Step-by-Step 4R70W Automatic Transmission Installation

[chuzie]

First order of business is to remove the D20 from the C4. In doing so, the spud shaft (D20 input shaft) decided to stay with the C4 intermediate housing instead of come out with the D20 and the roller bearings all ended up in the bottom of the C4 case. I had a garage covered in gear oil, so be careful.

I had to completely drain the D20 and remove the inspection cover to retrieve the 13 roller bearings. Used wheel bearing grease to make them nice and sticky and put them back where they belong.



After cleaning up my garage and finishing the bearing issue, it was time to swap the new spud shaft and bearing on the old drive gear.

Here is the old assembly...



The snap ring holding the drive gear on the spud shaft was a real pain the butt since it had no eyelits for snapring pliers. Advance Adapters does not include a new snap ring so destroying it was not an option. I ended up opening it up enough with my snapring pliers to get one end just out and over the spud shaft spline. Then I slowly worked it with a couple of flathead screwdrivers. I tweaked it a little but felt comfortable it was still usable. Someone correct me if I am wrong, but there is not much axial load on that snap ring anyway.



Drive gear removed from old spud shaft and bearing.



Next I had to mate the retainer, seal, bearing, and new spud shaft which are all a pressed fit.

I mated the bearing and shaft first. Since I do not have a press, I opted to place the spud shaft in the freezer for 30 minutes and the bearing in the oven @ 350 degrees for 30 minutes. The two mated like a couple of horny high school kids! Slid right on with no force whatsoever. I would use caution with the bearing in the oven. It was not until after I did this that I called Nachi and asked what the temperature tolerance of the bearing was. Turns out it is 220 deg. F. Keep in mind that is while under load not static in a oven. They are just concerned about deformation under stress so take that for what is worth.



Next is the seal installation into the retainer.

Set the oven to 350 degrees F for the retainer and throw the shaft/bearing assembly and seal in the freezer. Please make sure the shaft/ bearing assembly is cooled before placing it in the freezer!

While the oven is heating up, lay a light coat of blue RTV gasket maker on the retainer where the seal will rest.



Make sure orient yourself with how you will place the seal. You will not have a lot of time once the parts are hot/cold. The open end of the seal is to face the transmission.



Place the retainer (yes, with the blue RTV) in the oven @ 350 degrees for 30 minutes.

Once the parts are cooked, you can install the seal into the adapter ring.

I used a spare piece of 2.5" exhaust tube and a mallet to drift the seal in evenly.



I used the depth function of my caliper to verify it was fully seated all the way around. Next I sprayed a coat of silicone lubricant on the seal lips just to make sure it would stay happy for the duration.



Next is mating the retainer / seal assembly to the bearing / spud shaft assembly.

We want to heat the retainer assembly in the oven at 200 degrees F for 30 minutes to prepare it to be mated the the bearing / shaft assembly. I was concerned about the temperature limits of the seal. I called National and found this seal has a tolerance of -40 / +220 degrees F. The transmission does have the ability to reach the upper end of this spectrum but I seriously doubt that temp would ever reach this seal.



Now the bearing had to be secured in the retainer with the large inner snap ring provided by Advanced Adapter.



Next the drive gear was installed on the new spud shaft assembly and the darn snap ring was reinstalled. It is not any easier installing it now than it was during removal.



I used blue RTV in the channel of the adapter where the new O-ring seats.



Then installed the new O-ring. I also added a coating of silicone to the OD of the O-ring once it was installed to reduce friction during installation to the D20 housing.



*** EDIT: Some folks (including me) have been trimming the gasket that goes between this assembly and the D20 case thinking it goes over the assembly and not under it. Before installing this assembly, install the gasket and no trimming will be necessary. The gasket is dummy proof so it will only go on one way.

After the gasket was on (in theory ), I installed the assembly and gave it a slight tap with the mallet to seat.

Now my D20 is complete with new spud shaft, retainer, and bearing!



Next, I installed the ZF adapter ring. All 6 holes line up in all configurations but the adapter does have a dimple that goes at the 12 o'clock position. The 6 allen head bolts secure it to the D20 case.



The gasket that goes between the ZF adapter and the transmission is dummy proof too, but not as obvious. Just be careful to make sure that all 6 holes are lined up. The ZF adapter has 6 sets of 3 holes each for multiple clocking options. I just did as others have in the past and went with the middle of the three holes.The normal torque rating is 45 ft-lbs but since this is an aluminum adapter, I decided to reduce that to 30 ft-lbs. Advanced Adapters does not provide torque specifications in their installation instructions so this seemed like a good strategy. I ended up stripping out 3 of the holes!

I called Advanced Adapters and they suggested I Helicoil the damaged hole. Of course I had no Helicoil set in the garage. Now I can add $30 to the cost of the conversion for a Helicoil kit.

I went ahead and used Helicoil in all six holes because I know they are all weak and the last thing I want is to strip out another hole especially after it is installed and I go back after a few hundred miles to retorque.




I marked the gasket to the ZF adapter to make sure it didn't rotate during mating to the 4R70W. To my surprise, it slid on rather easily and I had it bolted in no time.



This is a good time to install the flex plate to the engine.