Ive fully restored my 84 hilux from groundup and replaced the old 2 litre petrol engine with a 3.8 holden motor. It runs great with no problems whatsoever, but, even with a 5 speed box it feels if it needs another top speed gear. Would a senator 6 speed be better or perhaps change the diff ? cheers.
skull,
Jan 21, 3:37pm
Look into changing the diff ratio, the final gear in the gearbox on a 6 speed won't be a whole heap different to a 5 speed. The extra gear is used to decrease the differences in the lower gears not usually an extra big dollop on top gear.
msigg,
Jan 21, 3:43pm
Yes you can change the diff ratio, seen this done with the v8 drivi g it and was too low in 5th.
kazbanz,
Jan 21, 4:30pm
My thinking is that you need more specifics before diving in and changing anything. Your "bummometer" might be way out or worse you could end up going too far the other way and having something that crawls off the line. So I'd be hooking up a rev counter and taking a few notes. 100 km/h gear 5 3500rpm 50 km/h Gear 1 4000 rpm- for example. Then you will know by how much you need to change the diff ratio to drop the rpm at the different speeds.
tygertung,
Jan 21, 5:01pm
Will you need to change the front and the back differential so the front and back wheels don't want to be doing different speeds?
gph1961,
Jan 21, 5:11pm
who said it is 4WD?
bwg11,
Jan 21, 5:17pm
I'm assuming it is a 2WD Hilux otherwise it gets complicated. Check the top gear ratios of the 5 and 6 speeders you mention, I guess they will both have "overdriven" top gears and it is possible the 6 speeder may be the same or lower than the 5 speeder, so check the ratios first. I bought a 18R Hilux new and remember it as quite low geared on the open road. Mine was 4 on the column. With the V6 Holden, you need to be looking a gearing that gives you something like 2000 rpm at 100kph. I doubt an "overdrive" top gear, of say, 0.85, would give this with the stock diff. Find out your actual ratios, measure your tyres and get your calculator out (or use one of the on-line speed/rpm calculators). Your engine swap should make a pleasant drive.
franc123,
Jan 21, 5:58pm
I would just go with a diff change. I've seen this exact V6 Holden conversion done before on one of those and it made an excellent truck out of it, with little difference in fuel economy for much better open road performance. I can't recall how the gearing was dealt with, it was a VP engine with the TH700 auto hence having a 0.7:1 OD ratio but some other higher diff head was fitted to it, might have been out of a Cressida or MkII or something similar. He was able to get down close to what the Commodore was, something like 2200-2300rpm @100kph, having it slightly shorter was an advantage when carrying heavy loads.
tweake,
Jan 21, 6:30pm
what gearbox is it running? there is a bit of difference in gearing between the models (assuming toyota box). eg some have lower 1st gear. the problem with changing the diff is first gear tends to suck.
tons of factory and aftermarket diff ratios for toyota 8"diffs.
thedevil1,
Jan 24, 9:43am
Thanks everyone. Its a standard 2wd ute. Flatdeck with V6 3.8 bolted up to original 5speed box with adapter. Sitting on original 14 inch wheels. Because the original 2 litre petrol motor had hit nearly 500k, I took the opportunity of replacing it with the holden motor I had sitting in the shed. Its my retirement project and Im chuffed how it came out. The ute is exactly like it came out of the factory, no lowered suspension or anything. A very cruisy ride with more power on the hills carrying a load. My son tested it, and its sitting on just over 2300 @ 100k. He suggested switching wheels to 15 or 16 inch (falcon wheels) and it more of a matter getting used to the different engine sound and perhaps use a different muffler exhaust system than the original tinny one. Cheers everyone.
tweake,
Jan 24, 9:59am
the factory exhaust will be strangling the engine. the gearbox and diff (most likely the 2 pinion diff) are the weak point in the drive line especially with 500k on it. the drive line from the 3 litre v6 models is a good upgrade. (r150 box and 4 pinion diff)
mrfxit,
Jan 24, 10:58am
Oh dear, I sense other issues popping up if not careful. OEM 2ltr gear box behind a 3.8 v6 OEM 2ltr diff on a 3.8 v6 OEM 2ltr exhaust on a 3.8 v6 OEM 2ltr engine /front shocks holding up a 3.8 v6 Oh & . OEM 2ltr front brakes . . . . . & speedo calibration will be a problem once you fix the other issues.
Yea I think that about sums it up
Brilliant swap, but theres a "few" issues for long life & certification (& thats just the logical issues for cert)
mrfxit,
Sep 23, 7:47pm
Been there done similar but different brands. Big 6 engine on small/ medium 4cyl gear will give problems & thats without giving it a hiding (heavy foot/ heavy loads etc)
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