All,

96 D1 has ~150k miles on it with a R380, and has some low speed issues with drive-train play, along with occasional high speed clunks, specifically off throttle deceleration.

Situation #1:
Sub 15 mph on the street. 2nd gear. Accelerate at mild pace, let off accelerator pedal. The truck will rock back and forth with clunking noises. The RPM of the engine actually "see-saws" as it decelerates. Sometimes this occurs violently, other times in a more mild fashion. Declutching always stops this motion immediately and is often required. Giving the truck more throttle also causes this to stop.

Situation #2:
I use this truck for off road trips so it spends a lot of time in low-range. This rocking motion is particularly bad in low range, again only occurs when transition from throttle to off throttle. It is often so violent that it upsets the truck and feels like I am riding a horse. Definitely makes it very difficult to navigate obstacles in 1st gear, or drive down the trail in 2nd and 3rd. **Important to note, this does not seem to occur in long down hill sections where I am in 1st and using engine breaking. Seems to occur only in on throttle to off throttle transition. When I declutch in these situations (when rocking) I often get a quick rattle from what sounds like the front output area of the transfer case, but again difficult to tell (even when I reproduced it with the trans tunnel cover off).

Attempted Diagnosis/Repairs:
Had buddies listen outside the truck as I duplicated the issue, they stated that the clunking/clicking noise seems to come from the transfer case/transmission area. The rear upper a-arm balljoint was shot, replaced that with a new unit. Greased all u-joints and replaced transfer and transmission fluid about 3 months ago. Mounts for the transfer case/transmission look used but not broken. No noticeable movement of the shifter during rocking which suggests the physical drivetrain components are not moving (not a shot mount). Engine mounts are in good shape. No noticeable play in DS u-joints.

My leading suspicion is transfer case wear, though I have read about output shaft wear for transmissions as well. My R380 seems to be in good shape (no real grinds to speak of and shifts well), however my transfer case is fairly noisy. Especially at higher speeds on acceleration (high pitched whine). Have any of you experienced similar symptoms? It has definitely gotten worse since my last offroading trip and is incredibly frustrating when trying to keep control over your vehicle.

 

I have these issues. The exact behavior you describe, bucking and off throttle issues, both low and high speed, clutching in stops the issue. Essentially that bucking feeling is the drivetrain bouncing off of itself from play in your drivetrain. It is not present to the same extent in Automatic models as the nature of the trans covers up some of this slack in driving. In my limited experience, the gas V8 makes this behavior much worse with power input, and while the behavior exists on diesels, for whatever reason even with excessive play I have never experienced it as bad in any diesel versus gas. Thus its the worst on the NAS 5 speed discoveries

The off road rattle behavior you describe I also have experienced, seems like the play will bind up in spots and if you clutch in that bind will let up suddenly and rattle or pop. On this and another vehicle especially with diff lock on if you clutch in you definitely get a rattle if there is any binding up (usually in a turn, wheels not straight).

On mine both front and rear differentials have significant play and are the likely cause of my issue. I have a new trans and transfer box so your may have an issue there on your D1, but put it on a rack and check everything.

some or all of these together can cause what you describe
>transmission output shaft spline wear (can pull the PTO cover off the transfer box to inspect this for play)
>transfer box wear at outputs or internal
>engine/trans/transferbox mounts (looks like you addressed that check)
>prop shaft play (usually found and corrected first)
>differential play at axles
>axle shaft play at splines or inside diff
>drive member play (worn splines)

Best of luck. The rubber banding is quite possibly one of the worst driving experiences.

 

With your mileage start with the front axle hubs, then CV's, then both diffs, driveshafts, transfer case, transmission in order to find/remove the big offenders. It doesn't have to be a right now thing and can be done over a long period. The 4.0 has large counterweights for it's displacement, it's made to lug low, not high rev/quick response. The drivetrain relies on it's guts to make up for the small motor displacement horse power and torque. There are design issues with both the LT230 and the R380 and there are remedy parts. Give this site a read, has some good info on those two boxes - http://www.ashcroft-transmissions.co.uk/index.php The driveline "clunk" is also present with the auto's when on/off the throttle and so is the driveline wrap. I would lock/unlock 4 high often due to where I live on a daily basis in the winter and the transfer case was always bound so a quick unwrap with trans in neutral would unwind everything.

 

Thanks for the thorough responses guys. Been doing some reading on both the Ashcroft website and watching on the Land Rover Toolbox (via youtube). I neglected to mention that I did replace the front drive flanges, though the wear was negligible on the original units/CV. There is definitely a little wear in the rear diff, but nothing substantial. Based on some of the videos and pictures I have seen I am fairly certain I have lt230 input shaft and/or R380 output shaft spline wear. Plus some backlash issues in the transfer box most likely due to wear (also results in noise/whine). Once I get the truck back from the shop I am going to pull the PTO cover and confirm. I have a spare transfer box from the parts truck which is in better condition, so if I can confirm it is input shaft wear, at least then I know I can do a replacement. If I have bad output shaft spline wear on the R380 it could be goodbye to the rovers as that would require a full rebuild of the unit. Best case scenario this is caused by lt230 input shaft spline wear and there is no real damage to the R380 output shaft splines. Then I would be able to simply swap my other lt230 on, though I might consider replacing the input shaft with a cross drilled unit from Ashcroft (with fresh bearings) to prevent it from wearing in the future.