Herms 30% OD unit I'm at my wits end.
- Thread starter CHUGALUG
- Start date
OK I pulled everything out and put the OD in direct drive. And then reassembled the two halves and with the Brass Blocking ring fully seated on the dogs. The Syncro collar gear can not come close to fully seating with I estimate over .100" of the Teeth on the Planetary side still outside of the collar. If I then remove the Blocking ring the locking collar will cover almost .090" to .100" more of the gear on the Planetary. SO something just ain't right.
I am thinking if the wife is feeling well enough to be left alone for a few hours of driving up to Herms to see how to remedy this. 15,000 miles I have been fighting this thing. It was rebuilt once by Herms son Adam who is quite sharp on these. But it still behaved the same way. I added shims and got to the point it would not even suck up to the transfercase.
This is how the teeth look the thin curved line is the edge of the syncro collar. You can see how far the teeth are still sticking out.
I am thinking if the wife is feeling well enough to be left alone for a few hours of driving up to Herms to see how to remedy this. 15,000 miles I have been fighting this thing. It was rebuilt once by Herms son Adam who is quite sharp on these. But it still behaved the same way. I added shims and got to the point it would not even suck up to the transfercase.
This is how the teeth look the thin curved line is the edge of the syncro collar. You can see how far the teeth are still sticking out.
A SOLUTION
| OK I know I got a bunch of threads on this spread around the forums. I drove up to Herm's this morning. I had an appointment with Adam his son to finally figure out WHY this thing (my 30% ATV OD) has never worked correctly) A little less then a 2 hour drive. Adam tore right into the thing and in short order determined the Shift rail was the problem. In a nut shell the detente notch for the direct drive position is in the wrong place. This results in the Syncro collar not moving forward enough to completely engage the Gear on the Planetary. He said he had just learned of this being a problem on a unit he worked on just a couple weeks ago. When working on one unit you would never notice that was a problem because there is nothing to compare to. He happened to work on 4) units at one time for a customer and when he put the four shift rails on a pin through the shift fork holes he noticed one of them the notch was not in the same place (this unit had been having the same problem staying in gear). So investigated more and sure enough that was causing the problem. So once he knew where the problem could be coming from he then figured out where and how to measure the Collar in both Direct and Over to be able to tell if the notch was in the proper place. SO a New Shift rail and fork corrected the position problem. While he was in it already I had him go ahead and replace a couple parts that showed some wear after the 10,000+ miles since the last time he had it in hand in Aug of 2024. New Blocking rings and a Triple check of the collars position in Direct and $100.00 and I was headed home 2.5 hours later with basically a rebuilt OD unit that should now work as designed. He said he was surprised at how little wear there was on most of the Unit which we agreed was due to my obsession with the oil level. I'll get it installed some time this week (a number of Doctors appointments to deal with) And report on the results. So no amount of shimming would have ever made it better. He said to run the same amount of shims I had in it and all should be good LOL. Now to crawl under CHUG a half dozen more times and get it installed. |
I was charged nothing for the New Fork the New Shift rail or the labor the $100.00 covered the two new blocking rings and a couple other parts he swapped to basically rebuild it. I was tickled with the $100.00 cost. And this is on top of the last rebuild which he did in Aug 2024 that cost me only shipping. Because they wanted to try to find out why it would not stay in Direct at the time. As I said the problem found was one no one had seen before.
Chug,
You and I know of each other from different websites with different screen names.
I'm certainly NOT an overdrive expert, but I do sometimes hoard jeep components I think are worth it.
Overdrives are things I seldom pass up.
You confirmed in a past post that the biggest difference between the 25% and 30% overdrives was the outer case of the 30% being (.2 inches?) longer than the 25% unit.
This make leads me to believe that rather than an out of spec shift shaft, your 30% overdrive was built with the shaft from a 25% unit.
I'll eventually find the time to confirm the difference and whether it supports this theory.
For those of you that have a WARN unit from the 1960's, have you noticed that the T90 synchros that were use had circular "spots" milled into the synchro, and a brass set screw to hold the synchro in place during assembly? I have one if a 1953 CJ3B that I use on the beach, 40,000 miles of use. I've pulled the overdrive a few times for service like replacing the clutch.
I had an instance last summer where the overdrive "jammed up" and wouldn't shift.
