Disco isn't dead... not yet.

LRNAD90

Adventurer
So not sure of your background, but there is a very well known, documented issue with the output shaft of the transmission/input gear of the transfer case, and it usually manifests itself as a whine at speed. I've been through it with a '96 Discovery, so I have first hand experience. There is an issue with enough lubrication getting to the splines of the output shaft, which results in excessive wear. Land Rover had multiple TSBs on the issue, initially installing a 'splasher' to try to force more lubricant to this interface, which is a high point in the TransferCase.

You won't see the issue removing the bottom plate as you have shown. You have to pull the rear PTO cover and pull the input gear (Check out this Thread on the D90 Source for some photos of the issue, but search over there, and there are multiple threads on the issue).

Land Rover's final solution was an input gear that is cross drilled to provide an easier route for oil to get to these splines, and they also lengthened the spline area on the input gear to distribute the load better. Some have had luck with using a heavy duty grease on the splines, and others swear by overfilling the Transfer Case, theory being that the increase oil level gets more oil to the vulnerable interface..

The Good news is that the Input gear is an easy swap, the bad news for Manual Gearboxes is that to repair the output splines, requires replacing the output shaft of the Transmission, which of course requires a full rebuild (auto Gearboxes had a stub shaft on the back of the Auto Gearbox that could be easily replaced, but no such luck for Manual gearboxes)

Next up was the transfer case, especially with the whine I was getting on the highway while cruising. Here is what I found when I pulled the drain plug. Definitely not ideal, but no huge chunks either. The fluid was a dark, dark brown so it was clear it had not been changed for a long time. I looked over the gears in the transfer case and while there was definitely wear I did not see any chipped teeth so I proceeded.

View attachment 506650

Yeah.. it should not be that color...



View attachment 506651
 

DiscoDavis

Explorer
Dude you must have bought the siamese twin of my car. Same issues and more back then. Lol at the gas vent hose, I had the same experience first time I pumped gas!

Good luck and best
 

_ExpeditionMan

Adventurer
So not sure of your background, but there is a very well known, documented issue with the output shaft of the transmission/input gear of the transfer case, and it usually manifests itself as a whine at speed. I've been through it with a '96 Discovery, so I have first hand experience. There is an issue with enough lubrication getting to the splines of the output shaft, which results in excessive wear. Land Rover had multiple TSBs on the issue, initially installing a 'splasher' to try to force more lubricant to this interface, which is a high point in the TransferCase.

You won't see the issue removing the bottom plate as you have shown. You have to pull the rear PTO cover and pull the input gear (Check out this Thread on the D90 Source for some photos of the issue, but search over there, and there are multiple threads on the issue).

Land Rover's final solution was an input gear that is cross drilled to provide an easier route for oil to get to these splines, and they also lengthened the spline area on the input gear to distribute the load better. Some have had luck with using a heavy duty grease on the splines, and others swear by overfilling the Transfer Case, theory being that the increase oil level gets more oil to the vulnerable interface..

The Good news is that the Input gear is an easy swap, the bad news for Manual Gearboxes is that to repair the output splines, requires replacing the output shaft of the Transmission, which of course requires a full rebuild (auto Gearboxes had a stub shaft on the back of the Auto Gearbox that could be easily replaced, but no such luck for Manual gearboxes)

Thanks for the input, this is exactly the kind of stuff I hope to gain from the members here! The build thread is about 6 months behind real life and your comment was exactly the consensus I came to based on my own research several months ago. I have a plan to confirm and potentially repair which is dependent on the condition of the R380 output shaft splines. I will get this thread up to speed sometime soon and then we can compare notes.
 

_ExpeditionMan

Adventurer
Dude you must have bought the siamese twin of my car. Same issues and more back then. Lol at the gas vent hose, I had the same experience first time I pumped gas!

Good luck and best

I tried buying the EXACT same truck as yours (now the parts truck) before this one. Still haven't added that little adventure to the thread. Can't decide if all of these trucks were completely trashed by their owners or just poorly made. It can't possibly be the second one though! haha
 

LRNAD90

Adventurer
a 96 should have the cross drilled input gear already. My 95 did.

The whine could be the rear bearings in the r380. Does it do it in all gears?

Not from the factory, they weren't fitted until '97. My '96 Disco didn't have one..
And my '95 D-90 didn't..

TSB's issued in '96 were still spec'ing the installation of the 'oil feed disc'..

Here is the Text of the Spline Wear TSB issues by Land Rover:

"Gearbox Mainshaft Spline Wear

Issue 2

24/05/96

37/02/96/US

SUBJECT:
Gearbox Mainshaft Spline Wear

MODEL:
Discovery
Discovery
Defender 90

AFFECTED VEHICLES:
LPLJ 178205 Onwards
LJ 506525 Onwards
LD 976480 Onwards

DETAIL

Some customers may complain of clonks and backlash in the transmission system. This may be due to gearbox/mainshaft spline wear. The clonk/backlash will be most apparent in stop/go traffic under overrun conditions or when maneuvering the vehicle during parking, etc. From transfer box numbers 28D460996 F (Discovery) and 22D 461124 F (Defender) all factory built LT230 transfer boxes have a revised design of input gear, featuring lengthened splines and cross drilled oil feed holes. This modification eliminates the
requirement for an oil feed disc (bulletin H415) and eliminates input gear/mainshaft spline fretting/wear. Coincident with this change, the transfer box identification number has been changed to Suffix "F".

