RD28 to TD42 conversion - revs too high HELP

Long story short - I've bought a Y61 patrol from a dealership, found out only after I got it home that it's had an engine conversion from an RD28 to a Y60 TD42. It's been turbo'd and mod plated.
It was doing 4000rpm @ 100kph so the rear diff was changed from 4.6 ratio t a 4.1 and now it's doing 3800rpm @ 100kph
I still think that it's way too high, it sounds terrible. I do a lot of highway driving and live out west so I need to get this sorted asap.

It's a 5 speed manual, the clutch isn't slipping and it currently has 31s

If anyone has any idea what's going on please let me know, I'm at an absolute loss as what to look at now.

Bump for @jesskac92 due 2 this thread going into moderation

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Originally Posted by NissanGQ4.2

Bump for @jesskac92 due 2 this thread going into moderation

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This is way left field but if it has had an engine swap, was the gearbox swapped as well? Maybe the gearbox ratios are wrong for the motor. Just a thought I have no experience in this.


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Bit of a long shot but is the speedo and tacho reading right?
3800 at 100 sounds massivly high

Gearboxes are different on RD28 to TD42, RD28 too small and wont fit. Transfer case ratios are the same.

Jess,

Not even sure that the old 4.2 in standard form liked 4000rpm .... anything past 3500rpm was a waste of time ....

Even accounting for the Diff Ratios with the engine change, it doesn't seem right and it seems like the Tacho is way out, and you may need a different adapter gear.

The 4.2 runs a different gearbox to the 2.8, so it is likely that the tacho is giving you the wrong reading.

Pretty sure mine was somewhere around 2200 - 2400rpm at 100, but it was 17 years ago that I had mine, so someone with current info will confirm.


PS I hope you changed front and rear ratios at the same time, as you can't run different ratios front and back in 4wd.

I have changed front and rear ratios, yes :)

I'm waiting on a tacho reader, we live in the middle of nowhere so eBay is my friend.

I'd like to think the tacho is wrong but it really doesn't sound like it, it's really singing at 100kph.

maybe give Reidies earth moving in Bendigo a ring for some info
May have to google his phone number

Is this your first td42?

Reason I ask that is our work car td42 with a straight through exhaust sounds like your pinging it when you're only at 2400 rpm.

Sounds a bit strange but you could get someone to video or do sound video when you're driving at 100km and throw it up here for members to look at maybe.


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33's 4.1 diffs with a td42 and i sit on 100 at 2200rpm. it is a gq but i think it would be the same. hmm i think maybe tacho not reading correct ? other wise is it in low range ? ..