overdrive issues

garage gnome · Jan 27, 2010

Anyone here have experience with an overdrive unit?

Last summer I bought an overdrive from Herm Tilford.
I installed it in the M38 fairly easily. But when trying to engage it, it never would engage without some grinding noise. After about 250 miles on the jeep, one day it finally would not stay engaged. I removed it and after inspection found the teeth on a brass syncronizer ground plumb off.

I called Herm to tell him of the problem I had with it. He said send it back so he can inspect it. After a few weeks I called him back to check on it. At that time it was already in shipment back to me. He said in all the years he has been doing over drive units that he has never seen one like what happened to mine.

Well Ok, so the other day the weather was warm and I decided to reinstall the unit. All the while contemplating on what I was going to do if I still had the old problem.

So after a couple of hours I got it bolted back in place and took it down the road for test run. The grinding is still present.
So get it back in the shop, jack the rear tires off the floor. Start her up and put it in gear and try to engage the overdrive again. depress the clutch and slowly try to enge it. It won't engage. A loud clash of gear noise.

So what to do now. I figure it ain't gonna work in my vehicle and I'm gonna have to sell it.

After about an hour of thinking and looking I think maybe I found something that could be the problem.

The linkage from the stick shift to the plunger on the unit is hitting the side of the transmission preventing it from freely actuating the O.D. into gear. I didn't take a photo of it. Darn It!

The linkage is a piece of 1/4" X 3/4 X approx. 12" flat bar with an off set in it to get it around the right side of the tranny and into the shifter. What I call dog leg off set. So I take the piece of linkage, heat it up with the torch and flatten out the 45's on the shift stick end. Entending on re-bending it so to give it more space between the offset bend and the part of the tranny it was hitting. I had to lengthen the offset slightly about a 1/4".

Got it back in and it appeared to be fairly mangeable. With out the engine running yet I could move the stick shift in and out without the linkage coming in contact with the side of tranny.

So I get brave enough to try it for real this time, With the jeep still jacked up I get the engine running and in forward gear depress the clutch and move the O.D. stick forward and it goes right in without a sound. Smooth as can be. Walla! What a relief. Next I take it back on the road and get it up about 35mph, depress the clutch and move the O.D. shifter forward and it slips right it like it suppose too.

I guess if I hadn't of been a green horn to overdrives that I might have figured this out the first time I installed it. However it would go into overdrive but not without that slight grinding noise.
So I kept running like that until it gave out.

But this time I wasn't going to do that until I figured out what was causing the problem. So now hopefully I will have long running overdrive.

Herm is a great guy to deal with. He repaired the unit and shipped it back with no charge. I haven't relayed my findings to him yet. But I will.

Well maybe my experience will help someone here in the future if they go the O.D. route.
Click to expand...

from another site.

Posimoto · Jan 30, 2010

Good job on the troubleshooting. Often times it's something simple like this, just takes awhile to figure it out. X2 on Herm. He's great to work with.

turbo · Feb 3, 2010

So otherwise would you say the upgrade to OD was worth the expense? Cost versus benefit?
Thanks

garage gnome · Feb 4, 2010

I got a photo of the linkage in place.

Click to expand...

turbo said:

So otherwise would you say the upgrade to OD was worth the expense? Cost versus benefit?
Thanks
Click to expand...

i don't know. i probably would say yes. this didn't happen to me, like I said, it was from a different site. It was more of a PSA than anything.

Warloch · Feb 4, 2010

turbo said: ↑

So otherwise would you say the upgrade to OD was worth the expense? Cost versus benefit?
Thanks
Click to expand...

I am a firm believer - I have one for each of my riggs, either in it or on the shelf for it.

windyhill · Feb 4, 2010

Warloch said: ↑

I am a firm believer - I have one for each of my riggs, either in it or on the shelf for it.
Click to expand...

X2!
Well worth it for me.

duffer · Feb 4, 2010

3x. Makes a very much more useful vehicle, both on and off road. Anything with an 18 gets one!

Mike S · Feb 4, 2010

Warlock, Windy, Duffer---------

Thanks guys, you just cost me another big chunk of $$$

Seriously, this is something I have been debating for awhile. Good to have the input.

garage gnome · Feb 4, 2010

I would like to get one eventually. they cost lots of $$$$. Unless I can find a junker for $100 with one in it...

windyhill · Feb 4, 2010

willyscjmj said: ↑

I would like to get one eventually. they cost lots of $$$$. Unless I can find a junker for $100 with one in it...
Click to expand...

I just did for $200. :twisted:

Seriously they are around if your lucky and willing to buy a parts Jeep for one.

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