Overdrive Problems

Went out 'wheeling on Sunday, and was having issues with my overdrive unit on my dana 18...Seems to stay in direct or overdrive just fine in any forward gear, all the way up to and including full throttle, but when I was giving it any kind of power in reverse, the overdrive unit would pop out of direct drive and it would sound like I dropped a driveline (big dull thunk noise, and obviously no more movement). Why the heck would the overdrive unit not stay in direct drive under power in reverse and 4 low? Lots of snow, so back and forth 1st, and reverse a lot, and it was getting VEEERYY annoying! Thanks for the help.

 

I'm a newb to these but isn't the OD just on the rear driveshaft, so you should onlly use in 2wd?

 

The Warn overdrive is an "all range" overdrive, good for 2wd & 4wd. You might be thinking of the Borg Warner OD, I think it's only good in 2wd.

 

Ohhh...

http://www.public.asu.edu/~grover/willys/od.html

 

It bolts in the pto opening of the dana 18:



http://www.public.asu.edu/~grover/willys/od.html

Herm has a good history of the Warn OD here:

http://www.hermtheoverdriveguy.com/id20.htm

 

yeah, it doesn't pop out when in overdrive, just in direct drive, figured it had something to do with the rotational direction of the teeth, but assumed it should have enough grabbing power to stay engaged in reverse, not like my 225 is overpowered for it I wouldn't think. I guess I do need to check my mounts again. Checked them two trips ago, I guess I'll see how much they loosen up after each trip. Also, I get a LOT of chatter in the front end (I think) when getting on the power too fast in reverse, so I back off and restart slower and smoother until I don't get it. I'm shackle reversed, does that matter? Also, I don't have that buffer bumper under the passenger side for the torque arm or whatever between the transfer case and the cross member, could this have anything to do with the chatter? Thanks.

 

THE most important bolt on a Jeep with a 18 or 20 tc is the torque mount on the side. Without it you eat motor mounts, tranny mounts, u-joints, and clutches due to "hop" caused by bad mounts. Also been known to break aluminum adapters with ease. Not the direct cause of the problems, but facilitates wear in all other parts in the drivetrain.

 

Cripes, okay, I'll have to get one of those bumpers that goes under the torque arm, then! Anyone know the best source to get the best quality one available so I can get one ordered?

 

www.jeepdoc.com has good customer service.

 

I guess I may not understand some of this thread, but if the overdrive unit pops out while powered in reverse, it would appear to me that there are two possible problems. 1) with no snubber, perhaps your od shifter linkage is binding enough on the tub or case to pop it out; or 2) the nut is loose on the bull gear and putting enough internal pressure on the od to cause this. Either way, you will likely destroy the od driving it like this.

 

I am betting its the detent spring worn out and it only pops out in reverse because of the cut of the bowl gear....

 

Novak Conversions is another source for the snubber.

 

There may be a number of causes to look into. When I installed my OD awhile back I had similar issues. In short the mesh of the OD gear and the t-case intermediate gear needs to be within tolerance. The installation instructions from Herm (I bought a new Saturn unit from him) include this procedure, measured with a dial indicator. There may be a minor install difference between the Warn and the Saturn unit. Call Herm he can tell you. He is very helpful.

I would assume the unit was on the jeep when you bought it?

 

I bought an OD from Herm and after a few dozen assemblies/disassemblies had to get a shim pack (and put in the whole pack!) to put behind the large gear in the D18 to keep it from popping out of direct drive under high load. I'm less than impressed with the tolerances of Herm's overdrives, but I'm hoping it ages in time to be a fine wine.

The D18 was rebuilt by Herm himself and the overdrive was installed by Herm, and after it didn't work right the first time, I took the overdrive, in person, back to Herm and he did rebuilt it with some slightly more worn-in components.

It still pops every once and a while, about 2 years later...