Information only:
The new parts supercede all old parts and should be used in ALL LT230 applications during repairs.

NOTE: Do not use in conjunction with an oil feed disc, Bulletin "H415 Mainshaft Spline Wear Prevention." If a complaint of transmission clonk/backlash is made, it is likely mainshaft spline wear has occurred. The
transfer box mainshaft input gear and gearbox mainshaft must be replaced together as a pair.

ACTION REQUIRED

If a customer complains of transmission backlash/clonk refer to the
procedure below.

PARTS INFORMATION

Mainshaft/Input Gear replacement part numbers
Manual R380
FTC5087 replaces FTC4188, ratio 1:1.214,28 teeth
(Defender and Discovery)
FTC3703 - Gearbox Mainshaft (Defender and Discovery)

ZF Automatic
FTC5087 replaces FTC4188, ratio 1:1.214, 28 teeth
(Defender and Discovery)
FTC5090 replaces FTC3981 - Coupling Shaft (Defender and Discovery)

PROCEDURE

Follow procedure outlined in Workshop Manual Section 37 "Manual Gearbox", Section 41 "Transfer Box", and Section 44 "Auto Gearbox."

For ZF Automatics: When coupled to a ZF Automatic gearbox a new coupling shaft is required with extended splines. This is a factory fix for all Discovery Automatics and LT230 transfer boxes.

NOTE: If the clonk/backlash is thought to be coming from the transfer box, remove the power take off cover and bearing housing from the rear of the transfer box to inspect the input gear. Visually inspect the transfer box input gear and the gearbox output shaft if visible wear is evident, the gearbox output shaft and the ransfer box input gear will need to be replaced as a pair.

WARRANTY:

Normal warranty policy and procedures apply.

COMP.CODE:

3L9J

SRO:
37.20.88/26 - Input gear and mainshaft (manual) renew 10.50 hr.
44.20.88/26 - Input gear and coupling shaft (automatic) 7.00 hr."

Here is the Oil Thrower 'fix' TSB as well, issued before they started using the crossdrilled input gear:

"You have the oil thrower fix if there is a yellow X painted on the back of the T-case. None of the fixes can be done with an LT77s. This is the PREVIOUS fix. Mainshaft Spline Wear Prevention

29/03/96

H415

SUBJECT:
Mainshaft Spline Wear Prevention

MODEL:
Discovery - with R380 Manual Gearboxes
Defender 90

AFFECTED VEHICLES:LJ 081991 to 172377
LJ 500000 to 504330
LD 939976 to 972378


DETAIL

To prevent occurrence of mainshaft spline wear, an oil feed disc has been introduced into the LT230 transfer gearbox which can be retro-fitted to earlier vehicles providing a customer complaint of transmission backlash/clunk is not evident This disc is a preventative measure only and will not cure existing spline wear induced "clunk" without other component changes. All transfer boxes from the above VIN numbers LJ72378, LJ 504330 and LD 972378 that are fitted with a feed disc at the factory are identified with a yellow "X" painted on the power take off cover so external confirmation of repair is visible, dealers should also apply this paint identification to identify completion of repair and to prevent this work being carried out again.

NOTE: Vehicles fitted with a LT77S manual gearbox CANNOT utilize this fix. Transfer boxes from suffix "F" will be fitted with a production solution which entails additional oilways in the transfer box input gear (detailed in Bulletin 37/02/96/US). Vehicles fitted with suffix "F" gearboxes cannot be fitted with the oil feed disc.

ACTION REQUIRED

At the earliest opportunity fit the parts listed below to all R380 vehicles, providing no customer complaint of backlash/driveline clunk is evident.

PARTS INFORMATION

FTC4993 - Oil feed disc (Qty. 1)
FTC4994 - "0" ring (Qty. 1)
STC611K - Hylosil sealant (Qty. 1)

NOTE: This fix cannot be fitted to LT77 or LT77S manual gearboxes.

PROCEDURE

See Workshop Manual for removal of the P.T.O. cover and bearing plate.

1. If during fitting of the oil feed disc, advanced spline wear is noted, both the gearbox mainshaft and the transfer box input gear should be replaced (if the replacement transfer gear has oil holes into the spline, an
oil feed disc will not be required, see Bulletin 37/02/96/US).
  1. Assemble "0" ring onto disc and locate disc into bearing housing ensuring cut outs are aligned and disc ID "TOP" is at the top of the disc.
  2. Rebuild referring to Workshop Manual, cleaning off all traces of old sealant.
  3. Paint a yellow "X" on the power take off cover.

Note: Do not rebuild with grease - if spline lubrication is required, use only transfer box oil.
NOTE: For guidance on repairs to resolve customer complaints of transmission backlash refer to Technical Bulletin 37/02/96/US.

WARRANTY:

Normal warranty policy and procedures apply

COMP.CODE:

H415

SRO:

H415 - Fit oil feed disc 0.90 hr.

NOTE: If any additional mainshaft wear is noted replace parts and claim
through normal procedures."
 

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