HZJ77 O/D Off light flashing?

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Loomin

Loomin

10 Year
Joined
Jan 26, 2016
Threads
6
Messages
80
Location
Vancouver, Canada
Hey guys, I have a problem. On my 93 HZJ77 the "O/D off" light is flashing indicating a transmission fault. I did bunch of searching and tried the paperclip diagnostic method but i am not getting any lights flashing codes or anything. My gauge cluster doesn't even have a check engine light! the OD off light just flashes steadily. Its got a 1HZ and its auto. I got the truck with this condition already present so i am not really sure how its supposed to shift but it goes through the gears really quickly and never seems to reach the power band of the engine. Merging onto the highway is embarrassing on a good day. It usually shifts before 2000 rpm even when i mash the gas pedal. If i am cruising and need to get up a hill, i try to floor it expecting it to downshift but it does not. I have tightened the throttle cable too but no luck.

Any ideas?
 
cool ill try that.

Just took it on a long ish road trip over the weekend. its painfully slow. max speed on flat is only 108kmh. Blows coal like a steam engine on anything over 50% throttle. i get passed by semis going up hills. is that normal? This is my first 1hz so im not sure what to expect.
 
No not normal. Before turbo I could easily get to 130 kmp/h if I desired and if I had enough runway to build speed. BJ74s with turbos could not keep up to my NA 1HZ. Hills were brutal though and I never had the slightest puff of smoke. On the Coq id be doing 80kmp/h up the hills but now that I'm turbod it's a much different story. Fwiw I have a manual 5 speed
 
Loomin said:
cool ill try that.

Just took it on a long ish road trip over the weekend. its painfully slow. max speed on flat is only 108kmh. Blows coal like a steam engine on anything over 50% throttle. i get passed by semis going up hills. is that normal? This is my first 1hz so im not sure what to expect.
Click to expand...
Although I've only driven my HZJ77 for a couple of months here's my observation:
(88,000 kms, auto, no turbo)
IT NEEDS A TURBO in the worse way.
Unless you "force the issue" the 1HZ struggles to hold speed even on mild inclines. In my case
(again it's my first 1HZ) if you force the transmission to downshift to hold speed, the EGT's will rapidly move into the 1,000-1,100 degree range. I'm hoping a turbo and Intercooler will solve the problem.
Sent from my iPad
 
The 1hz has around 130 HP you guys need to get those transmissions serviced as they should kick down and power through the hills. Do you guys have any problems if you hold each gear when driving.
 
1hz auto. If you need any more info from the manual just ask.
1hz auto 001.webp
1hz auto 002.webp
1hz auto 003.webp
 
ozcrusier said:
The 1hz has around 130 HP you guys need to get those transmissions serviced as they should kick down and power through the hills. Do you guys have any problems if you hold each gear when driving.
Click to expand...
In my case, the transmission is working as it's designed however downshifting isn't always an option depending on speed. Time will tell but I believe the engine will come alive with a tuned turbo and Intercooler. My 2H was similarilly lethargic until 10psi of boost was introduced. :)
 
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You mentioned that it's blowing a lot of smoke. The PO might've turned up the fuel trying to get more power. Make sure your fuel delivery system is as it should before you go too far. From there you can start going into the transmission.
 
Yeah it smokes like crazy especially on the highway trying to hold 100kmh i have to really give it all shes got. i got a pyrometer just now and i'm going to install it to try to tune by EGT.

Thanks for posting those service manual pages! I'm going to make sure everything is within spec.

The problem i am having is that it just goes through the gears so quickly that it never really has time to reach the powerband of the engine. perhaps i will make a video
 
No sorry
I have most others but not the RM188E transmission manual. The repair manualS I have covers the transmission quite well but it's for the A440F.

A440F 001.webp
 
Just tried to measure an adjust the throttle cable as mentioned. There are no stoppers to measure.

I am going to drop the tranny pan and clean the filter etc. I think its overdue. :worms:
 
These engines are extremely expensive to do major repairs on. If it were me I'd remove your IP and send it to Jon Fox at Okanagan Diesel Injection in Vernon. He can test it and set it up to spec so theres no need to bother with EGT and pyro until/if you decide turbo. It cost me $150 or so to do mine. It's not worth melting holes in your pistons IMO. I tried doing it with the gauge and thought I did an okay job knowing it wasnt perfect. Turned out it was waaay out and way over fueling.

Can't comment too much on your transmission as I've never owned an automatic before but an extreme valve body might help out too, or a H55F swap...
 
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