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Discussion Starter · #1 ·
My first post here! Nice to see an active forum.

I have a 97 disco with an odd tranny shifting issue. Cold startup I can drive away no problems....however, if I shut the truck down when the tranny is warmed up/hot, it does not want to upshift properly when I start back up.It hangs in 3rd...when slowing down, it downshifts somewhat abruptly. It only does this when hot...

I was told by a non Rover mech that there is a pump inside the tranny that if not working properly ...will not generate the needed pressure to get the clutch packs to engage properly.
I know this tranny is not controlled by the ECU so that has been ruled out.
My next step is to dump the tranny fluid and get a fresh filter..

Aside from
the pump theory,,,anyone have any ideas? I love my Disco and dont want to get ride of her. I suppose I could swap the tranny on her but if there is something simple hiding from me...that would be best...lol

Thanks
 

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Discussion Starter · #3 ·
looks like the Valve control body was not functioning properly....Options...have it yanked and dissasembled/repaired/cleaned...$600+ or Yank the old one out and find a replacement unit.??$$

I chose option 2...rebuilt valve body $99usd plus $25 core charge, new filter and gasket $17....the amount of knuckle busting and cursing....Priceless!

Things to contend with if you choose this option. Sourceing a valve body...I went with hardParts for transmissions out of NJ. Flo was the shite and put up with all my crazy questions...and shipped it COD...!!

1st You must disconnect the exhaust from the manifold so the cat converters can be lowered to make clearance for the cross brace lowering so you can get the trans pan out...follow that?? lol

Unbolt the valve body....good luck figuring out which one of the 30 torx screws hold the valve body to the trans vs holding the halves of the valve body together...they all look more or less the same. The difference after the fact??? the heads are slightly larger on the mounting screws although it takes the same torx bit for all of them.

Now...the replacement unit did not come with the paper gasket in between the halves of the unit....so......I dissasemble the old one to get the gasket out and decide if I shoule even consider installing it into the new one. Answer?????? HELL NO! the inside is a crazy maxe of worm channels,check balls, springs, etc... that would make Einstien wince in pain!
$70 to have a PROFESSIONAL install the gasket.. :buttrock:

anyway....all bolted up except for the drivers side exhaust...all three studs snapped off during dissasembly and now I have to extract them to bolt her back up. :mad: :mad: :mad: :mad: I should have her together tomorrow and road test it...wish me luck!


bottom line....it really wasn't too complicated but it took some time. If you ever have to replace a valve body and you dont mind getting your hands dirty...dig in, it aint really that bad...just time consuming.... plus it was alot cheaper...$211 vs $600...or more..
 

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Discussion Starter · #5 ·
Ok...official road test today and.....no difference in the transmission. The initial problem is still there!!!!

Wil not upshift into 4th (hangs in 3rd)unless its cold. As it gets hot, it then begins to hang in 2nd. In both cases I can slide the gearbox into Neutral and pump the accelerator and drop back into Drive to prompt the upshift, but as soon as I come to a neutral throttle position or let off the accellerator, it will abruptly downshift back into 3rd, or 2nd .


Is there some type of TPS or electronic modulation of input to the transmission. Or could the transmission oil pump be bad...(hence the revving to build pressure prompts the upshift) Only other item in the gearbox that regulates fluid pressure is the oil pump...???


Hell...I think I'll just get one from a breaker...
 

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Discussion Starter · #7 ·
Ok...the thread that wont die...LOL

I have a second vehicle that I drive most days so I've been driving this truck with the same issue for 3 years...LOL

Winter mostly so out to my hunting spot....the trans cools off and I drive it home.

FFWD to now....Its completely irritating and I love my disco so I'm not getting rid of it. Now...to fix the problem once and for all.
Its "new" transmission time.

Its a 97 series I......the question is do I have to use a ZF4HP22 (seriesI)or will a ZF4HP24 (SeriesII) work also?

Is the 24 an electronic Valve body?
 

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Stock '96 Discovery
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Hey do you guys know if you can replace a "parking pawl" or "parking pin" on a tranny? Before I bought my disco, someone towed it while it was in park and broke it, therefore it doesn't hold in park. :complain: I have to use the e-brake like if it was a stick shift.
From what I have researched, this pin lodges in notches on the wall of the tranny.

More information...

next item that regulates the pressure...and is easy to get to...the Governor. I have also decided to get a gearbox Tech manual for the ZF4HP22 unit. Got it from Axiom Welcome To Axiom Online for a bout $15.00 shipped...not bad

I'll keep the board informed
 
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