Transmission jammed in reverse

mitherial

mitherial

Well-known member
The transmission in my 1989 Turbo Diesel 90 (19J engine / LT77 transmission with E-suffix) is jammed in reverse ? which occurred within 30 miles of getting the clutch and flywheel replaced. The shift-lever now moves freely (to the point where I hit my hand against the bulkhead) but is completely disconnected from the transmission. Truck will drive backwards.

  • (1) I assume the most likely cause is a broken linkage, but is there any way to tell if it is an issue with the internal gearing without disassembly? Given the timing, I?d suspect a possible clutch mis-installation of some kind, but shifting was working as well as it ever has until it locked up at the gas station. Previously, truck was occasionally very difficult to get into first and occasionally third gear.

  • (2) Given my experience with this truck thus far, I am willing to spend more for increased reliability. What is the difference in labor time/costs between dropping the transmission to get at the linkage cables versus swapping in something like a remanufactured Ashcroft ?stumpy? R380? (Obviously, there is the cost of the new transmission itself, but I am largely willing to disregard that as this path would enable an upgraded-engine option at some point in the future.)
 

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1of40

1of40

Well-known member
I’d remove the trans tunnel and floor plates to see what’s going on. Couple dozen screws and you’re looking right at it all.
 
nas90tdi

nas90tdi

Well-known member
No cables in the shift mechanism.
Pull your shift boot up and underneath you will see this. Take the 4 13mm bolts out and pull the shifter off.
Check the grub screw near the back. It's likely loose.
The other less likely option is the pin came out of the rear fork. Last picture.

No need to disassemble the floor to check this.

Sorry for the upside down picture. I happened to be near a shifter laying around the garage and just snapped a quick picture.
 

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mitherial

mitherial

Well-known member
As you suggested, the issue turned out to be the the grub screw that connects the main shift-lever to the transmission rod. Easy enough repair once I got over the initial intimidation, but the contact point on the bottom of that screw ( or headless-set-screw) is so small I am concerned that it may come undone again (particularly as the main transmission still requires a fair amount of force to operate). Do people put thread-locker on on this?
 

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mitherial

mitherial

Well-known member
Also, is this brass (copper?) screw with electrical leads at the rear end of the shifter-assembly used for the diff-lock-engaged lamp (which is not currently working on my 90, though I still need to re-check the lamp)?

I went through the parts and workshop manuals trying to figure this out, but went cross-eyed before I found anything.
 

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RDavisinVA

RDavisinVA

Technical Excellence Contributor
mitherial said:
As you suggested, the issue turned out to be the the grub screw that connects the main shift-lever to the transmission rod. Easy enough repair once I got over the initial intimidation, but the contact point on the bottom of that screw ( or headless-set-screw) is so small I am concerned that it may come undone again (particularly as the main transmission still requires a fair amount of force to operate). Do people put thread-locker on on this?
Click to expand...

Yes - there is one flavor of thread locker that is impervious to transmission fluid.
I forget which, but easy to research.
 
R

Red90

Well-known member
That is the reverse light switch. The diff lock switch is facing upon the transfer case.
 
mitherial

mitherial

Well-known member
And less than 50 miles later, the grub-screw/set-screw in the shifter just gave out again, and I just barely coasted into a parking lot to disassemble/reassemble with work lunch break extended an extra hour and a half in the 85 degree weather we're having here.

I will Loctite the grub screw (once a replacement screw arrives as the head on the current one was stripped), and I've ordered new inner gaiter/gaskets for both shifters. And I will replace this little bushing/cup thing (FRC5859), which may or may not make a difference).

