FJ40 t-case troubles...

[mountain cruiser]

Anyone local have a ton of experience with FJ40 T-cases? I have spoken with Mikeob1 and done my fair share of searches over in the 40 section, and both agree from just a discussion that it's most likely that the idler shaft is bad. It was mated to a 700R4 with an Advance Adapters kit, and at that time the transmission was rebuilt and t-case was supposedly gone through....? I am looking for someone with a decent amount of personal experience with 40's in general that can go for a ride along before I go tearing into it.
Sucks that the only 2 things I outsourced on this build are giving me trouble. Thankfully though, the light is at the end of the tunnel.

Thanks in advance.

 

[inkpot]

Howdy! I have had a couple of them rebuilt, and the idler shaft always seems to be the single most common weak point. It is the same thing for both the 3 spped and 4 speed version. I don't know about the newer split case ones. Most common reason for wear/failure is low lube level. If the front seal in the transfer case fails, it pumps the oil into the transmission, so you never see a leak. Therefore they get run a lot without proper/any lube. Second reason is that the itty bitty needle bearings are not up to the stress of bigger tires and extra horsepower while they spin around that itty bitty idler shaft. Even with a fresh rebuild, the 3 speed box will be much noisier that the 4 speed one due to idler gear size/shape/angle. So what's yours doing wrong? John

 

[mountain cruiser]

Chatter on deceleration. Well, I will dive in and see, and hopefully it's that simple. I am crossing my fingers that its just the idler shaft and bearings.

 

[inkpot]

If you DON'T have a PTO drive gear on the transfer input shaft, you may be able to inspect the idler for runout by just removing the side inspection cover. I think there are supposed to be shims on either/both ends of the idler assembly, but I don't remember for sure. If it's too loose, it might chatter as the Reverse pressure moves the idler off of the "sweet spot" that it normally sits in while running in forward gears. Look for tapered teeth on the big idler gear, as this would indicate wear on the shaft itself. Keep us posted. John

 

[inkpot]

Oh, just remembered another goodie. I have seen the bearing spin in the bore on the rear of the case where it supports the input shaft. I had to shim it up to secure it. John

 

[Tools R Us]

Agree, idler shaft/bearing/shim are the main problems I have seen. This is likely why they went to the bigger shaft/bearing on the later split case?

 

[mountain cruiser]

From what i've read that is the reason they increased the shaft size on later cases and it would make sense since this is the most common problem.