2.5" or 3" exhaust on 4bd1 T

**Bush65** · 16th August 2006, 05:50 PM

Originally Posted by Larns

Def90
It's definatly worth it, I've converted a couple (including my own ) to 3" and the dyno dosn't lie! Go the full flow system.

Dranged
I'm looking into the R380 conversion to go behind my 4bd1-T, a couple of Q's if you have time. What high range ratio are you running in the 230? and what sort of fuel consuption dose your rig get? I've heard good reports about the conversion, what's your thoughts?

TIA

Cheers Larns

The 4BD1 and 4BD1-T are hard on gearboxes because the high torque at low revs results in high torque impulses.

R380 stands for Rover transmission and the torque rating of 380 Nm. Which is not high for behind the 4BD1-T.

There are 3 variations of R380 - suffix J, K and L (a suffix in the serial number).

When introduced in 1994 to replace the LT77, the suffix J had an extra bearing on the main and lay shafts extension for 5th and reverse, wider gears, larger dia syncro rings and steel oil pump.

The suffix J has a bad reputation for breaking the extension of the mainshaft at a bad stress raiser.

This was fixed when the suffix K was introduced in 99.

The suffix K was soon replaced by the suffix L, which is still current.

The suffix L is much stronger than the suffix J. Some of the bearings were uprated and some gears are wider/stronger.

If you must have an R380 behind a 4BD1, try to get a suffix L unit.

**Larns** · 16th August 2006, 05:57 PM

Thanks John that's pretty interesting. I have been told that with the R380 conversion not to engage 5th untill you hit 90km/h, that way you reduce the total amount of tortional vibration through 5th. Brad in Brissy, that dose the conversions, seems to think that the R380 is no weaker than the LT-85(an easier to get parts for). He has one of these conversions behind his turboed Isuzu an hes done well over 150k with it and claims it's had no dramas. Am interested to see what Dranged has to say about them.

Cheers

**DRanged** · 16th August 2006, 08:57 PM

Gday Larns

I have had the R380 now for 2 years behind the Isuzu with no problems. As I only use the car for off road mainly, milage is unknown but it has done 350hours.
Not changing into 5th untill 90km/h ? I think not. I run the tallest high range gearing you can put in an LT230 and run 33" tyres and if I waited till 90 to change, your reving the engine a little hard.
Its all about the way you treat your vehicle in terms of reliability. Its not a race car so dont drive it like one. Of coarse you try not to subject the gearbox to huge amounts of torque ,but we are talking 4BD1,s here and basically thats what they produce.
I run synthetic ATF fluid in my g/box and transfer case with great success and to date no problems. I will be pulling the g/box out soon to relap 4th & 5th as they have been whinning since we built the box, so I will check out the wear and stress if any. If your ever in the Tweed Heads area come and take it for a spin! The only problem I had converting it was tracking down a LT85 bellhousing which we modified to suit the R380. As for consumption ??? I dont worry about that, all I have to compare is I towed a 2t camper to Rover Park and back and spent 2 full days hard 4wding probably 650-700km used 80-90lt???. Anyway who cares its a great package off road which is the only place i break things, mostly stub shafts and rear tail shafts.

Regards Justin
PS Do you know that after a nuclear holocauste only 2 things can servive?

Cockroaches and 3.9 Isuzu,s

**Larns** · 16th August 2006, 10:10 PM

Justin
Sounds like they are the go then. I've already sourced the required bellhousing for the conversion, was just saving for the conversion, who did your conversion? an how much?
I've got a 230 from behind an auto with the 1:1 ratio(hard to find I've been told) so this sould give me crusing speed even when towing in fourth.
Just out of curiosity what suffix are you runnig in your truck? Was it a factor in the conversion. I only ask because I've bought two R380 with the intention of making one good one out of them, and they are both this "J" suffix, or can you simply add the stronger suffix "L" parts whilst rebuilding?

Cheers Larns

**DRanged** · 17th August 2006, 07:40 PM

Larns

We did the conversion ourselves but I have a good mate in sydney with a jig to modify your bellhousing if required. I will have a look at the prefix of the box tomorrow, but it was not a factor when building it. When the car is off road or on road it works hard but is driven gently, consiquently no gearbox problems. It runs 33" muds with maxidrive rock crawlers in the LT230 and front and rear maxi drive lockers and is used for very hard terrain most of the time.

Regards Justin

**Larns** · 17th August 2006, 09:34 PM

Justin
cheers mate PM sent

**StuRR80** · 22nd August 2006, 12:40 PM

If you're looking for some hints and tips on isuzu engines, try www.clubisuzu.com, especially for the 4BD1T's.

Cheers,

**Rosco** · 22nd August 2006, 02:02 PM

Originally Posted by def-90

it also will depend upon if i can get my dump pipe enlarged as well? it's pretty tight .......

Oooooooo .. now doesn't that make your eyes water at the very thought

...........

Thread: 2.5" or 3" exhaust on 4bd1 T

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