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RogerH

4A diff front plate oddity

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Hi Folks,

               if you look you will find.

I looked and found that the mounting holes on the diff are not regular.

The front near side hole ( on the front plate) is 1/2" out.

The pins appear to be in the right place - apprx 13" apart (fore/aft) but the place appears skewed with the nearside 1/2" longer.

 

Now, here is the $64,000 question - would this mis-alignment cause a clonking around the diff area ?

 

I wonder what I'll find tomorrow.

 

Roger

  

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Hi Folks,

            the mystery is raveling in front of me. 

The offside corner of the diff front plate (item #93 https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/clutch-transmission-drivetrain/axles-differentials/irs-rear-axle-differential-tr4a.html) has broken twice - see pic below.  

I blamed my welding after the first failure.

However it would appear that the front plate has been distorted from the year dot.

The rubber bushes would force it back into alignment but input residual stress on the corner.

With the rigours of diffing the stress cause the corner to crack.

Using one of my more delicate hammers the front plate is now straight (ish)

 

BUT the mystery is that it was the front nearside that was out of alignment - was this transfering the stress to the other side !!

 

The diff is fitted and looks good (at the moment).

Roger

 

 

Camp06 025.jpg

Edited by RogerH

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Hi Pete,

           no I didn't do that. The pins looked good and equi-spaced.

Before the bottom big washers went on the pins were in the centres of the mounting holes.

 

Roger

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Hi Pete,

        the pins were in the middle of the holes ONLY after I teased the nearside hole corner of the plate rearwards 1/2".

Before my little teasing the nearside was too far forward by 1.2"

 

How that could cause the offside to break (twice) is beyond me.

 

Roger

Edited by RogerH

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Hi Roger, the near side of the rear prop shaft UJ is much closer to the tunnel than the offside (at least on my car it is) so much so that on worn or soft rubber mounts the UJ can knock on the tunnel when executing RH turns. Someone may have bent the bracket to provide more clearance for the UJ. On my car the knock was fixed by fitting new standard rubber mounts.

Chris

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Chris is on the button, I've seen 2 TR4a with offset transmission tunnels to the propshaft close enough so that upon cornering or body lean there's a definite ggrrrouunnnch as the prop spider helps the clearance on the tunnel !

Mick Richards

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My original rubber bushes were fine but while the diff was out I cleaned them using WD 40 and a rag, this caused  the rubber to go soft and the diff to move about too much. So with any rubber items which are loadbearing only clean using soap and water!

Chris

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I have a 4A and had the diff overhauled last year.  When refitting it I used poly bushes - and the prop shaft u/j knocked on the offside in corners.  Refitting the earlier fitted rubber bushes cured the problem.  I have always assumed that the reason the prop shaft was offset in the tunnel was because the body was misaligned when fitted to the chassis - by whom and when I know not, as I have only had the car about 12 years, but it was restored in 1992.  However, I did wonder whether it implied a bent chassis or whether whoever last fitted the body decided near enough was good enough..

Geoff

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14 hours ago, Horse said:

I have a 4A and had the diff overhauled last year.  When refitting it I used poly bushes - and the prop shaft u/j knocked on the offside in corners.  Refitting the earlier fitted rubber bushes cured the problem.  I have always assumed that the reason the prop shaft was offset in the tunnel was because the body was misaligned when fitted to the chassis - by whom and when I know not, as I have only had the car about 12 years, but it was restored in 1992.  However, I did wonder whether it implied a bent chassis or whether whoever last fitted the body decided near enough was good enough..

Geoff

The prop is slightly offset anyway as the diff nose is off to one side.

Stuart.

 

Tonys TR6 464.jpg

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