GU 2.8 pulling 4600 rpm at 110kmph

[Johnmadeley]

Hey all, I have recently purchased a 1998 2.8 wagon from a car yard, when I got it on the highway it holds 4500-4600 rpm in 5th gear at 110km, any ideas why is would be revving so high? It drives normal but is just pulling bulk rpm! It has 33's and has done 190,000 . I would have thought they did 3000.. ? Help

[the ferret]

Sounds like the rev counter is us mate, shouldn't be pulling those kind of revs, If you jump over to introductions and tell us a bit about ya self, there might be more responses to your question.
Welcome to the forum mate.
Cheers, the ferret.

[nissannewby]

Possibly your tacho is cactus

[Johnmadeley]

its not the gauge I can hear the engine defently revving more then 3000 rpm, I will do that soon cheers mate. It's gone back but I need an idea because I don't want the car yard to try do me over and pay for repairs

[the evil twin]

Uuummmm, that is almost exactly double the RPM you should have for a 2.8 on 33's at 100 ish KPH real speed (allowing for some speedo error).

Are you sure the engine is doing 4600?... It would be howling it's heart out... I would have said the tacho is shagged same as the other guys

If it was an auto then I'd say you have one stuffed tranny but in 5th gear in a manual the only other explanation would mean that the diff ratios must be... like... 8.0:1

[nipagu7]

slipping clutch perhaps ?

[BigRAWesty]

Check your diff ratios. Possibly bolted in 4.6 centers and stuffed the ratio.

[the evil twin]

slipping clutch perhaps ?

Possibility but if it was slipping 2,000 RPM down the freeway I reckon it would have only lasted about 500 metres


Check your diff ratios. Possibly bolted in 4.6 centers and stuffed the ratio.

It's a 2.8 so it already has the highest stock diff ratio (4.62).
Can't be some weird rrse mod to the transfer case high range can it?
Could possibly be the truck was a lemon and stuck in low range but it would do, like, 2 KPH at 5000 RPM in first (joking, but you get my drift)

Hey John,
What is the vehicle idling at on the Tacho and are any of the other gears exhibiting similar symptons

[BigRAWesty]

Possibly an old 3ltr with 2.8 engine and box dropped in. That would throw the ratios out..

[the evil twin]

Possibly an old 3ltr with 2.8 engine and box dropped in. That would throw the ratios out..

Hiya Cobber,

Yeah but unles my maths are out (which happens a LOT) then the ratios would be taller wouldn't they... and the engine revs would be too low?

Your right if it was a mod the other way... a 3 litre or 4.2 into a 2.8 shell and diff

It's definitely a weird issue if it isn't the tacho eh Westy

[TimE]

4600 rpm in 5th gear in my GU IV with 33s and I'd be doing 218 kph !!! Haven't seen that sort of speed since my old Greg Norman Statesman.

[nissannewby]

Even a 4.2 with 4.6's and 33's won't get to 3000rpm at 110. A 2.8 won't bolt to a 4.2 or 3.0 box so can rule that out. If it's revving at that at 110 you would be shifting gears like nothing else before getting to 5th lol

As evil twin said if the clutch is slipping and these revs have been held then it would now be cactus and now not be functioning lol.

I know if at 3000rpm most diesels do sound like they are fairly revving.

[the evil twin]

Gotta agree, Cobber...

OP was fairly adamant the revs were genuine but I'm not convinced yet. The 2.8's get their tacho feed from a sensor in the fuel pump don't they?

OP has the car back with the yard ATM so I guess we wait and see what happens next...

[trekster]

Mine 2.8 sits at about 2800-3000ish at 100km/hr and that is with 285s

[Johnmadeley]

Thanks guys it's at the workshop now getting a new water pump so once they can drive it I will update you on what happens