ZFHP22 in Classic Range Rover, downshift problem in summer

[93 4.2 LWB RR]

My 1993 Range Rover acts up in the summer time when I approach a stop. As the transmission slides from 2nd into 1st gear, I hear a "clunk". I don't notice any sound if the engine is cold. Anyone have a similar experience, and be able to share what the fix was?

Thank you.
Mike

[DaveEFI]

My 1993 Range Rover acts up in the summer time when I approach a stop. As the transmission slides from 2nd into 1st gear, I hear a "clunk". I don't notice any sound if the engine is cold. Anyone have a similar experience, and be able to share what the fix was?

Thank you.
Mike

On a purely cable controlled box (early 4HP22 were and ones like the B-W 35 and 65) it's usually the line pressure too high caused by the cable being too 'tight'. Many adjust these to get the kickdown working when it's actually the throttle travel which needs adjusting - slack in that prevents full throttle.
Later 4 HP22 used a different type of control, IIRC.

[93 4.2 LWB RR]

Thanks for the help Dave. I'm a novice, so please bear with me. The problem occurs when I'm downshifting and not applying anything to the throttle. Are you suggesting that the base idle speed if off?

Thank you.
Mike

[DaveEFI]

Thanks for the help Dave. I'm a novice, so please bear with me. The problem occurs when I'm downshifting and not applying anything to the throttle. Are you suggesting that the base idle speed if off?

Thank you.
Mike

The effect you're describing is called the roll out 2-1 shift. If the line pressure is too high at idle, you'll get a rough shift.
Normal idle speeds - even with the engine cold - shouldn't cause this. However, if the idle speed has been increased in the wrong way by opening the actual throttle, it might well cause it. As I said, the relationship between the throttle mechanism and box shift cable is crucial to correct operation.

[93 4.2 LWB RR]

Dave,

Adjusted the tension on the idle, and now I notice that there is some "clunk" (less noticable but the same kind of sound) on the upshift. The more time I spend paying attention to the sounds of this truck, the more I hear. The mechanic that spent some time on it thinks it is stretch in the drive chain, and that I needn't worry about it. I tend to agree with him. What do you think?

Mike

[kiwicar]

Hi
The clunking can be due to worn radius arm bushings that attach the axles to the chassis.
Best regards
Mike

[ChrisJC]

Or the top balljoint on the rear axle.

Chris.

[DaveEFI]

Dave,

Adjusted the tension on the idle, and now I notice that there is some "clunk" (less noticable but the same kind of sound) on the upshift. The more time I spend paying attention to the sounds of this truck, the more I hear. The mechanic that spent some time on it thinks it is stretch in the drive chain, and that I needn't worry about it. I tend to agree with him. What do you think?

Mike

Try disconnecting the gearbox control cable completely. Then go for a gentle short drive. If the roll out 2-1 shift is now smooth you have your answer. Do NOT leave it like this or drive hard on the test journey as you could damage the 'box.
If the roll out shift down is now smooth, the entire accelerator pedal to throttle linkage needs checking for wear, repairing if necessary and adjusting as per the book. Only then can the gearbox control cable be set correctly.
Sadly, most mechanics have little clue to checking/adjusting auto boxes.

Slack in the drive train etc shouldn't cause a rough roll out change as a correctly set gearbox is free-wheeling under these conditions.

[93 4.2 LWB RR]

Dave, Mike and Chris,

Thanks greatly for the feedback on my "clonk". After driving it for awhile, and using your ideas to tune my ear in, I'm fairly certain that the issue is between the accelerator linkage and the kickdown linkage. As the change in the throttle position changed the nature of the "clonk" (for the better), I'm going to drive it awhile before I make any other investations. I'll eventually disconnect the kickdown linkage to test the accelerator linkage as Dave suggests, but only when I'm confident I know what driving "gently" means. Right now it aint broke, so I aint gonna fix it.

Cheers mates,
Mike

[93 4.2 LWB RR]

Alright, I came to terms with disconnecting the gearbox cable, and took a gentle drive once around the block. On the 1-10 clonk scale (10=walk into a closed door) it was a 6 on the first 2-1 downshift, much worse than when it was connected.

