1973 J4000 T18 After Rebuild, Will Not Shift While Running

[Kowpie]

Greetings all
Have been a little depressed after what happened during the restoration of my '73 J4000. Have been doing a body off restore for the last year and I am nearing the finish line. Just got the truck started this weekend, which was exciting, and putted around the driveway to check brakes, transfer case, and transmission. Sadly, I have an issue. Looking to see if anyone has heard of this situation before? Freshened up the T18 when I had it out, surfaced flywheel, new clutch disc, new pressure plate, new release bearing, new pilot bushing, new synchros, new snap rings, new ball and roller bearings, new cover shift rail springs and detents, and new seals and gaskets. Shafts, gears, and shift forks were in good condition. All parts were quality items from Novak. Now that it is installed and I finally have it running, the trans will shift into all gears while the engine is not running. Start it up and idling, I get a swishing or whirling sound while in neutral. Just barely take some pressure off with the clutch pedal and the swishing sound goes away. While idling, I can get it into what I call 1st gear (not the low or "crawl" gear) fairly easy but 2nd and 3rd are tough. Head down the road with any speed, and it will not shift gears. Not that they grind or even try to go in gear, it is like there is no slot to slide the shifter into. If you take it out of the gear you started out in on the highway, you have to stop before you can get it back into any gear. I have checked clutch adjustment and it is fully released. I have restored several manual and automatic transmissions over the years and this is my second T18 so I am not a total novice but I certainly am not a professional builder so I could have done something wrong. Before I drop this thing back out, which I am dreading, does anyone have any ideas? Thanks for your input. Since we all like pictures...

[Yeller]

Nice looking pieces!!!

My first gut instinct is the clutch is not releasing all the way. But if that was it you probably wouldn’t be able to shift it into reverse with the engine running. You might be able to get into a forward gear due to the synchronizer slowing the input shaft enough to allow it to go into gear. However if that was it you should still be able to float the throttle and shift gears without the clutch. I can’t think of anything that would cause this issue except maybe the preload on the input shaft being too tight making it stop turning when you press the clutch. I can’t remember off hand if that is even possible on a T18.

As for the whiring noise, my assumption is the clutch is adjusted a touch too tight, or the clutch return spring is not holding the throw out bearing away from the pressure plate fingers. What ever the cause from the description the throw out bearing is just touching the pressure plate fingers.

[Kowpie]

Thanks Yeller, high praise as you have created a wonderful rig.
I'll do some more fiddling with it tomorrow after work to see if I can check any of the items you mentioned. I used to drive an ancient concrete mixer truck so I am well versed in matching engine input shaft speed to road speeds and I tried all the tricks I knew. Nuthin! The release bearing fork was severely worn and I had to build it up and file down the tabs that find purchase in the release bearing collar grooves, maybe my machining skills are to blame? Another opinion was the pilot bushing was too tight, thoughts?

I appreciate your input.

Gary

[tgreese]

IME if you can start the truck without moving forward, the clutch is - at least - mostly releasing. Even if it did not release, you can drive without a clutch if you match speeds. These truck 4-speeds are heavy shifters and unless you are exactly matched, will take some strength to shift without the clutch release.

Pilot bushing is an interesting thought, but again you should be able to match speeds and shift.

If you have the clutch disk in backwards, the TO bearing can click click click against the cover arms, assuming you have that type of clutch cover.

Again IME you cannot do much from the top. And it shifts with the engine off, so I would not first suspect the forks etc. I presume you have put it in each gear, started and driven to see that it will run and drive in that gear.

Don't know specifically, but I would suspect you have the synchro hubs assembled wrong somehow. The blocking rings are always blocking when the main shaft is turning.

[Yeller]

Old mixers were always interesting to drive lol. I’ve had tight pilot bushings cause some issues but if you can get into reverse without excessive grinding while it is at idle I wouldn’t think that is the issue. I say reverse because it is un synchronized. Even then it should float shift. When trying to shift does it ever grind?

I find these types of issue’s interesting. When fairly simple drivetrains refuse to cooperate I’ve seen I lot of weird things cause problems. At one point on my history I was a drivetrain drivability tech so I’ve seen some weird stuff.

[tgreese]

I believe you could put it in low range and drive around in 3rd or 4th no problem. You could test each gear and see if it will come out or gear, and possibly go into gear. This is more of a test than trying to shift from 1st to 2nd or 2nd to 3rd as you would from a normal 2WD start. May not tell you anything, but it seems you should check each of the possible gear transistions.

[tgreese]

BTW your engine compartment is very tidy. Nice. No split-loom yet in '73, again IIRC. Black tape.

That's the right engine color for a '73 - my new '73 304 CJ-5 came through in that color. Kinda think the modern paints are deeper and glossier than what came with back then.Original paint never looked that good. Looks nice though - spray can or gun? No paint on the transmission or transfer case IIRC - did you use some kind of gray cast iron coat for this? Looks good.

