Hi, if the seal went on bench testing I take it from that the axle was not under load so would not be deflected. The shaft could be bent I suppose. The design is fairly simple but I will ask a contact at Poclain who make the axle if he has any ideas. It does not sound as if the pressure is a problem.

The speed of the motor under testing can be critical, if the speed is above the maximum it can affect the motor badly. If only one side turns it can be run at overspeed.

Is there any way the seal could be damaged during assembly by the splines on the shaft?
Lastly, we have had instances in recent years of the seal being displaced from its bore during assembly, could this be possible? If so try loctite, I will try to come back again this week if I get some joy from my contact.

can you send your mail address so I can send a view of the motor to be sure we are talking about the correct seal.

My home mail is [email address removed]

hi,
its been put back together & blew the seal again whilst being bench tested. the shaft isnt worn but we wonder if its bent. the customer has a 2.5 ton loan truck which he says is "unstable & in danger of falling over." they are a scaffolding company with a rough yard full of potholes. the pressure was 20-25psi, ocasionally peaking @ 30psi.

thanks very much for that. i will let you know how we get on.

hi again,
this seal is under the brake pressure which taken directly from the boost pump pressure and fixed at around 20 to 25 bar max, it would be worth checking this for pressure spikes although i would expect this to affect both sides. There should be no high pressure into this area from the motor side as it normally goes into the leakage system and through the cooler and return filter into the tank. I suppose you could check the leakage line from the axle for blockages.

The seal will be affected badly by bearing wear on the shaft support bearings, are these OK? Is the half-shaft worn in the seal running area and the shaft pushed fully home.
The outer half shaft bearing is only grease lubed so can wear out and the leaking oil will wash the grease out.
I suppose you could have been unlucky and just got a duff seal!
If you need more info let me know. I was the hydraulics designer for the old Boss firm and still have a few contacts.

hi,
its the inboard one next to the brake

I am ex Boss and will try to help if I can, which seal is it exactly, the inboard one next to the brake that is supposed to stop oil from coming out of the end of the axle behind the wheel flange or one of the main seperator seals between the high pressure lines?