"CLUNK" from transmission

[AJM90V8]

Now that my vehicle has an MOT and I am driving it again...

It seems there is some play in the transmission somewhere which can make a noticeable clunk if I am not careful changing gear. In fact if I am driving on the level and accelerate-decelerate it is quite definite.

Obviously there are quite a few candidates - does anyone have any suggestions for a technique to identify where the problem is? I would say, more towards the back than in front, that's about all I can tell so far.

Thanks!

[ejparrott]

What transmission is it? If its early LT77/LT230, pop the PTO cover off and check the output splines...

Things also to check are A frame bushes and trailing arm bushes, and make sure the UJ's aren't shafted.

[need4speed]

Rear prop uj?

[Tanuki]

Propshaft slip-joint splines?

Hub drive-flanges?

Front CV Joints?

[firesden]

also check rear diff play

[robertspark]

Which engine and gearbox do you have? (Take its a rover v8 so the spline wear on the gearbox output shaft and the transfer input gear is a high candidate)

[need4speed]

Which engine and gearbox do you have? (Take its a rover v8 so the spline wear on the gearbox output shaft and the transfer input gear is a high candidate)

Why would this kind of wear be more likely on a v8?

The rv8 is known for being very smooth, and with that being the case offers less shock through the transmission. Im not saying the output shaft/input gear ISNT worn, just that i dont see it being more likely if its a v8 unless its a hugely powerful one..

Id still be checking prop uj's first.

[robertspark]

Sorry, did not see the response earlier....

I'll speak from my experience / point of view only, but I guess it could be applied to other engines and gearboxes too.

3.5 rv8, su carb'd, LT85 + LT230 (c suffix).

upon stripping my vehicle which had a pronounced clunk (and at the time of my stripping it a very bad 5th gear rumble too (apparently well known in the LT85's because of a combination of high speed running in 5th gear and a lack of bearing support for the 5th gear (long output shaft, with a 5th gear on it and a single bearing support to the 5th gear))

when I split the transfer box from the gearbox, I was surprised by the amount of spline wear ( a step) that had been formed in splines of the gearbox mainshaft and the transfer case input gear (I would have said about a 50% step).

Seems to be referred to as the knock of death here: http://www.defendersource.com/forum/misc.php?postid=108984&threadid=13712&external_page=http%3A%2F%2Fwww.landroverclub.net%2FClub%2FHTML%2FDefender_problems.htm

Another example here: http://www.aulro.com/afvb/technical-chatter/37886-lt230-input-gear-again.html

What surprised me even more was the shortness of the gearbox output splines and that the transfer case input spline was not fully splined which would have reduced the amount of pressure being transmitted through the splines (force / area = pressure).

Now you need to bear in mind that this was an '89 landrover 90, and was a suffix C transfer case, so the input gear is not cross drilled (as standard) (FRC8917) and it appears that the suffix D transfer case input gear (FTC5089) has both a cross drilled input gear to provide better lubrication of the splines and has a longer section of spline.... The longer spline statement is something which I've not quite been able to prove but if you compare the input gear adapter used for the ZF coupler shafts (FTC5090 - long shaft [can't seem to get the number for the short spline one, although the comparison between the two is in this link)

http://www.defendersource.com/forum/showthread.php?t=13712

The reason why I've not been able to confirm the longer spline statement with regards to the input gear is because I bought a FTC5089, which sure enough arrived cross drilled, but the thing has the same internal spline length as the FRC8917 I took out which is not helpful for what I need to do next in my build which is to respline it for a chevy 32 spline mainshaft (EDM wire machining), hence I wanted as much metal available as possible as I don't want to have this problem in the future (I may end up getting an input gear bespoke made in the end).

The other issue is that the input gear is case hardened, so the advice / comment at the time was once it begins to wear and breaks the case hardening layer it's goosed because it then gives it a running start when you change gears or take up play in the rest of the drive trane, especially as the underlying gear material is softer.

You also need to bear in mind that at the time of the rover v8 used in the defenders it had the most amount of torque and horsepower of all the other / previous rover powerplants used prior to this (135HP (on SU's) / 185 lbft) (on the LT230), so the weak bit from my observation was the gearbox output shaft and the transfer gear input splines, something that appears landrover knew about / discovered in service when it issued the later LT230 D suffix where the input gear was changed to crossdrilled plus the ZF adapter shaft was changed to a longer spline variety.

http://www.ashcroft-transmissions.co.uk/diy-rebuild-kits/zf-rebuild-kits/ftc5090.html

Why, or why did they choose to only partially spline the LT230 input gear I cannot fathom (note: I'm not a gear expert / any sort of fitter and turner so I'm sure there was a good reason), but a fully splined input gear, with a corresponding longer gearbox mainshaft longer output spline would (in my uneducated layman's opinion) have reduced the pressure experienced at the spline joint (plus made my life easier resplining it for even more torque!)

The rover v8 is a smooth engine, and even smoother with an auto box to smooth out the gear changes and acceleration from a standing start, but in a manual defender (my experience anyway) it seems to increase any drivetrane wear and develop a cluck at the input gear.

UJ wear, is listed here as causing a clunk too : http://www.repairmylandrover.co.uk/defender-repairguides/guide-to-defender-propshaft-uj-replacement

this however should be easily diagnosed whilst laying under it and inspecting the propshafts.

Rob

[AJM90V8]

Thanks for all the thoughtful replies!

Foolishly posted this in my MOT-pass enthusiasm just before going away on holiday; so sorry for appearing to ignore everything. Back now and I'll be on it over the next few days. Will definitely post what I find.

PS: my vehicle is a "D" reg V8, LT85/LT230 mostly original running gear though with chassis & body rebuilt.

Don't remember such a clunk before I SORN'd it...

[AJM90V8]

To cut the story short: while checking various as suggested I found that the nut holding the upper arm ball joint (if I have the terminology right) to the axle was loose. Not just loose but halfway off - and with no split pin in place.

Totally amazed by this because I do almost all work myself - but after an MOT issue just before I SORNed the vehicle I had it replaced professionally....

So a spanner and a split pin fixed this issue in no time at all.

So first prize to ejparrot for being in the right area without actually hearing the "clunk"