Hey Guys, I recently had a failure of my 4.7 gear driven case on the Rubicon trail on Cadillac Hill. I was able to luckily drive out using my 2.28 case and I was able to drive home in 2wd. A friend of mine with a lot of experience in the industry told me gear driven cases fail much more frequently than chain driven cases. I'm considering ditching my gear driven case set-up and going with a Northwest Fab dual case set-up. If I go that route, I have to switch to a R-Series transmission, and either get a full replacement bell housing or an adapter that will bolt to my 22RE engine. It will be a fairly costly modification compared to just rebuilding my 4.7 case.

I'd like to hear more opinions on the subject of the strength and reliability of gear driven cases vs chain driven cases. I'd really like to avoid a failure like I had in the future. I bought my 85 4runner already built. The transfer case always made noise under deceleration in 2wd, and I just assumed that was normal, but maybe it isn't. I'm now wondering if I was getting advanced warning that the transfer case had an issue or was what I was hearing is normal for these cases? At the end of day, the day before the case had the failure, there was clearly a difference in the sound of the transfer case that both I and my buddy that was riding with me could notice, but there wasn't really anything we could do about it at that point since we were deep into the trail at Rubicon Springs. I did check the gear oil level, and it was full.

So, please let me know your thoughts on this subject. Thanks!

 

You bought this rig already built so you do not know the quality of the parts used, or the care taken building it.
Or what kind of abuse it had already suffered, for that matter.
Please follow up and report on the exact nature of this failure.
As far as I know, there is no possibility of changing the stock reduction in chain drive cases.

 

You make valid points. You are correct that you can't change the gearing in chain drive cases. You're stuck with the gearing they have, which I think would be 2.56.

If I were to rebuild my 4.7 case, what gear set would you recommend? I know Marlin Crawler has their competition chromoly gear set, Trail Gear has a set and I think Sumo has a gear set as well.

 

I am running two different cases I built myself that use Trail Gear gearsets. I have had no problems with them.
I am also running a Trail Gear adaptor to join a gear drive case to an R series tranny.
I built a couple more cases for other people that are still in service as well.
I bought those gears because they had a good price point at that time.
In the years since then, it appears to me that Marlin has made several different innovative improvements in oiling and strength of their gears.
That would likely make me favor their product if I was buying 4.7 gears today.

 

Sounds like it was already eating itself when you got it. They are pretty tough if built properly with quality parts and kept filled with oil. What brand adapter and gears? I just have an AA T2X dual adapter and TG 4.7 gears behind a 3.4 V6. Running 35's and 5.29 gears without trouble for well over 10 years.

I'd find out what caused it and I'd probably stick with another gear driven case. It's not like you're running big V8 power. Advance adapters has a thicker casting gear housing that's already clearanced for the 4.7 gears and they are often on sale. Build it with good Nachi or Koyo, etc. bearings and quality gears and it should serve you well.

Let us know what you find and decide to do. Dead end threads suck. Good luck with it.

 

I'll definitely let you guys know what failed when I get the case apart. Thank you for the opinions and information so far.

 

I broke a 4.7 tg gear set a few years back. Not a cheap break, and ive heard it happening to a few people.




I replaced with SUMO gears, they are supposed to be be better. Its been 4 years now and still good. (the Tg gears made it 6 years)

Link to my build thread with more pics: https://www.yotatech.com/forums/f199...l#post52449630