[Kowpie]

Thanks for the replies. I really appreciate the tips. Sometimes I find I need to walk away for a bit and seek wisdom.
A few answers to your questions:
1) I have driven it in every gear, even slipped it in 3rd from a stop to get going.
2) Shift into reverse while idling, yes. No grinding, just the usual slight release of the clutch to align the gears then it drops in.
3) Never grinds, will not even begin to slide into gear.

You guys have provided a few items to test tonight. My list:
1) Remove the clutch release fork and see if I can visually check for release bearing interference.
2) Double check shifting into reverse at an idle.
3) Clutch cover is a diaphragm style, will try to inspect for interference through the release fork access.
4) If I get deep enough, pull the vinyl, shift boot, shift cane, pull the top cover, and inspect the internals for possible issues.
5) Verify function in each gear with TC in 4L, 4H, and 2H.

[Kowpie]

BTW your engine compartment is very tidy. Nice. No split-loom yet in '73, again IIRC. Black tape.

That's the right engine color for a '73 - my new '73 304 CJ-5 came through in that color. Kinda think the modern paints are deeper and glossier than what came with back then.Original paint never looked that good. Looks nice though - spray can or gun? No paint on the transmission or transfer case IIRC - did you use some kind of gray cast iron coat for this? Looks good.

Thanks Tim, as I said to Yeller, I believe you gents have seen a lot of vehicles so your positive remarks mean a lot.
Interesting on the split loom. I have found SO many items that seem to go with earlier and later series on this truck. It seems 1973 truly must have been a cross-over year. A lot of parts match earlier Kaiser stuff, while several items match the 1974 and later AMC J-series. Adam from Jeep Recyclers refuses to believe they put the later style of dash in the month/year of manufacture on this J4000. Even though every indication shows it to be original. The loom appears to be original as well, even factory tees, clamps, and straps at all of the OEM locations. Loom even on portions of the harness that go to options that are not used on this base model. Same loom is found in hard to reach areas and all the way back to the farthest right side tail light. I do find split loom listed in my factory parts list from 1962-1973:

Group 8 (2).jpg

I believe you are right on the shade of blue. I purchased some original valve covers for my CJ-7 when I restored it and they had some of the OEM blue left on them. As you stated, it appeared a tad lighter. The paint is a Seymour AMC Blue EN-66. Correct again, I used a cast iron color paint on the trans and TC. I have worked hard at trying to keep it original but also clean. Thanks for noticing. Now if I can get it to shift!

Gary

[tgreese]

Huh. I know my '73 CJ had black tape, the kind with no adhesive that's just a wrap. Not a good comparison, because a CJ from that year has a grommet in the firewall, with no fuse panel and no bulkhead connector. The '72 TSM shows the same style of wiring for all models as my CJ did, with tape and no bulkhead. The above cited parts book should show the more modern style harnesses for '73, if that's the transition year. I will look at my '74-80 book when I get home.

You mentioned the month of '72-73 - what was that? Realize that spring '73 is late in the '73 model year, and Jeep (Kaiser esp, but AMC too) would incorporate changes when they were ready, even in mid-year. At the time my impression was AMC's revision program starting in 1970 planned lots of changes for the whole line, which were ongoing.

Regarding your pointing to wire loom in the '62-73 book, pretty sure that's not the plastic split loom we are thinking of. From my parts department days, I recall the plastic loom was not sold separately, but as part of that harness section. You'd get the whole big floppy unit in a plastic bag, connectors and wire and all. Repairing a harness was not a thing for the line mechs/techs. Also, it's only for the 232-327 trucks, and that part number is of ancient vintage. A number starting with "A" is WWII or 1946 vintage. That's something else. A17445 does not show up in a search, so I would guess it's a Utility wagon/truck part that put to use on the later model.

Good luck with shifting.

[Stuka]

My T18a always made a bit of noise with the engine running while in idle. I believe its because the big main shaft is always spinning while in neutral. If the sound goes away with you depress the clutch, I think the clutch is working ok.

To me your issue doesn't sound like a clutch issue. Especially if you can shift into 1st without any grinding from a stop. And I mean the granny gear, which is first, Jeep didn't do the weird renames that GM did with the SM 465 where they called 1st L, and 2nd 1st.

To me it sounds like there is an issue in the trans itself. Perhaps synchro's aren't happy, or some spacing ordering of parts is off.

[Kowpie]

Thanks Stuka
I get what you are saying but this is definitely a noticeable sound. It was silent before the disassembly. Yes, 1st (granny, low, crawl) is accessible from a stop about half the time, the other half you have to feather the clutch a bit to align the gears then it drops in place. I will probably pull the tunnel access and remove the transmission cover tonight to attempt some diagnostics. I will report back on my trials and hopefully, the fix. I have a couple of different exploded T18 diagrams but some of the finer details are left out. Know of a high resolution diagram?

