The Pantera Place
"Your de Tomaso Connection"

Leak-proofing The ZF Transaxle Yourself

By Mike Dailey,  February 6, 1999.  

(A condensed version of this article was published in the May 1999 POCA Newsletter)  

Jack DeRyke published an article in the May, 1998, POCA monthly news letter on do-it-yourself leak-proofing of the ZF transaxle. Jackís article inspired me to consider a do-it-yourself approach to my Pantera ZF transaxle.

I wondered if I had unknowingly contracted Pantera fever and whether the "fever" might be causing some kind of delusion of grandeur - but on the other hand, I wasnít really planning to take the ZF transmission apart. Well, not completely apart. What follows is my experience with my ZF and some thoughts that might expand on Jackís article.

Most of the leaking from my ZF was coming from the front seal. The folks at ZF engineered the front seal assemble pretty well, as the seal hosing has an oil drain hole on the outer side of the seal and an oil slinger on the main shaft that keeps leaking oil at the drain hole. Resulting in the oil running down the face of the front of the transaxle inside the bell housing and out the hole at the bottom of the bell housing. Although the front seal on my ZF had started leaking badly, there was no oil on the clutch.

Before starting the project, Jack and I exchanged some e-mail about his article and I spent some time talking to Pantera Performance in Colorado. In my case, the ZF leaking was my only issue, because the transaxle shifted just fine. Talking to Pantera Performance, helped me determine that they could reseal the transaxel at a reasonable cost. However, I decided that if I went to the trouble of removing the ZF and sending it to Pantera Performance, I might as well go completely through the rebuild process. Other major issues of consideration were the shipping cost of $300 and the down time of the car of no less than three weeks.

The other issue that I was pondering, was what level of rebuild on the ZF should I undertake? Itís really an all or nothing proposition, all of the synchros, etc. Pantera Performance listened to my description of the transaxle condition, the limited mileage I drive per year (about 1,000 miles) and to my surprise, they agreed that if I got started on the project and got in over my head, that I should just button it up and send it to them to finish the work. At this point, I had little to lose on the do-it-yourself plan because I needed to remove the ZF anyway. After I talked to Pantera Performance, I developed a great level of admiration for their honesty! So - of course, I ordered the front seal, the right and left axle seal, a new fill plug and the side cover gaskets from them.

Pantera Performance recommends RTV for the lower cover gasket and for the front shaft gasket. My ZF did not have a gasket on the front shaft. While I had the ZF out, I decided to replace all of the clutch stuff - roller pilot bearing, clutch plate, pressure plate and throw-out bearing. I used stock clutch parts from Pantera performance.

Before starting, I recommend that anyone undertaking this project, clean the outside of the transaxle and then drive the car to induce leaks and make sure that you can identify all of the leaking areas on the transaxle. In my case, the transaxle was clean because Iíd been cleaning off gear oil for months and I certainly knew where the leaks were.

The first near disaster on the project was caused by the information provided in the Ford Pantera Technical Information manual. The manual instructs that a "protected floor jack," be placed under the engine as far back on the oil pan as possible to raise the back of the engine removing the load on the back transaxle mounts. DO NOT JACK ON THE OIL PAN! The oil pan is soft metal and can be crushed into the crank shaft of the engine. I was very lucky and used a very large piece of wood to protect the pan which made a very small depression in the pan with no negative result. I understand that it does not take a very big depression to have the pan hit the crank. Wow, lucky me! A better solution would be to jack on the sides of the engine block as descried later in this article.

By using the Ford Pantera Technical Information manual, I was able to remove the ZF by myself. I spent one evening getting everything ready for the hoist and then rented the hoist and removed the ZF. My car has an aluminum adjustable wheel house brace so I made a small jig out of cardboard that fit between the two arms allowing me to adjust it back to the same position.

Mike working on ZF.jpg (49824 bytes)

Getting the old clutch plate out

My transaxle was very clean so I did not need to do much cleaning before I started the disassembly. There are some areas behind the side plates where dirt collects that cannot be easily cleaned out before removing the bottom cover and side cover. Care must be taken to clean this area with the side plate removed. Keep everything clean and do not allow any foreign objects or dirt to get inside the ZF case.