I looked at the radius arm bushings, and they look good. Can't get a good look at the rear axle ball joint, but I don't know if I could see a problem with this if I had a good look.

Thanks again for the help.

Mike

[DaveEFI]

Alright, I came to terms with disconnecting the gearbox cable, and took a gentle drive once around the block. On the 1-10 clonk scale (10=walk into a closed door) it was a 6 on the first 2-1 downshift, much worse than when it was connected.

I looked at the radius arm bushings, and they look good. Can't get a good look at the rear axle ball joint, but I don't know if I could see a problem with this if I had a good look.

Thanks again for the help.

Mike

Right. That doesn't make sense. Only think I can think of is the spring biasing that tends to close the valve is broken or jammed - and the cable is sort of pushing it closed when connected.

[DaveEFI]

Alright, I came to terms with disconnecting the gearbox cable, and took a gentle drive once around the block. On the 1-10 clonk scale (10=walk into a closed door) it was a 6 on the first 2-1 downshift, much worse than when it was connected.

I looked at the radius arm bushings, and they look good. Can't get a good look at the rear axle ball joint, but I don't know if I could see a problem with this if I had a good look.

Thanks again for the help.

Mike

Right. That doesn't make sense. Only think I can think of is the spring biasing that tends to close the valve is broken or jammed - and the cable is sort of pushing it closed when connected.

[Eliot]

The reason he says drive gentle presumably is that the cable raisies the line pressure, which as you put more power through the box raises the clamping pressure on the clutch packs - this is how the TH700r4 works and the cable has to be spot on.

So if you imagine you are riding a manual clutch with your foot - you know that you can drive moderatley and the clutch wont slip, but if you floor the engine up a hill the clutch will burn and smoke. In an auto - your foot is replaced with hydraulics - and a low line pressure will cause it to slip under load. (and burn!)

The reason the pressure changes (the cable) is so you get hard firm shifts when flat out and gentle slushy shifts at low/idle throttle. What he is trying to proove is that you get slushy shifts when the throttle is at idle (but actually the cable is removed). So you can drive it normally - just dont lean on it and be aware of it slipping.

Well - thats how the GM boxes work. 700r4 uses a cable, TH350 and 400 use a vacuum modulator.

The chain could be stretched - I had an early formula ferguson xfer box with a streteched chain and you would get clonks at light throttle

[DaveEFI]

The reason he says drive gentle presumably is that the cable raisies the line pressure, which as you put more power through the box raises the clamping pressure on the clutch packs - this is how the TH700r4 works and the cable has to be spot on.

So if you imagine you are riding a manual clutch with your foot - you know that you can drive moderatley and the clutch wont slip, but if you floor the engine up a hill the clutch will burn and smoke. In an auto - your foot is replaced with hydraulics - and a low line pressure will cause it to slip under load. (and burn!)

The reason the pressure changes (the cable) is so you get hard firm shifts when flat out and gentle slushy shifts at low/idle throttle. What he is trying to proove is that you get slushy shifts when the throttle is at idle (but actually the cable is removed). So you can drive it normally - just dont lean on it and be aware of it slipping.

Well - thats how the GM boxes work. 700r4 uses a cable, TH350 and 400 use a vacuum modulator.

The chain could be stretched - I had an early formula ferguson xfer box with a streteched chain and you would get clonks at light throttle

I must admit my experience is not with the ZF 4HP22, but with B-W 35 and 65 which are both also totally cable controlled. However, the principles must be the same? So I can't understand how disconnecting the cable makes the 2-1 roll-out change worse, unless the cable is sticking in some way and not returning to the rest position.
On the B-W box, the actual valve is spring loaded onto a cam and can stick even when the cable appears to return under spring pressure, so not actually making the rest position. But disconnecting the cable wouldn't make this worse.
I do have a 4HP22 repair manual somewhere - I'll try and find it and have a look at how this part works.

[Eliot]

Its a landrover - with two gearboxes, two props and two diffs - it will clonk as there's lots of slack in there.

If its not intrusive and doesn't feel like its doing damage - i would just leave it alone.