Gary

[tgreese]

I have the Tremec T-18 book, which may be useful.

T18book (438 x 600).jpg

30-40 pages? May be useful. You can find it on eBay for ca $20. Look for the bulletin number.

Hard to pick from this because I don't know what's relevant or useful to you. Here is a typical page -

T18synchros (438 x 600).jpg

[rocklaurence]

Im thinking that the synchros arent correct--and its seems to be universal to all gears. It shifts when not rolling/driving which leads me to believe the synchros

[Kowpie]

Thanks for the tips.
Tim- I have ordered the manual. Much appreciate the reference.

Rock- I have removed the transmission and transfer case. Pulled the top cover off and inspected the shaft assembly thoroughly referencing every manual, diagram, and guide that I have. Additionally, there are several decent step-by-step utoob videos demonstrating correct shaft assembly that I spent hours reviewing. I have found nothing that has been installed incorrectly. The assembly rotates freely, synchronizers are installed in the correct orientation, no signs of galling or undue wear, shifts easily by hand and using the shift cane, all gears are in serviceable condition and direction, and the shift rails, forks, and detents all function as required. Release bearing is in new condition with no improper wear with proper lubrication allowing free movement on the front bearing retainer, friction disc was placed in the correct direction with nominal spline lube, and the release fork and associated parts all in good condition.
A fellow mentioned previously about possible interference with the pilot bushing. The I.D. of the bushing matched the O.D. of the pilot on the input shaft with factory specified dimensions but, there is a polished circle in the bottom of the crank bore beyond the bushing. The problem with this is there is no corresponding wear on the pilot tip.

I am at a loss.

[tgreese]

Ya know, there are two front main bearings for the T-18, with different thicknesses. Did we go through this? You need the thin one. If you could somehow install the thick one, it would both push the pilot tip into the flywheel and remove end play from the main shaft.

I would also improvise a caliper and compare the stickout to the pocket depth from the same plane. This is something you can measure.

[Kowpie]

Ya know, there are two front main bearings for the T-18, with different thicknesses. Did we go through this? You need the thin one. If you could somehow install the thick one, it would both push the pilot tip into the flywheel and remove end play from the main shaft.

I would also improvise a caliper and compare the stickout to the pocket depth from the same plane. This is something you can measure.

Now wouldn't that be something...
I have all of the replaced components saved in my hoarders stash. I will be comparing thicknesses tonight after the wood-stove warms the shop and some spirits warm the innards along with the checks you mentioned. Cheers.

Gary

[Herk]

What are you using for oil? Years ago I made the mistake of filling an SM465 with synthetic gear oil. The synchros just wouldn't grip the gears. When you tried to shift into 2nd 3rd or 4th you really had to lean on the lever to get them to bite. Swapped it out for normal 80w90 the next day and all was back to normal (SM465's aren't exactly slick shifting no mater what). Not saying this is your issue, but food for thought.

Once moving, can you shift without the clutch by matching the revs? If so, the problem is likely in the clutch. If not, it's likely in the transmission.

[Kowpie]

Thanks for chiming in Herk. Yes, using only real dinosaurs, no synthetics here. No go on shifting matching revs. Used to drive a very old concrete mixer for years and only used the clutch when stopped or creeping around the job site chute pouring the mud. I tried all of my big, rig non-synchro shifting skills to no avail.

Gary

[Kowpie]

So that others might learn from my experience, I believe I found the problem. I have a shaft from a previous T-15 trans build that just so happens to be the exact size of the T-18 input shaft pilot tip. I thought I would use this to check the depth of the pilot bushing versus the depth of the pilot tip. When I slid the shaft into the pilot bushing it stopped after about a 1/4" of insertion. Odd, I thought. So I removed the bushing from the bore and that is when I noticed a considerable "step" in the bore near the bottom of the crankshaft. From the picture you can see that this step has been transferred to the bushing reducing the O.D. It seems this step was enough to crush the rear end of the bushing. The outer end I. D.had proper clearance, but when the transmission is installed and the shaft is fully seated, the bushing grips the input hard. With this, the input was not allowed to release for shifting. This still does not explain why when I tried to shift gears there was no grinding and I had no success at double-clutching. Waiting now on a new bushing and transmission gasket set to reassemble. I do not know if the step in the crankshaft bore is supposed to be there or is a result of the lack of full factory machining? Maybe newer bushings are longer than OEM? I will be sure to turn the new bushings O.D. down accordingly at the location, then check the clearance at full depth before assembly. I am going to think positively and report back on my success.

Thank you for all of your input.

Gary

20221124_131109.jpg