Hydra lost gears

[Aussy Edo]

Dudes,
Got within 150m of home last night and the car lost Drive and started making a whirrrrrrring sound. I pulled over and turned it off.
The hydra gear box locks the wheels when in Park like it should but in all other gears it free wheels like it is in Neutral.
The fluid looks ok although i havent drained it yet, was just going off the dipstick.
Havent had an issue with the Hydra since i have had the car so am unfamiliar with the set up.
Sounds like a selector of some sort may have snapped inside the box but why would it still be whirring in Park and Neutral?
I can probably take a video of the sound its making if that would help to diagnose the issue
Thoughts please Gearbox Gurus!!
Edo

[Harv]

Edo,

I'm no hydra expert (it's on the list of things to do... couple of boxes under the house and nearly a full set of GMH service tools, just need the time), though the GMH hydra workshop manual suggests the following:
a) low oil level (needs to be checked in Park with the engine running... I learnt that one the dumbarse way when I owned my first traumatic).
b) low oil pressure (mostly a tear-down job, unless the filter is blocked - filter change is a DIY task).
c) incorrectly adjusted shift linkage (not likely in your case as you had it running, but a DIY check with only a feeler gauge needed).
d) band adjustment (can be a DIY job if you have a torque wrench that can adjust down to 100 inchpounds... not footpounds!).
e) band servo not applying (tear-down job).
f) coupling exhaust valves stuck open (tear-down job).
g) Blocked oil passage (coupling feed or band apply - tear-down job).
h) Governor primary or secondary valves stuck open causing the 2-3 shift valve train to assume its third ratio position (tear-down job).

Cheers,
Harv

[Aussy Edo]

Thanks Harv, will hopefully get to have a look over the next few weeks, just glad it happened close to home.
Are the filters hard to get to?
I have usually just kept the fluid up to it as it only gets driven approx once a month on short trips.
I dont like my chances of getting it rebuilt in the town i am in at the moment.
might try and get my hands on another one.
Is it easier to pull motor and box out at once or can you do the box just from underneath the car?
would be easier bolting it to the engine when it is out of the car?
Edo

[Harv]

Filter is easy enough to get to - drain the oil, drop the pan, and the filter is sitting right at the bottom of the transmission. New filter, new pan gasket, new oil and done. Quick job to tighten the band whilst you are there (need that small torque wrench though).

Never pulled a hydra, but assume it's like a crashie - if its out of the car already, connect it to the motor to install. If it's in the car, separate box and motor and only remove gearbox.

Cheers,
Harv

[Aussy Edo]

Hey Harv,
How do i tighten the band mate?
Got any photos of the process , i dont have a manual for the car.
Cheerz
Edo

[Harv]

Edo,

You tighten it similar to this:



Note that the photo shows them tightening the band with the box on a bench - you will be working upside down relative to this. The HM-8591 tool is not critical, but the inch-pound torque wrench is.

Cheers,
Harv

[Aussy Edo]

Thanks mate, was speaking to a guy the other day about it, he thinks it could be the spline on the damper plate being stripped.
Will have to investigate over the holidays.
Edo

[feats EK]

Hi,
What was the washup of this problem ????

Regards


Feats

[Errol62]

This may sound silly but would one foot lb be about 12 inch lbs? So 100 inch lbs = 8.33333333333333333333333333333333333 ft lbs. round about ish?

[Harv]

Correct. 1 ftlb = 12inchlb. Be cautious using the bottom end of a ftlb torque wrench to tighten inchlb settings... when you are down at the 0-10 ftlb range, the ftlb torque wrenches are none too accurate.

Cheers,
Harv