I cleaned the inside of the bell housing with engine degreaser and carb cleaner. I found that carb cleaner and paper towels did a great job of super cleaning all of the outside areas of the bell housing and transaxle.

I found that the only way to get the front seal out of the housing is to fold the edges of the seal over and using the dikes, cut and pull the seal apart. Be careful cutting the seal with dikes as part of the front casting looks like it is part of the seal, and it isnít. Make sure that the front main shaft bearing is fully in place in the front of the case. The front bearing can work its way out of the case and slide back on the main shaft making for a very leaky front seal. This can be seen with the front housing off and from the back side with the lower cover removed. In my case, the bearing was fine.

I used the slide hammer puller to remove the throw-out bearing from the carrier while the carrier was out of the transaxle. I cleaned the carrier inside and out and installed the new throw-out bearing. I packed the inside grove of the carrier with grease and put grease on the tabs where it contacts the release arms. Make sure that the ends of the throw-out bearing retaining spring does not hit the mounting flange for the front housing. Check the tightness of the bolt and nut holding the clutch shaft arm on the outside of the case. The nut on my arm was finger tight. Also check that the arm and nut does not bind on the side of the bell housing when the arm is moved through its full movement.

ZF front view with throw-out-bearing removed (this view is before cleaning and the ZF is upside down)

The side covers must be removed to install the axle seals because the axles are held into the side covers with circlips. I removed one side at a time, completed that side, reinstalled, torqued and then removed the other side. Keep in mind that you are messing with the side covers that support the ring gear and control the ring and pinion gear lash adjustment. You will need circlip pliers that are long enough to reach down into the back side of the side cover to remove the circlip that is around the axle. You might want to hold off purchasing the circlip pliers until the side cover is off so you can see how long they need to be, and the size of the plier ends.

I found it hard to get hold of the clip on the first axle, move it out of the axle groove and start moving it up the axle. The second axle went a lot easier. There is a spacer washer behind the clip that must be removed. If not removed, the spacer will catch in the circlip groove and get bent when removing the axle. This was almost disaster number two for me. At this point the axle is ready to be removed. I held the side plate with the splined axle end down and lightly tapped the whole assembly down with the splined end of the axle hitting on about six layers of a towel covering the clean concrete garage floor. It sounds crude but I did not have a press. In my case the axles were a snug fit but came out pretty easily.

It appeared that the only way that the seals were going to come out of the side plates was by using a slide hammer seal puller. I bought the puller for the seals but you will need it and some strong arms to get the clutch pilot bushing out of the crankshaft anyhow.


Outside and inside view of the side plate

I inspected each new seal carefully before installing them because you do not want to do this a second time. Check that the seal lips are smooth, not damaged and that the seal spring is positioned inside of the seal. The new seals had an inner and outer lip and griped the axle slightly further out on the axle than the original single lip seals. I used a strip of 3M Crocus cloth to lightly polish the axle area where the new seal would have contact. After the seals were installed I coated the axle and the inside lips of the seal with gear oil, slid the axle back in (make sure it starts in straight), tapped into place, reinstalled the spacer and installed the circlip. I made sure that the circlip was fully seated into the axle retaining groove 360 degrees around.

My ring gear had been safety wired by a previous owner so I inspected the safety wire work, the ring and pinion gear and all of the rollers and races that were exposed when it was apart. Everything inside the case was very clean and looked good, no pitting or indication of problems.

View with  lower cover and one side plate removed

My ZF also leaked at the back cover stud nuts, the lower seam of the back cover to transmission joint and out of one of the lower bolts that hold the front and back half of the transmission together. By now my confidence was running high and I was ready to tackle the back cover. Containing my enthusiasm, I decided to talk to Pantera Performance as I would need a back cover gasket. They quickly convinced me that I might be heading into a dark ZF abyss so I decided to remove one back cover nut at a time clean, seal and re-torque. This fixed the leaks including the lower seam problem. I am not sure if the gasket was really leaking before and re-torquing fixed the problem or if oil collected there from the leaking studs. I did not need to reseal any of the detent bolts because they were not leaking.

