Salvaging (Early) Round Top Cover NV4500

[Richard2112]

Most problems with the early round top trans covers can be resolved by purchasing the new part required. There is one condition that I haven't seen a solution to yet and that is the shifter stub seat worn out. I think there may be a solution to this also. At least it has worked for me. So far.

I have read some excellent threads penned by the members here, some of which have (and yet will) spare me agony of catastrophic failure, economic attrition or at least undue agony while I plod through the restoration of a 1970 C-30 dually. My expertise at turning a wrench has been limited to knowing which way to turn the bolt depending upon whether one desires to tighten or remove it. Basically, I'm as green as they come on the subject of transmission rebuild and replacement so any advice or critique is welcome. If I can do it, then nearly any one can, provided the idea is sound. I find that I have to work on a very restricted budget and should a situation arise that I wasn't prepared for, I better be able to devise a working solution.

Well, that has happened. When I bought my NV4500 I knew it was a high mileage part. I expected to do the typical rebuild, replace synchros, bearing, seals, hubs, rings and springs and things...And there is a lot of good advice on how to do that from people more qualified than me. Some have advised me to just buy a rebuilt trans and be done with it. Good advice to be sure but my curiosity for whats inside the mechanical box over turned the vote put forth by common sense.

Nevertheless, I am arriving at a point that I understand a great deal more about trans rebuild/swap than I did before, and that was part of the goal. One of the things I learned is that the shifter stub seat on the round (early) style top covers will wear. That thought might have been obvious to more experienced people but it was a secondary notion (at best) when I considered my rebuild. The trans I eventually bought came as an assembly, though it was evident the covers had been removed some time long passed and the shifter which came with it had simply never been returned to it's moorings. I figured these things were to be expected. It wasn't until after I had performed a good cleanup on all my parts, rebuilt my main shaft assembly and began to put it all back together that I discovered the top cover was headed for the recycle bin.

A new top cover assembly can easily cost 400 dollars or more, an expense that isn't always necessary or in my case, well outside my budget.

This '93 had seen many miles which was evident on disassembly and the top cover had seen better days.The shifter stub had worn into the seat and as you will see, the bottom of the shifter was wearing into the center rail so much that it locked the shifter from moving.

While working on the top cover, I discovered one of the shifter pins that the stub pivots on, was also broken. And while I could have purchased a small parts kit to fix the broken pin, the seat was still a problem.

To my knowledge (and I searched high and low) there seems to be no method to repair the seat inside the shifter stub tower on the one-piece, round style top covers. What follows is a brief description of how I managed to solve this problem and quite possibly save a few hundred dollars (that I didn't have anyway). This worked for me and maybe it can help some others but it has yet to be time tested. I think it will last at least as long as the transmission but given that I've never run across this technique before, that's just a weighted guess. I'll try to be as clear as possible and answer any questions as well as I can.


The beginning

This is the top cover I'll be working with throughout this write-up. It will go through some changes

[IMG][/IMG]

[Richard2112]

TC gets a bath
Boiling water and Dawn dish detergent cut away most superficial debris.Then a good wash with carb cleaner and engine degreaser. Diesel fuel works well also



Then an acetone rise. Using a one gallon can of acetone I rinsed the TC until the acetone ran clear. (about 4 times)





And finally, after much elbow grease and sweat equity, I have a reasonably clean part. Washing alone did not produce this result. Hours spent with wire brushes and a cordless drill also helped.




Add a coat or three of caliper paint, lube the internals and we're good to go ...right? Wrong. I just couldn't be that fortunate. In this picture, a close look down the throat of the shift tower shows the original pivot pins for the shift stub. At this point, I had not yet tried to attch the shifter to the top cover. And having put that much effort into cleanin' it up I wasn't ready to throw it in the trash.


So begins the repair of the shifter stub seat.

[Richard2112]

The Kit
These are the parts I used to effect the repair

A= Is the first mistake I made. (Well, not "ever" but...) It is a 2 inch bolt, 7/16 x 14, grade 8 with the head cut off. But the bolt had a smooth shank about an inch above the threaded portion that you see in the picture. I cut the smooth shank portion off along with the head of the bolt. Don't Do That. Just take a hacksaw or an angle grinder or the abrading device of your choice and remove the bolt head only. Keep as much of the shank as possible (for now). You'll see why shortly.


B= The two replacement pivot pins. They are roughed in but you can see the length has been shortened and the the end has been reduced in diameter.

C= The hemispherical shim but since I dont like to type, I'm calling it a "cup". It is a stainless steel shim that goes inside the shift tower and the shifter stub rests on it. The cup is made to slide over the end of the shifter stub.

D= The centering tool. More on this later.

[Richard2112]

The Cup
I slid the cup onto the stub to help clarify how the cup is installed.

#Note the finished pin laying on the bench also. A slot has been cut into the head (remaining shoulder of the bolt shank) and the reduced end has been chamfered.

