Hi I have just signed up to join this forum so I guess I'm a newbie hope I do this right I have a 2.5 diesel Trojan it seems to have a flat spot on pulling away then seems ok but will not go over 70mph any ideas

Not really much to go on, What age of Trojan?, Have you just bought it or has it just started doing it? When was it last serviced?

Firstly this is a two and a half ton commercial truck and which is low geared and although it should do 70 without much issue it won't go that much further, starting point has to be a new fuel filter and fuel cleaner.

It's 2001 have had it about five years last serviced about 5 months ago. Has only recently started doing it I have replaced glow plugs as it was also getting hard to start. Glow plugs seem to have sorted the starting problem but nothing else. I have put a diesel treatment in it aswell

It sounds fuel or timing related is there any noises or smoke coming from it if so what colour.

Change the fuel filter and put in a bottle of forte advanced diesel treatment,
When did it last have a timing belt, it's possible the belt has jumped a tooth also check your bottom crank pulley if it's wobbling get it changed straight away

It is smoking a dark grey smoke had belts done same time as service if will try changing fuel filter and add some of the stuff you suggest thanks for your advice [Thanks1]

Grey smoke suggests unburt fuel which could be one of several things, but does sound as if the belt has maybe jumped a tooth, try the fuel filter first and take it from there, as I said have a look at the crank pulley to ensure the pulley hasn't delaminated or the bolt snapped

Thanks for your help will try all your suggestions

Thanks for your help will try all your suggestions

No worries chief, why not register on the forum properly and you'll have access to the entire technical section, it's completely free and very worth while

I have registered just waiting to be accepted think this forum could be very helpful

could be overboost