Getting the clutch pilot bushing out was tough. I used the slide hammer puller but only one hook would fit inside the bushing hole. Once you start pulling, the bushing gets damaged so there is no going back. This was almost disaster number three! I kept moving the hook to a new position and banged away. I finally got it out, cleaned up the opening, wiped in a very small amount of light oil and tapped in the new roller bearing. I used a plastic clutch alignment tool that I purchased at Advance Auto Parts to position the clutch plate and assembled the clutch.

New clutch installed

A friend helped me install the ZF back in the car. We spent some time talking though the steps for getting the ZF back in the car before we started. During installation I used a hardwood block and placed it on the left side of the engine on the inside of the left frame rail so I could lift on the heads of the pan bolts. Be very careful not to catch the lip of the pan (no more jacking on the pan for me). I lifted the back of the engine just a small amount to help with the angle when sliding the transaxle in, and to get some extra space between the back of the transaxle and the back body of the car. On early Panteras with the back transaxle mount the space between the back of the transaxle and the back lower body of the car is very limited. After the transaxle was in and bolted to the engine, I used the hoist to lift up the back end of the transaxle to install the back mount. This arrangement puts minimal strain on the engine jack because at no time was the full weight of the transaxle on the hardwood block under the engine. I think this approach would also work for the removal steps as well.

ZF-2 transaxle ready for installation

Before installing the transaxle I aligned the transaxle main shaft front spline to match the spline on the clutch plate and then put the transaxle in gear. As the transaxle is guided into the clutch much care must be taken not to force the fit. When everything is aligned correctly, the transaxle magically just slides in. The transaxle is heavy and can easily bend the center splined part of the clutch plate, so go slow and easy. I wiped a very, very, light film of grease on the front shaft spline of the transaxle to help things slide together.

Filling The ZF With Gear Oil

The ZF uses SAE 80W-90 limited slip gear oil.  The brand that I use is Castrol Hypoy C SAE 80W-90 limited slip gear oil.  Before filling, clean the magnet and the recess on the inside of the drain plug.

ZF 102902 1.JPG (40325 bytes)

When the ZF is completely drained it should take 7 1/2 US pints to refill.  The ZF must be filled very slowly to make sure the gear oil has time to flow and level throughout the transaxle.

ZF 102902 2.JPG (41083 bytes)

The early -2 ZFs have a neat little plug on the top for filling and also have side fill plug. The newer -2 units use a side fill plug only.  The side fill plug is used to determine when the ZF is full.

Tool 1.JPG (40160 bytes)

A special 17 millimeter socket for removing the ZF side fill and drain plug is available from Pantera venders.  The one pictured is a Snap-on brand.

ZF 102902 3.JPG (35933 bytes)

The 17 millimeter socket is used to remove the side fill plug that is located on the back driver side of the ZF.  The ZF must be filled very slowly to make sure the gear oil has time to flow and level throughout the transaxle and to keep it from running out of the side fill plug before it levels in the ZF.  When the ZF is full the gear oil will run out of the side fill plug.  Do not over fill. 

I followed the published recommendations to adjust the clutch linkage free play. I like to keep the free play as small as possible for best shifting and I check the clearance often.

There were a few challenging moments during the project but overall, I am very happy with the results. The transaxle looks good, works great and has no leaks. The transaxle is shifting smoother than before the work was done. The improvement is most likely from all of the new clutch parts and less slop in the clutch arm. The new clutch parts also provide for a more exact free play adjustment.

This project is not for everyone or for every ZF transaxle. If you are uncomfortable with the do-it-yourself concept or think your skills are not up to the project, get professional help.

January 31, 2000  Project Follow-up

After about a year of driving or about 550 miles I found a small ZF oil weeping problem on cover #130. This is the small rectangular cover on the right side, toward the back of the transaxle that covers the internal selector fork adjustment set screws (the cover can be seen in the image above located behind the speedometer drive).  I removed the cover cleaned and sealed it carefully with RTV.  This cover was not resealed on the original project.