Upon close inspection I believe what happened was that the brass screws backed out of the hub and jammed things up.
If you've got a unit with these, I would just remove the brass screws and use brease to hold the syncros in place during assembly.
Yes, I have photos, but it may take me a while to post them.
Congratulations on getting it fixed.
You and I know of each other from different websites with different screen names.
I'm certainly NOT an overdrive expert, but I do sometimes hoard jeep components I think are worth it.
Overdrives are things I seldom pass up.
You confirmed in a past post that the biggest difference between the 25% and 30% overdrives was the outer case of the 30% being (.2 inches?) longer than the 25% unit.
This make leads me to believe that rather than an out of spec shift shaft, your 30% overdrive was built with the shaft from a 25% unit.
I'll eventually find the time to confirm the difference and whether it supports this theory.
For those of you that have a WARN unit from the 1960's, have you noticed that the T90 synchros that were use had circular "spots" milled into the synchro, and a brass set screw to hold the synchro in place during assembly? I have one if a 1953 CJ3B that I use on the beach, 40,000 miles of use. I've pulled the overdrive a few times for service like replacing the clutch.
I had an instance last summer where the overdrive "jammed up" and wouldn't shift.
Upon close inspection I believe what happened was that the brass screws backed out of the hub and jammed things up.
If you've got a unit with these, I would just remove the brass screws and use brease to hold the syncros in place during assembly.
Yes, I have photos, but it may take me a while to post them.
Congratulations on getting it fixed.
That's interesting. It could be a case of the Shift rail being from a 25% but Adam seamed surprised at the distance between the two notches. And referred to it as a manufacturing error if I am not mistaken.
In any case its all back in and waiting until I can get some gear oil in to take it off the Ramps and out for a test drive. I have a great place 14 Blocks from my house to test anything to do with popping out of gear be it tranny transfer case or overdrive. Silverton has a 2 block long section of Main St. that is a 12% grade. Though if this has corrected the problem I will know before I get there.
It looks like I might have to do a little bending on the Overdrive shift lever the additional travel of the Shift rail looks to be causing the Shift knob to hit my console when shifting. A simple bend in the cane will fix that.
In any case its all back in and waiting until I can get some gear oil in to take it off the Ramps and out for a test drive. I have a great place 14 Blocks from my house to test anything to do with popping out of gear be it tranny transfer case or overdrive. Silverton has a 2 block long section of Main St. that is a 12% grade. Though if this has corrected the problem I will know before I get there.
It looks like I might have to do a little bending on the Overdrive shift lever the additional travel of the Shift rail looks to be causing the Shift knob to hit my console when shifting. A simple bend in the cane will fix that.
Well I finally had time to get CHUG down off the ramps and to run it around the block and it would appear the OD no longer pops out of Direct. In first gear Direct I can even bounce the throttle and it remains solidly in Direct with no indication of popping out.
I have the trans cover (the one on the floor) removed and a couple of times I heard something that sounds almost like something touching a drive flange or the rear drive shaft. So I'll crawl under one more time and see if I can figure that out.
It is noticeably harder to shift out of Direct not sure if that is just because I am so used to it not really being in Direct or if its due to the increase in Detente spring pressure. I don't know if Adam left in my spacer or not. Either way in a couple hundred miles I am sure my muscle memory will conform.
Now to reassemble the Floor cover and get the controls attached to the trans shift cane put back in place. Then a longer test drive most likely ending up at the local car wash for a long over due wash. CHUG has been filthy since we got home from the RUN OF THE HILLS in Ashland in June. I hope I can get it clean again LOL.
I'm happy its finally working as it should be.
I have the trans cover (the one on the floor) removed and a couple of times I heard something that sounds almost like something touching a drive flange or the rear drive shaft. So I'll crawl under one more time and see if I can figure that out.
It is noticeably harder to shift out of Direct not sure if that is just because I am so used to it not really being in Direct or if its due to the increase in Detente spring pressure. I don't know if Adam left in my spacer or not. Either way in a couple hundred miles I am sure my muscle memory will conform.
Now to reassemble the Floor cover and get the controls attached to the trans shift cane put back in place. Then a longer test drive most likely ending up at the local car wash for a long over due wash. CHUG has been filthy since we got home from the RUN OF THE HILLS in Ashland in June. I hope I can get it clean again LOL.
I'm happy its finally working as it should be.