12h-t Sucks Off-road??

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

D

dogboy2

Joined
Jul 8, 2004
Threads
41
Messages
996
Location
Portland, OR
Forgive me, I'm a complete diesel newbie (but learning more each day) and in searching this forum for info on the 12H-T, I've come across a few posts that claim this particular diesel motor is awful to drive off-road. Although I waded through 9 pages of threads on this engine, I wasn't able to get a clear understanding of why this may be so.

Would someone be so kind as to help educate me on this issue? I'm seriously considering following Mountain Goat's conversion path with my '87 FJ-60 and despite the 2F's shortcomings, I've been very pleased with it's performance off-road.

Not anxious to spend a bunch of $$$$ on a motor conversion to only trade shortcomings in the end. From everything I've been able to gather, the 12H-T sounds like the ideal diesel to drop into this rig.

Thanks in advance for your input,
-dogboy- '87 FJ60
 
The 12HT is a great engine offroad and I dont think anyone who has driven one would disagree.
However,the throttle on manual transmissions makes it very difficult to maintain a steady rate of power as the the bumps cause your foot to bounce which cause the vehicle to lurch forward and make it even harder to keep a steady rate of progress.
I think Greg B has a fix:)
I havent driven the auto but it is apparently more manageable.

Dont let it turn you off as you can get use to it and if you had a hand throttle fitted that would also negate the problem
 
roscoFJ73 said:
The 12HT is a great engine offroad and I dont think anyone who has driven one would disagree.
However,the throttle on manual transmissions makes it very difficult to maintain a steady rate of power as the the bumps cause your foot to bounce which cause the vehicle to lurch forward and make it even harder to keep a steady rate of progress.
I think Greg B has a fix:)
I havent driven the auto but it is apparently more manageable.

Dont let it turn you off as you can get use to it and if you had a hand throttle fitted that would also negate the problem
Click to expand...

Thanks Rosco... doesn't sound like the accidental throttle bumping is really any more of an issue than it is with the 2F. Can't tell you how many times I've done this when things get bumpy.

One nice thing about the 2F is that it can crawl along at idle speed (terrain depending) without having to place your foot on the pedal -- is the 12H-T any different?

-dogboy- '87 FJ60
 
I've bounced off the roof more times than I'd like to admit. Never a throttle issue. That's 2f and the hz-t plants. I actually think my HZ is incredible offroad. The low end grunt-when wanted, no downhill braking (H55) when in proper gear, no drowning while sitting window deep waiting for help. I'm not too sure a 12ht would be a whole lot different, especially with the low range gears that offer instant action. Heck, I'd have to push it off on driver issues, not power plant issues. Bob
 
roscoFJ73 said:
The 12HT is a great engine offroad and I dont think anyone who has driven one would disagree.
However,the throttle on manual transmissions makes it very difficult to maintain a steady rate of power as the the bumps cause your foot to bounce which cause the vehicle to lurch forward and make it even harder to keep a steady rate of progress.
I think Greg B has a fix:)
I havent driven the auto but it is apparently more manageable.

Dont let it turn you off as you can get use to it and if you had a hand throttle fitted that would also negate the problem
Click to expand...

X2, The 12HT throttle is a lot more touchy than your 2F or a 2H the way it is set up.A lot of it can be corrected , a small draw back for nearly double the fuel economy off road, less maintenance,better reliability and driveability etc.cheers
 
dogboy2 said:
Thanks Rosco... doesn't sound like the accidental throttle bumping is really any more of an issue than it is with the 2F. Can't tell you how many times I've done this when things get bumpy.

One nice thing about the 2F is that it can crawl along at idle speed (terrain depending) without having to place your foot on the pedal -- is the 12H-T any different?

-dogboy- '87 FJ60
Click to expand...
I have 2X 1HZs and I also had 3F in the FJ73 and I also had a HJ61 for a short while and believe me there is a big difference in sensitivity with the 12HT:D
The 12HT can crawl along with the best but when you need to blip the throttle on rough ground it gets more blip than you want ;)

Thats why I was hoping Greg B would come along as I never really got to investigate why.
 
if the only issue is that the throttle is too touchy, why not extend the throttle arm moving where the throttle cable connects outwards. This would decrease sensitivity although it may stop you from getting full throttle.

Maybe you would have to increase the range of motion for the gas pedal as well.
 
cody c said:
if the only issue is that the throttle is too touchy, why not extend the throttle arm moving where the throttle cable connects outwards. This would decrease sensitivity although it may stop you from getting full throttle.

Maybe you would have to increase the range of motion for the gas pedal as well.
Click to expand...

Maybe but you would have to be careful not to limt the throttle travel.
Another way maybe to try some different springs.
 
roscoFJ73 said:
Thats why I was hoping Greg B would come along as I never really got to investigate why.
Click to expand...

Three potential fixes I've heard about but never investigated myself...

1) There is space on the return linkage at the injection pump for a second spring.

2) Move the pivot point behind the pedal to a higher spot on the pedal.

3) Place a shock behind the fuel pedal ala some high end European cars.

And do not drive with your foot in the air. Support your foot as best you can: (tranny tunnel in LHD, or drivers kickpanel in RHD).

hth's

gb
 
Thanks Greg, that does help. :)

So with a little re-engineering and some saddle time with the "new" motor, it's sounds as though with a bit of practice this isn't really an issue at all but rather one of driving technique.

-dogboy- '87 FJ60
 
bigbrowndog said:
X2, The 12HT....nearly double the fuel economy off road, less maintenance,better reliability and driveability etc.cheers
Click to expand...

I like the sounds of all this... a lot :D

Less maintenance? Better reliability? How does the 12H-T differ in these regards as compared to the 2F?

-dogboy- '87 FJ60
 
dont sweat it dogboy,i found mine a bit touchy when i first got it but after a few weeks you adjust.
cheers goldchaser
 
oh just seen your last post dogboy,i had a 60 series 3f before the 12ht,big difference in power,3f would die on hills,12ht just keeps pulling,i wouldnt compare them too much.
cheers goldchaser
 
The hand throttle works great in those lower speed situations. I have the m/t 12 ht combo and they are all right the throttle is touchy at low RPM but if you install a hand throttle all is well.
Allows me to use the clutch and brake without having to switch over to the gas pedal as well.


No BOUNCY BOUNCY:bounce: :bounce2:
 
In the short time that I've owned a 12H-T I've found it unstopable off road. The torque well exceeds traction (open diffs).

I have also experienced the throttle issue. I added another spring and it didn't fix the problem, but maybe it wasn't heavy enough.

Love the engine though. I'll never go back.
 
Mountain Goat said:
In the short time that I've owned a 12H-T I've found it unstopable off road. The torque well exceeds traction (open diffs).

I have also experienced the throttle issue. I added another spring and it didn't fix the problem, but maybe it wasn't heavy enough.

Love the engine though. I'll never go back.
Click to expand...

Oh yes, don't I know it, deliverer of my destruction....ruined for life I am, ruined for life.....

Until I find the right deal on a good 12H-T that is!! MUUHAHAHAHAHAHAHAHAHAHA!!!!

-db-
 
Yeah, I posted on your thread before I realized who the owner is.

If you want confirmation of off-road performance, we should take it out some time soon.

How's the search going? You mentioned you have a couple of leads.

:cheers: Good luck, my friend!
 
Greg_B said:
And do not drive with your foot in the air. Support your foot as best you can: (tranny tunnel in LHD, or drivers kickpanel in RHD).
Click to expand...

pretty easy to me .. and I never be in this issue .. in my 2H-T
 
You must log in or register to reply here.

Share this page

Back
Top Bottom