[Richard2112]

Here is a look straight down the throat of the shift tower. You can see the shiny metal where the shifter has worn into the center rail. This was preventing the shifter from shifting. The cup will lift the shift stub just enough to clear the rail. Also note the original pivot pins are gone. I drove them through with a punch and a small sledge.

[Richard2112]

After the pins were punched out, I opened the holes out in three steps, working up to a 23/64 size bit or 0.3680. These are the bit sizes (pick one) that allows for a 7/16 x 14 tap.



I know, I was supposed to use tap oil. I didn't wear safety glasses either. Now that we're punched, drilled and tapped we need to use the bolts to make the pins.

[OregonNed]

Sweet refurbishment! Turned out awesome!

[Richard2112]

Originally Posted by OregonNed

Sweet refurbishment! Turned out awesome!

Thank you, OregonNed. For the money I have tied up in this rebuild, I could have just bought a rebuilt trans. But then, I wouldn't be able to provide much feed back to the forum. The TC shifts really smooth and indexes into the gear pattern with a decisive "Click". Kinda like a bolt action chambering a round.

[Orange Crate]

Richard,
You win the "American Ingenuity" award for this month. Awesome write up.

[Richard2112]

Originally Posted by Orange Crate

Richard,
You win the "American Ingenuity" award for this month. Awesome write up.

Thank you sir. It is good to know that regardless if the thread actually helps some or not, at least it hasn't bored them!

[Orange Crate]

I have a round top NV4500 that needs a rebuild before I install it.

[Richard2112]

Originally Posted by Orange Crate

I have a round top NV4500 that needs a rebuild before I install it.

I am still hoping that I do not have to rebuild my top cover. I believe it is in fair shape. The forks look good and the rails look straight. The pivot pin and the seat was worn.

[Orange Crate]

I meant rebuild the whole transmission, syncro's, bearings, bushings ect. It seems to shift OK just sitting on the engine stand, but I will take a look at the pins you remade and the location to the lower boss where yours made contact (now shimmed with a "spoon" ha).

[Richard2112]

Originally Posted by Orange Crate

I meant rebuild the whole transmission, syncro's, bearings, bushings ect. It seems to shift OK just sitting on the engine stand, but I will take a look at the pins you remade and the location to the lower boss where yours made contact (now shimmed with a "spoon" ha).

What year/model are you rebuilding" Synchro reverse?

[Orange Crate]

It is a 1993 with 6.34 1st gear. It is 4X4 and I have a 6 bolt round NP205 that mates with it nicely. I did buy a cast iron adapter just for the added peace of mind. I have yet to buy the TH400 input shaft for the NP205 and then of course the NV4500 rebuild kit also. I'm obviously in no hurry as my TH350 still works just fine.

[Richard2112]

Yeah I hear the cast iron housings are a good upgrade, especially for the 4x4. I'm doing a 2wd so the complexity of my project is reduced to minimal. Once the trans is rebuilt I just plan to drill my case for the BH bolts, shorten the drive shafts and tweak my drive line angle.

I plan on doing the entire rebuild without any "special tools" but a heavy duty pair of snap ring pliers woulda paid for themselves in spades on the heavy ring.

[Orange Crate]

Pictures of the install are mandatory.....!

[Richard2112]

Originally Posted by Orange Crate

Pictures of the install are mandatory.....!

Haha! Where's the pics of your rebuild? Yeah, I plan on posting pics of the install, both the successes and the not so successes.

I had hoped to post a tutorial on my rebuild but I'm not confident that I can do as well as the ones that others have posted and I don't want to muddy the waters.

However, I might start a thread on how to make certain simple tools that make the rebuild possible, depending upon whether one wants to purchase or make the tools. Getting the bearing cup outta the input bearing retainer (for example) can be done with a metal disk and a large socket. Otherwise, I'm uncertain how to do it without the specially made puller.

[Richard2112]

Photobucket blows.

[saxart]

Another example of a GREAT thread turned to dust by the lovely folks at PB.

[dmjlambert]

It would be nice to see pictures. The uploading of pictures to this forum works pretty well.

[Orange Crate]

When I replied to this thread two weeks ago all the pictures were there, not sure how this works through PB. Are PB pics only available for a short time? Hmmm remind me not to use PB....oh wait I don't know what it is anyway......I guess I'll just keep uploading pics from my computer....

[dmjlambert]

Originally Posted by Orange Crate

Hmmm remind me not to use PB....oh wait I don't know what it is anyway

It is photobucket.com
That is a website where you can store your photos and share them for free. They recently started campaigning their users because they changed their operating model. You can still host and share pictures for free, but they changed so you need a buy a subscription to embed photos on other web sites (like this one). If you want to share pictures on the free account you have to give a link so the user goes to the photobucket.com web site, like this: http://s1245.photobucket.com/user/dm...?sort=3&page=1

[Richard2112]

I could fix it (I think) by uploading directly from PC. But, I cant edit the posts so it looks like It's stuck as is. Oh well.

[Richard2112]

The photobucket fix works! Nice.