sure if it is an original one for the truck or not. I know that it has been apart, because the cover was put back on with blue silicon, and not a real gasket. Anyways...I tried to clean it up a little, and found only two numbers on it. They are worn a little, so I'm not sure the exact reading. I think it reads... F189, or maybe FL89, or E189, or EL89. I also found in big letters...GM9. This is in a 1961 1/2 ton shortbed stepside. I went to http://www.americanclassic.com but I didn't find anything that helped me there. If anyone can be of help, please let me know. Thanks A Hammer and Duct Tape can fix anything. 61RodMobile
i cann't help with those numbers but you might be able to find some more numbers on the axle tubes. the numbers i found on mine were on the axle tubes if you look at the rearend from the rear. cowboy
Hey Guys....got some more numbers for ya'll. Don't know if they are going to help any. I managed to pull the rear end out from under the truck about 10min ago. As for axle tube numbers, I didn't see any at all. I pulled the cover off, and tried to find as many numbers as possible without taking the whole thing apart. If I did that, I would just start counting teeth. But as far as teeth go, I did count 42-43 teeth on the ring. Only counted once, and got 42, but I know that a 3.07 has 43....anyways. On the ring, I found the following numbers....998 or 866 depending on how you read it, A big M, A 02, and someone had written in a grease pen T182. There also was a NF too. Then on the differential, I found the number NF GM25. Hope that someone can tell me what this all means. FYI...the reason I wana know is because I can't be sure that this isn't the original rear end, and I was looking at changing to a high speed one. If I already have one, then I'll keep my money!!!
I can't tell you what kind of rear you have by those numbers, but I can off you this. The gear ratio is determined by the number of teeth on the ring gear, divided by the number of teeth on the pinion gear. Problem is, without taking it all aprt, it's a little tricky to count the teeth on the pinion. Take a good look at the ring gear again, and you should find a number sequence similiar to x-xx. This is the gear ratio. For example, if it is 9-37, then it is a 4.11 gear ratio. There is also a date stamped on the ring gear and a GM part number i.e. GM 3838365. Hopes this helps a bit.
You're in luck. I just got my 60-66 Chevy assembly manual in the mail, and it says that in 1961, is a C10 w/ 3.90 (exc. positrac) Great book to have, I got mine from ##### truck www.lmctruck.com. Costs $30 and has everything in it.
