TB48 Brake Booster Upgrade to GQ 2.8TD

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Originally Posted by nissannewby

Maybe it hasn't been bled properly? Easy to check if the vac is working. Take to vacuum line off and test. Will know pretty quick if there is a change.

A larger master cylinder will allow more line pressure for less effort and the larger booster assists with the increase master volume. It's pretty easy to test brake pressure to see if your at the limits of the gq master. There are also various size masters in the GQ.

GQ brakes are shit when they are at factory tare let alone grossly overweight.

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Thanks Matt, I have a gauge on the vac reservoir, and its pulling down hard. I have not driven it myself, however the mechanic I use and trust is not that happy either. I will make some enquiries with 'The rod shop' in the morning and see what they can offer. their initial thoughts were towards the 4.8 Booster and master cylinder. my issue is the booster is not serviceable as such, and only avail s/h unless I shell out another grand for a new one , which i will do if certain it will deliver the goods. the master cylinder is a slightly larger bore on the 4.8 also. the master cylinder is a brand new factory new unit but for the 2.8 TD engine.

Appreciate the help Matt. this is the final piece of the puzzle on the build so want to do it correctly.

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Originally Posted by Hodge

PeeBee. 4.8 Brake stuff is treated like gold ingots at Patrolapart. You'll be paying through your nose for it. It's very sought after gear. I believe they only have refurbished units ...

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Hodgey, they only sell new master cylinders and s/h booster units, the new ones are pretty dear, but if its what is needed to complete the picture I will buy. What i don't want is to find its not going to deliver. I have gone from 6 pistons to 20 so expect there to be a net increase in clamping force. I am wondering if the new piston seals aare still tight or unlubricated? Clutching at straws, will see what tomorrow brings. thanks for the post.

Plenty of new ones available ex Dubai. But still expensive over there at $965 aud plus freight.

46 Brake Boosters in stock to suit the 4.8.

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Originally Posted by nissannewby

Plenty of new ones available ex Dubai. But still expensive over there at $965 aud plus freight.

46 Brake Boosters in stock to suit the 4.8.

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Thanks Matt, I will see what tomorrow brings. I might take it to a brake specialist at last resort to check the actual pressure. Purchasing new isn't a problem as long as it is the correct diagnosis.

Righto, picked the vehicle up after the pads were removed this morning and de-glazed. The bedding in process for the pads is quite brutal in some regards and I took the vehicle out, following the Willwood Brake bed in procedure where possible. the brakes certainly improved, not quite at 'thru the windscreen' stuff yet, but I ran out of time, so will give them a pounding when I return after next roster. As they are now, they would pull up at 60kmhr in half the distance on patchy dry/wet road - bit hard to lean hard into them as the mud pattern simply locks up. The balance from front to back feels good also. I will see how this progresses, and if required move to the TB48 set-up. Pedal is firm and good feel also.
Only moan is the pads are misaligned by about 2mm on the outer circumference, and after a 30klm trip there was a 0.25-0.5mm brake pad lip. Waiting for a comment from The Rod Shop now.

Rod Shop say the offset is normal for the rears, but not the fronts, so something else to look at. They don't see it as a major, but does not make sense to have a portion of the pad not doing anything. They are recommending the 4.8TB master and booster so will see how I travel with the next roster break, but could be on the cards.

Attachment 83638Attachment 83639

OK, ordered the s/h TB48 booster and new TB48 master cylinder from PAP this morning. Spoke with 'Shorty', very helpful. They are sending it by courier to get around the 5klm rule. Next job is to find the master cylinder and booster as its covered in the usual PeeBee rats-nest of cables.

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Originally Posted by PeeBee

Thanks Matt, I have a gauge on the vac reservoir, and its pulling down hard.

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Hi PeeBee.
Any chance you can post a picture of this vac gauge? Is it under the bonnet or in-cab?

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Originally Posted by BrazilianY60

Hi PeeBee.
Any chance you can post a picture of this vac gauge? Is it under the bonnet or in-cab?

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Attachment 83709

Here you go. It came integral with the larger reservoir. Sits around -23-24 from memory

Not even close to what I was imagining, just for that supercharger nose cone there, LOL. I thought you were talking about that small OEM reservoir.