Transmission Diagnosis & Repair

General Diagnosis
If the vehicle rolls while the transmission is in Park, there is a transmission problem since the parking pawl should hold it. This problem is not too bad to fix since it can be accessed from the rear. If the transmission makes noises or has unusual shift behavior, or for any other reason excites your suspicions, you can try the following quick check. Place the vehicle in park WITH THE PARKING BRAKE ON, put your left foot FIRMLY on the brake (the vehicle should not be pointing at anything you don't want to hit), then rev the engine while watching the tach. The tach should not exceed 2000 rpm. If it does it's time to think about a new transmission. If there's a noise, stop... also time to buy a new transmission or torque convertor! Do not do this test for more than a few seconds. Promptly let the power off and idle the vehicle for a while to let the transmission cool (or drive around under light load for a few minutes). Excessive testing like this will trash the transmission even if it doesn't already have a problem! (This can be done for each gear).

Rebuild/Replacement Options
When Dave Brown had transmission problems, he received quotes for as much as $3,000 for a rebuild. He finally found a local trans shop that had experience with the ZF 4HP22, and they charged around $1200 plus any extra parts not included in the rebuild kit. He needed a detent cable, and total price with R&R, towing, new (rebuilt?) torque converter was just over $1300. This was "State to State Transmission" in Phoenix Arizona.

Dave also reports that he discovered there is a "kit" to allow the front clutch pack to "bleed down" (depressurize) when you take it out of gear. This is a design fault in the ZF transmission that can cause extremely rapid wear of the front "A-pack" clutches. Basically, after the system has been "pressurized" by putting it in gear, and you THEN (in "P" or "N") rev the engine for any extended time (i.e. emission testing, cam breaking in, A/C recharge, etc.) the front clutches can blow. A good shop should know about this weakness and the repair necessary. (Dave thinks it might involve drilling a small bleed hole in some part of the innards).

Selector Switch Problems (4.0/4.6)
On the electronically shifted version of the transmission used on the 4.0/4.6 model, the selector switch mounted on the side of the transmission sends signals to the transmission ECU to tell it which gear you’ve selected. When if fails and starts sending false signals to the ECU, symptoms include giving false and sometimes rapidly changing readings of what gear you are in, and in extreme cases it can default to making the computer think it is in "R", preventing you from starting the engine. Diagnosis and repair of this problem is covered in detail on the separate Transmission Selector Switch Repair Page.

Symptoms & Repair of Upshift Problems due to Centrifugal Controller/Governor Malfunction
Winfried Schoepf suddenly experienced shift-up problems on his 1989 Vogue Auto 3.9 EFI. He would have to rev up the engine to 4000 until the ZF 4 HP22 decided to shift. Alternatively, it helped to drive for 3-5 minutes at 20 mph, then accelerate. Once it had done it, the problem quickly went away. For a short while, it then would not shift down to first when stopping, but after a further few minutes drive and a few stops everything was back to normal. This problem gets worse with time, and the cause is the governor at the rear of the auto box. This is a kind of centrifugal controller for gear shift operations.

Winfried reports that fortunately, this problem is a relatively easy fix. You have to remove the transfer case but not the auto box. Winfried sourced all the parts directly from ZF Austria, using their parts manual for Range Rover. The Auto box serial number is required to get the correct parts. If you have a proper car lift and a transmission lift with special mounting plate for the transfer box, two people are sufficient. If you do not have a proper transmission lift, have two friends ready to take the transfer box off and on, while a third works the bolts! It is a heavy beast and you must not foul the splines. Winfried offers the following instructions:

1. Follow the preparatory procedures for transmission removal. Pay attention to remove the fan shroud or remove the fan rotor because you will tilt back the engine. 2. Remove the transfer box
3. Now you have got the rear side of the ZF accessible for work
4. Disassemble as needed to get access to the governor and pull it gently off the shaft.
5. Remove the 3 rings on the shaft and clean everything (with auto boxes, surgical cleanliness is a must)
6. Fit 3 new rubber seals one the shaft (careful, they are square and must fit precisely, quite a puzzle) using vaseline for greasing
7. Fit a new governor valve complete with valve housing (the one that sits around the shaft), don't bother to fix the old one, it will not work although it appears to slide smoothly. But you may re-use the counter weight of the valve housing. Be very careful when sliding on the valve housing onto the shaft, use vaseline and don't foul the seals.
8. Use new gaskets and refit all the rest
9. While you are at it, remove the ZF transmission sump (well, drain before) and replace the steel mesh oil screen. Check for debris in the sump as a sign of impending clutch failure. A small amount of soft dark stuff is okay, just about as much as would fit under your ten finger nails.
10. Don't forget to refill all oils before firing it up. Enjoy your smooth gear shift again!

Parts cost was about $130 and time spent 5 hrs for two people. If you just drive it into your favorite transmission shop to have it all done, expect about $1500.

Symptoms and Repair of Transmission Seal Problems
Todd Pfortmiller reported in with the problems he was having with his transmission, which turned out to be due to worn seals. "Upon startup, the vehicle drives fine for a little while. Then as the transmission fluid warms up, after a complete stop Drive will not drive. It feels like a little lunge, but that disappears immediately. A quick manual down shift into 1 to engage the mechanical linkage (as I understand it), gets the beast going again. Up shifting 'manually' works fine, and even a severe kick down at highway speeds to climb an 8% grade is not a problem."

Todd's Land Rover tech suspected the three governor seal rings (RTC4660). This turned out to the case -- and the repair procedure is described on the separate Transmission Seal Replacement page.

Warning: Care Needed when Reinstalling Engine or Transmission
Nathan Tucker offers this warning based on his experience of the transmission pump being damaged in the process of replacing the engine. He reports: "I removed the engine for a little work and never removed the torque converter, but alas it slipped a little on the slines that it sets on and during the refitting process I inadvertantly pushed the TC against the pump in an incorrect manner and upon start up of the engine broke the drive gear of the the pump making replacment neccessary, and totally negating the savings from removing and refitting my engine. I ordered a rebuilt pump and had a shop install it to the tune of $900. The couple of shops I called when trying to diagnose the problem (which was not enough pressure in the trans and thus making all gears act as if they were neutral) said that to be absolutely sure that the TC is fully seated correctly that they actually stand the trannies on end. I personnally have never seen it, but they said there are some that are real 'touchy'. I didn't notice anything incorrect when refitting the engine, nor did the work-shop manual mention anything about the TC, only that it must be 50cm from the end of the bell-housing. I have replaced/installed about 3-4 engines in mostly older american cars and never had any problems... "

Transmission and Overhaul Parts Sources
Gasket, Seal and Overhaul Kits
Todd found the seal kit cost $150. FOr the adventurous, I found a complete Range Rover transmission overhaul kit is available from ExpressAutoparts.com for only $38, containing Gaskets; Seals; O'Rings; & Sealing Rings. A Master Repair Kit for $72 contains these items plus Friction and Steel Clutch Plates, Oil Filter, Vacuum Modulator, Front Pump Bushing, and External Housing Bushing. For a job of this importance you might want to go with a Rover parts specialist; Atlantic British has a range of gasket and seal kits for this transmission starting at $119.

Complete Transmissions
If your problem cannot be solved this simply, do not despair as complete rebuilt transmissions are becoming more affordable. For example, Atlantic British has them for $3795.
The very same ZF transmissions are used in many other vehicles, some transmission rebuilding and parts houses also have them. Dwight Smith found a very low cost generic source of the ZF 4hp22 and 24 -- Phoenix Remanufactured Transmissions. In November 2004 Dave Foster reported that he got one there for his 2001 Classic for $1,050. They also ave the electrically shifted 4HP24 used in the 4.0/4.6 for $1,250. Phoenix is a major rebuilding and parts house, and all their remanufactured transmissions are dyno tested and warrantied.

More Information
Transmission Service Page (Classic)
Transmission Service Page (4.0/4.6)
Transmission Seal Replacement Page (Classic, 4.0/4.6)
Transmission Selector Switch Repair Page (4.0/4.6)

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Page revised February 2, 2012