Jacking under the diff

[jerrytr5]

In the sidescreen forum there is a thread about jacking points and I was corrected when I suggested that under the diff casing was acceptable. Doing so causes strain and oil leaks on these cars.

Is the 7 rear axle similar in construction to the early cars, or am I ok to slap a trolley jack under the diff?

Thinking about it, all my cars have either been independent or FWD. Apart from a Scimitar this is my first live axle car (and I'm not even sure the Scim counts as live).

Jerry

[RobH]

All solid axle casings are made in a similar way.  Some are stronger than others but It's never a good idea to jack under a diff even though a lot of people do it - including tyre depots.

 

 

 

Edited September 26, 2023 by RobH

[jerrytr5]

One never stops learning

[DaveR]

Problems can be caused if a jack with a small cup/pan is used under the diff housing as it can dig in. Jacks with a large cup/pan is less likely to cause damage. But, you still need to be careful.

Dave 

[RobH]

7 minutes ago, DaveR said:

Jacks with a large cup/pan is less likely to cause damage. But, you still need to be careful.

The potential for damage is less due to denting the diff housing itself  but more the strain on the joints between the axle tubes and the housing.  There is considerable leverage there due to the length of the tubes.  Was the joint designed for this loading ?

 

[DaveR]

23 hours ago, RobH said:

The potential for damage is less due to denting the diff housing itself  but more the strain on the joints between the axle tubes and the housing.  There is considerable leverage there due to the length of the tubes.  Was the joint designed for this loading ?

 

Agreed, there is unwanted loading on the diff tubes. The additional problem with the TR7 is the rear cover is easily damaged by the claws on the jack cup/pan.

Dave

Edited September 28, 2023 by DaveR

[Wayne Scott]

Surely, on a live axle suspension set-up like the TR7, if the axle tubes cannot withstand that sort of loading, we have a bigger issue at hand than anything to do with jacking!? 

[BlueTR3A-5EKT]

4 speed and 5 speed axles are completely different construction. 
The 5 speed is constructed not unlike a sidescreen car axle with steel tubes retained in a cast centre case.  This axle is derived from Rover SD1 cars

The 4 speed is essentially a Morris Marina axle.   The main case and tubes are all pressed steel and weld fabrication.  The differential bit is cast construction and is bolted into the axle case.   The MG people call this a banjo axle.  
 

To strengthen the banjo axle Lotus tuners would weld a strip of steel along the top of the axle tube either side.

Edited September 28, 2023 by BlueTR3A-5EKT

[RobH]

In normal use there is minimal loading of those joints in shear other than from the weight of the differential. The main load will be  torque reaction.  Small compared to the weight of the rear of the car times the 'lever' length.   We are also not talking about actual failure of the joint - just oil leakage as a result of deformation under stress.  

[DaveR]

22 hours ago, BlueTR3A-5EKT said:

4 speed and 5 speed axles are completely different construction. 
The 5 speed is constructed not unlike a sidescreen car axle with steel tubes retained in a cast centre case.  This axle is derived from Rover SD1 cars

The 4 speed is essentially a Morris Marina axle.   The main case and tubes are all pressed steel and weld fabrication.  The differential bit is cast construction and is bolted into the axle case.   The MG people call this a banjo axle.  
 

To strengthen the banjo axle Lotus tuners would weld a strip of steel along the top of the axle tube either side.

The diff used on the 4 speed TR7 was derived from the Standard 8/10, Triumph Herald, Triumph Vitesse, GT6 and Spitfire. As was the 4 speed gearbox. The rear TR7 suspension live axle layout was derived from the Triumph Toledo (introduced in 1970) which used the same type of 4 speed diff. In order to reduce the number of different diffs/gearboxes BL used both the Standard Triumph (ST) small car diff and gearbox on the Morris Marina. It was adapted from three rail to single rail gear selection with some other changes for the Marina. ST's Harry Webster was by then in charge of Austin Morris engineering. I can remember the publicity at the time that the Marina was using Triumph parts. By 1975 the Toledo, Spitfire and 1850 Dolomite (not the Sprint) had gone over to using the single rail set-up. The original Herald gearbox and diff were beefed up and given synchromesh on first for the GT6/2 Litre Vitesse and these were used in the 1970's models. As interest the diff ratio of the TR7 4 speed is the same as the Spitfire 1500 and 1850 Dolomite. i.e. 3.63. The good old parts bin. The gearboxes were adapted to suit the different models and hence are not all interchange.

I'll get my anorak, Dave

[BlueTR3A-5EKT]

3 hours ago, DaveR said:

The diff used on the 4 speed TR7 was derived from the Standard 8/10, Triumph Herald, Triumph Vitesse, GT6 and Spitfire. As was the 4 speed gearbox. The rear TR7 suspension live axle layout was derived from the Triumph Toledo (introduced in 1970) which used the same type of 4 speed diff. In order to reduce the number of different diffs/gearboxes BL used both the Standard Triumph (ST) small car diff and gearbox on the Morris Marina. It was adapted from three rail to single rail gear selection with some other changes for the Marina. ST's Harry Webster was by then in charge of Austin Morris engineering. I can remember the publicity at the time that the Marina was using Triumph parts. By 1975 the Toledo, Spitfire and 1850 Dolomite (not the Sprint) had gone over to using the single rail set-up. The original Herald gearbox and diff were beefed up and given synchromesh on first for the GT6/2 Litre Vitesse and these were used in the 1970's models. As interest the diff ratio of the TR7 4 speed is the same as the Spitfire 1500 and 1850 Dolomite. i.e. 3.63. The good old parts bin. The gearboxes were adapted to suit the different models and hence are not all interchange.

I'll get my anorak, Dave

Thanks for that

[andytr]

So where is everyones recommended jacking points front and rear please?

[TR8IAN]

I've been jacking my TR8 under the diff for the last 30 years - never had any issues. Have a Sealy professional jack with a big cup.

I tend to lift the front under the sub frame or the more substantial chassis parts. I have two low ramps made from 50 X 200 mm wooden planks about 700 mm long this allows and easy access under the car and is safe whilst I'm lifting before adding jack stands.