Vibration and Noise when backing off the gas

**TELF RRC** · 14th February 2012, 09:55 AM

Hi all,

My 1975 Series III SWB has quite a vibration and noise when I back fully off the accelerator. If I back off just a bit, i.e. keep a bit of drive going through its OK. Fine when power is on.

I'm guessing this is either the prop UJ's or a diff or transfer bearing?

Any advice on what and how to check would be great.

Neil

**shorty943** · 14th February 2012, 11:43 AM

Neil, check the UJ's first, they would be the first to go in most cases and the easiest to check and fix, go deeper if they seem to be in good order.

**101RRS** · 14th February 2012, 11:59 AM

"Vibration and Noise when backing off the gas" Does it also happen when you back off petrol. Surely not just an LPG issue.

**TELF RRC** · 14th February 2012, 03:15 PM

Originally Posted by garrycol

"Vibration and Noise when backing off the gas" Does it also happen when you back off petrol. Surely not just an LPG issue.

Har-de-har.

Being the multi-cultural guy I am, I'm using the two terms interchangeably.

**JDNSW** · 14th February 2012, 04:15 PM

A likely problem is a dragging handbrake (usually due to oil contamination) but can also be because it is stuck in four wheel drive or there is excessive free play in the drive line - the bits that matter are the U-joints and loose U-joint flanges.

John

**TELF RRC** · 14th February 2012, 05:27 PM

Thanks all,

I have a couple off UJ spiders in the spares box so I'll check and pop these in. Hopefully the prop flanges are ok. There is a fair bit of oil around underneath so I'll give the handbrake a look too. Seems to be going in and out of 4wd ok so hopefully that's not it.

Cheers, Neil

**wagoo** · 14th February 2012, 09:20 PM

I bought a LandRover Game very very cheaply from a used car yard years ago with the same issue.The yard fitted a reco diff to no avail, so gave up on it. I spotted that the propshaft UJs were 90 degrees out of phase, so after purchasing the vehicle I drove it around the corner, unbolted and rephased the propshaft and had a smooth pleasant drive home.Slack diff Pinion bearings could also be the problem.
Bill.

**TELF RRC** · 20th February 2012, 12:21 AM

New spider in at the diff end and all seems good now. Did find a lot of oil in the handbrake drum. A job for another day.

LWB123 · 25th February 2012, 10:56 AM

Originally Posted by wagoo

I spotted that the propshaft UJs were 90 degrees out of phase, so after purchasing the vehicle I drove it around the corner, unbolted and rephased the propshaft and had a smooth pleasant drive home

Hello from Brisbane.

Found this a genuinely useful thread.

I'm reasonably mechanical but not a mechanic. Could you explain roughly what this means please?

Cheers,

**wagoo** · 25th February 2012, 11:26 AM

Originally Posted by LWB123

Hello from Brisbane.

Found this a genuinely useful thread.

I'm reasonably mechanical but not a mechanic. Could you explain roughly what this means please?

Cheers,

On leaf sprung LandRovers, with the exception of the front of Stage Ones, the transfercase output flanges and the diff pinion flanges are parralell with each other. When the U joints are in correct phase the U Joint cups on the propshaft flanges at both ends of the shaft will be in line and the imaginary line will be parralell with the shaft. The phasing can be altered by separating the telescopic joint and moving the splines around.
On modified vehicles where the flanges may not be parralell then the phasing can be altered by experimentation in order to cancel out vibrations due to having unequal u joint angles. This deliberate out of phasing can be seen on the front propshaft of coil sprung LRs/RRs.
Bill.

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