Going into D90 ownership, I thought that I had a fairly high pain tolerance for Land Rover related mechanical dysfunction, but this damn truck has travelled less than 500 miles in the almost eight months since I've had it, GAH!
 
rocky

rocky

NAS-ROW Addict
I hear you 500 mile pain. It’s taken months to fix the stalling issue I had. Only done 2000 in five months on mine..
 
mitherial

mitherial

Well-known member
It wouldn't have been a problem if I had gone into this with the "this is project truck" mindset (I thought that I was on the safe side as I got the truck from a very reputable dealer)-- but I guess you have to take the mental attitude that all vintage vehicles are de facto projects, no matter appearance or statements about conditions.
 
mitherial

mitherial

Well-known member
The workshop manual also recommends using Loctite 290 (green, medium strength), but I'm still tempted to use the red high-strength so that that little bleeping set/grubs screw won't come undone again.

It also looks like the nylon bushing cup/sleeve at the bottom of the shifter arm is missing a circlip, which may be contributing to the issue too.
 
mitherial

mitherial

Well-known member
I did! Was definitely a helpful learning experience for someone who had never seriously worked on a car before (and also made me much more familiar with the Parts and Workshop manuals.

The gray plastic bushing/cup was not the issue. Using the Green Loctite on the grub-screw/set-screw (arrowed in attached picture) has held thus far with several thousand KM more on the clock. It definitely needs threadlocker of some kind as it came loose twice dangerously (i.e. can't shift into gear while in motion) until I finally disassembled the shifter-tower myself. It turns out the stupid local shop mechanic had not put any threadlocker on the set-screw when I had them change out the clutch; I also found out later that he did not even bleed the clutch either (!!!); kind of amazing that the clutch worked at all until I eventually flushed it with one of those one-man bleeder setups (I see why as the 19J engine exhaust pipe routing makes bleeding the clutch a real PITA).


Conical Blind Set Screw - Grub screw.jpg
 
mitherial

mitherial

Well-known member
Currently the LT77 transmission is difficult to physically shift into first gear (no grinding, just hard to move the shifter, and very easy to end up in third instead of first), but no issues with other gears. I assume the issue is the first gear synchro, but could be something else. I have tried adjusting the return springs.

Rather than putting more $$$ into fixing it or getting a remanufactured Ashcroft, I have been leaning towards pulling the trigger on a full Cummins R2.8 swap with Uncle Douglas (or some other reputable shop) as the 19J engine itself is getting towards needing a rebuild (which doesn't make sense for that boat anchor), and that swap requires changing to an R380 gearbox anyway.
 
Napalm00

Napalm00

Technical Excellence Contributor
Well I don't want to keep you from upgrading You may just want to dump the oil out of that thing and put in some redline MTF or royal purple synchtomax
 
lcdck

lcdck

Well-known member
Any update on this? I'm dealing with a very temperamental LT77 from 1988. I got stuck in traffic, in NYC, three times when the transmission didn't want to go into any gear. Nothing like downshifting from 3rd, coasting to a red light during rush hour in NYC and not being able to get into 2nd, 1st, nor back to 3rd and then sitting at a green light while three dozen cars behind you honk and yell while you can't go anywhere. It would eventually find 1st but then do it again.
 
Napalm00

Napalm00

Technical Excellence Contributor
lcdck said:
Any update on this? I'm dealing with a very temperamental LT77 from 1988. I got stuck in traffic, in NYC, three times when the transmission didn't want to go into any gear. Nothing like downshifting from 3rd, coasting to a red light during rush hour in NYC and not being able to get into 2nd, 1st, nor back to 3rd and then sitting at a green light while three dozen cars behind you honk and yell while you can't go anywhere. It would eventually find 1st but then do it again.
Click to expand...
Your syncrhos are severely warn. Change the fluid to mtl and save up for a rebuild .

Check the shift tower for wear as well
 
mitherial

mitherial

Well-known member
Per comment #13 above, my issue was the grub/set a screw on the linkage coming loose, fixed by some Locktite—but the shifter was detached from the transmission (completely loose), which doesn’t sound quite like what you’re experiencing. Napalm’s comment re: synchros sounds plausible to me. Best of luck!
 
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