Hydratrak diff on Griff

[groucho]

I just took my Griff in for a MOT and to find the cause of major klunking to the rear. It turned out to be a duff diff. The final price turned out fairly expensive but he said I had a good deal as the new diff he put on was a fully rebuilt BTR hydratrak diff. Are these much better than normal and how much would you say one's worth?

Could somebody explain what the difference is between the hydratrak and a normal griff diff?

[Ffirg 005]

This has been MUCH discussed and debated in Cerbera (and other) forums so do a search and it will give you the technicalities and the opinions both ways. Consensus from most of those that should know is that the LSD is a better drivers option than the hydratrak, particularly on track. If I was in your situation the price would have to be very, very attractive to make it a good deal.

[groucho]

He told me that the Hydratrak was a fully LSD.

[groucho]

Ffirg 005 said:

If I was in your situation the price would have to be very, very attractive to make it a good deal.

Are you saying that the standard diffs are better?

[bjwoods]

Hydratrak was a cost option compared to a standard diff when new..

B

[shpub]

groucho said:

Are you saying that the standard diffs are better?

Yes. IMHO and experience.

[snap]

The basic difference between the Hydratrak and the Standard BTR diff is that they are both cone type diffs but the hydratrak unit has a much larger LSD unit fitted which makes it much stronger
If we were comparing the Hydratrak to the earlier GKN diff then i would agree that the earlier diff has the edge however the GKN crown wheel and pinion are a weak spot. This is made worse as the parts are no longer readily available for this diff, also the mountings are different for the GKN to the BTR/hydratrack diff and would therefore need modifying . As the Hydratrak is what a lot of manufacturers now use in high powered cars ie Aston Martin in the Vanquish,the Monaro etc then i would go for the Hydratrak if price was ok it is considered to be one of the best all round diffs available at the moment.Not sure what a good price is - new i believe they are around £1400

[GreenV8S]

Hydratrak is a viscous diff rather than a friction diff, and it behaves quite differently and produces different handling characteristics. Personally I don't like them, they don't prevent wheelspin and they feel like a cross between an open diff and a proper LSD. There are pros and cons to each, but if you're an enthusiastic driver I suspect you'll find the friction diff better. The mechanical differences bwteeen the BTR/GKN diffs are a separate issue, the BTR seems to be the stronger diff but that doesn't mean the GKN will give problems.

Having said all that, from the original post it seems that this is all academic since the BTR is fitted now?

[groucho]

snap said:

Not sure what a good price is - new i believe they are around £1400

I got it for a lot cheaper than that. It's a rebuilt one, though. When the weather gets better I'll take it out and see if I can experience the different nuances. One thing's for sure, it's got rid of that horrific 'klunking'

[DarkMatter]

groucho said:

One thing's for sure, it's got rid of that horrific 'klunking'

Can anyone enlighten me as to why they 'klunk', what causes it, and what further problems might you encounter if you ignore it?

Thanks. Andrew.

[gingerprince]

The klunk is more often than not caused by worn mounting bushes (there are 3, one at either side and a top one which is "a reet bugger" to get to!

[DarkMatter]

gingerprince said:

The klunk is more often than not caused by worn mounting bushes (there are 3, one at either side and a top one which is "a reet bugger" to get to!

Thanks gingerprince, I have heard that the bushes wear, or that the mounting bolts can loosen, and also that the propshaft/diff flange bolts can loosen (mine were).

I'm curious though, to know what it is that goes wrong with the diff which causes the 'clunk', and what is renewed during a diff rebuild to fix it?