Reflections on 4BD1T vs 300TDi

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Originally Posted by C H T

uninformed

<SNIP> I didn't use an Isuzu box because there were no easy options as to fitting one, and I already had the late suffix R380. I have looked at the MYY6S because the ratios would work very well but cost is a factor, and I'm not sure whether TheGrubbs conversion kit would suit the late model box

FWIW

C H T

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Hey CHT,

I did look at the MYY6S. The box is totally different to the MSA series. The MSA adaptor kit I can confirm definitely won't fit.

There would be a few challenges with fitting the MYY6S. Namely the bellhousing size is larger and the clutch slave ends up where the 4BD1 starter motor is and you can't use the rear facing MYY6S starter motor position as there is the firewall in the way.

What would be interesting is the AMT version of the box.

With no dry clutch would solve the slave cylinder problem and being electronically controlled means no shiftery bits would need to be designed. Just mount the electronic shifter where ever. Then only a rear adaptor/shaft would be required (with a bellhousing fix/adaptor). It would however mean some electrics would need to be added which kind of starts getting away from the simplicity of the 4BD1's purpose. Perhaps better solution than an auto however and claimed benefits of extended clutch life and drive line smoothness.

http://www.isuzutruckssa.com/isuzu/action/media/downloadFile'media_fileid=797

Oh and my 2 cents on gear ratios :)

A MSA-5G with a 1.003 LT230 compared to a R380 with a 1.22 LT230 ends up with final gearbox/transfer case ratio's of;

3rd basically the same between both (1.59 to 1.56)

Then with a wider spread over all the other gears with the MSA.

FTTAI more info on the Isuzu AMT

ISUZU:Engineering the "Smoother-E Autoshift"

TheGrubb

Thankyou for the info - when I looked at the MYY6S it seemed to me tha tthe best way to fit one would be to replace the bellhousing and therefore resolve the starter motor/slave cylinder problem. I would still give consideration to fitting an Isuzu six speed, but at present the set that i am using is working and lasting very well. The electronically controlled box is not of interest because, as you say, it gets away from the inherent symplicity of the 4BD1.

C H T

Quote:

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Originally Posted by C H T

TheGrubb

Thankyou for the info - when I looked at the MYY6S it seemed to me tha tthe best way to fit one would be to replace the bellhousing and therefore resolve the starter motor/slave cylinder problem. I would still give consideration to fitting an Isuzu six speed, but at present the set that i am using is working and lasting very well. The electronically controlled box is not of interest because, as you say, it gets away from the inherent symplicity of the 4BD1.

C H T

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I had to change the bellhousing of my 6 speed MXA box to bolt up to the 4BD1T.

The bellhousing I used needed a small machining alteration because the centre distance between main and lay shafts was greater in the MXA. The bearings protrude a small distance from the gear case and act as location for the bellhousing. We used a milling machine to cut the recess for the layshaft bearing on the new centres - I was not concerned that the altered recess was oval shape and did not locate over its full perimeter, because the other bearing and the dowel pins provide satisfactory location.

I was fortunate that the mounting bolts were in the same location in the MXA and no other mods were required.

I haven't had anything to do with any later Isuzu boxes, so don't know of other possible issues.