Here is the problem, When I got into my truck the other day started it and put it in gear, it did not move for a second before gently going into gear. Being a transmission rebuilder for over 30 years, my experience told me I had a problem. My best guess was that the transmission was low on fluid, so I went ahead and checked the transmission fluid. Sure enough it was almost 2 quarts low. Well that is enough to cause a mild slip on take off.
I knew what the problem was because it’s my truck and I drive it everyday and when I did a swap over from a T-400 transmission to to a Chevy T-700R4 overdrive transmission my lead rebuilder inspected the transfer case and told me the bearings were good. I guess my brain was not functioning right at the time. It seemed odd he didn’t just put a bearing kit in it. I’d sell you one if it was your truck.
I pulled the truck up and checked the fluid in the transfer case, and low and behold it was about 2 quarts over full. I’ve seen this many times on four wheel drive vehicle where the transmission and transfer case bolt together. The part of the transfer case (seal retainer) that bolts to the back of the transmission has two seals in it, they go back to back so the transmission fluid stays in the transmission, and the transfer case lubricant stays in the transfer case.
Simply put, one or both of the “retainer seals” are leaking transmission fluid into the transfer case, causing it to run the transmission low on fluid every 2 or 3 months and then it starts to slip on take off, cold. Cold is important to mention because transmission fluid expand like crazy when it gets hot, so in the early stages of leakage, the slippage goes away as soon as the transmission fluid gets hot.
It’s a great way to end up needing a rebuilt transmission, by not attending to a leak such as this and just draining the fluid TC and refilling the transmission fluid. Like I am doing now. So, do what I say and not what I do, in this case.
The bottom line is once the diagnosis is confirmed it’s time to get it fixed, or you will be shopping for a replacement transmission or transfer case soon.
[...] The cure to the leak problem is simple and right to the point. I would start by draining the transmission fluid out of the transmission and the lube out of the Transfer case, Then I would remove the transfer case in a careful and methodical manner to see why the transfer case seal was leaking. [...]