Pumpkin swap - Update: Clips are on, new problems

[Dino]

I would like to change my 3.91 gears for 2.94 gears but have never done this before.  Both are 741 cases.  All I have is the diff cover gasket so I need to go shopping.  What else do I need besides gear oil?  

Does anyone happen to have pictures of how to do the swap step by step so I don't mess up?  

I understand I need to raise the car and put the stands under the rails, not the axle.  Pull the wheels and drum brakes, unbold the axle and slide them out 5-10 inches.  Unblot the U joint and the diff housing and pry the botom part to drain the oil, then remove the whole thing.  

So then I clean the edges and put the new gasket in place along with some permatex and bolt the new unit in place. (torque the bols or go by feel?) Then what?  Just push the axles back in and add oil or do I need to do something to the bearings first?  Do I need to adjust the bearing preload at all?

I'm trying to be rpepared for this before I start messing around and end up with a non rolling car in my garage.

[68neverlate]

 

[mpdlawdog]

Ill take the 3.91s if you dont have a use for them  ........I want to do just the opposite!

[flyinlow]

no pictures
2 qts of gear oil 85w-90, suregrip additive,if applicable, dust seals , dial indicator to set up axle end play, torque wrench, wheel bearing grease. service manual

frame rail support or housing is fine, inspect tapered axle bearing and pack with wheel bearing grease before you reassemble. adjustment is on the pass. side for axle end play ,there is a small locking clip, don't lose it. I would replace the inner seals if they are old ,you would need a seal puller. Carrier /axle stud kit available at Mancini if you need it.

I would wait until the season is over and do it during the winter, in case you run into a problem. 

[Chryco Psycho]

Pull the rear wheels & drums , there is a hole in the axle you can reach the 5 nuts holding the retainer plates for the axles , remove those & pull the axles out 3" or more , add grease to the brgs while they are out . remove the driveshaft & the 10 nuts holding in the carrier & use a jack to break the seal , remove the carrier & clean the surface & reverse the proceedure , I use Ultra Black silicone or Right stuff to seal the carrier to the housing , torque the nuts to approx 35 ft lbs

[RallyeMike]

If you are going to be playing with these cars for awhile, get a decent shop manual and use it. It will pay you back many times over. It covers this step by step, and with pictures.

There are a few precautions - like, don't let the axle splines rub on the axle seals if you pull them all the way out - it may create a leaking seal. Be sure to set the axles back in with a good blow from a hammer so that you end up setting your axle load correctly. If the axle isnt seated all the way your axle load will be off. You'll want to use a dial indicator to adjust the axle until you have done a few and get the feel for it.

For the record, you do not have to pull the brakes, so you can save a step there. You have to fiddle with it a bit more to get the axle in and out past the spreader, but it is doable.

[Dino]

You guys rock!  I feel a bit more confident doing this swap now.  I'll have to add a dial indicator to my list, at least now I have an excuse to buy one!   

I do need to do this swap before winter though because I'll be driving it 4 hours away to store it and there's no way I can do that with these gears. 

I'm off to order the service manual, on cd.  Seems a bit easier to print what I need instead of making the actual book all dirty.

[Chryco Psycho]

Duh I missed resetting the end play 

[Dino]

Well I figured I'd start the swap seeing I'd like to drive tomorrow and I wanted the rtv gasket to sit overnight before I fired it up. 

That plan was laid to rest pretty quickly.  First of all I have to do the work on my garage floor and tried jacking up the car by the rear end so I could place some jack stands.  I can't jack it up there because I don't have the room for the jack handle to go up and down.  I'll have to jack it side by side which I don't like doing but what else can I do?  The I noticed the U-joint, both centers are 741's but the one that's on it now has a wider u joint than the one it will be replacing...great...

So I looked at the joint and I can only imagine I need to remove the large nut on both and swap the u joints....I don't even own a socket that large. I can only assume that all I can do is go buy the socket and hope these nuts come off easily?

Right now I'm not to keen of doing the swap, should I just drive to a mechanic and hope they don't charge an arm and a leg?

[RallyeMike]

Swapping the yokes on your pigs is a whole nuther bit of work. It's a bear just to break the pinion bolt loose.

They have conversion U-joints that will connect the big yoke on the shaft to the small yoke on your new pumpkin, if you care to take an easier route. The only thing is that the bigger U-joints are stronger, so you would be losing a little bit there. 

[Dino]

Why I thought this would be easy is a mystery to me...

I will get the socket to at least try and get the pinion bolts off.  Since they both are 741 cases is it safe to assume that the bigger U-joint will fit the other center section or can this be a different spline count? Would you happen to know off hand what the size of the pinion nut is?

I stopped by the local garage this afternoon to see if they could do the work but me thinks the cost will be a little much.  I really need to do this, I'm just afraid to start and get stuck.

[Chryco Psycho]

leave the pinion yolk alone , on a 741 it is shimmed but it needs to be torqued correctly , it is far easier to just use the conversion U joint if the driveshaft & yolk are different sizes

[flyinlow]

+1

[Dino]

Well I did it!  Got the conversion joint, precision part #347, and gathere up the courage to do the swap.  To be honest, the part that was holding me back most was having to jack up the car and be under it, always makes me nervous.  I had 4 jack stands and 2 jacks under the car just to be safe.  I unbolted the 4 small bolts holding the cross shaped joint to the center section to disconnect the driveshaft, removed the wheels and the 5 bols holding the axles in place, slid the axles out a bit and greased the bearings.  Then I loosened the 10 nuts on the center section and gave it a few wacks with a rubber mallet to break the seal.  Had a cup of coffee while it drained!  Removed the nuts, put the jack under the pumpkin and slid it out.  That part was tricky, I had an old plastic basin ready to drop itin which worked out nicely.

Then came the hard part, removing the old gasket which was stuck to the housing.  This took me quite a while with a razor but I got it all off.

I then used ultra black on the housing and made sure to go all the way around the bolts, pressed the new fel pro gasket into it and used ultra black on the other side as well.  Now I had to get the replacement pumpkin into place before the stuff would set up.  After 10 minutes of primordial screams I was aable to slide it into place without hitting the new gasket.  I sude the jack to balance the pumkin and slide it right in.  I tightened the nuts in a star patter but not very tight, waited abit and then tightened it all down.  I do not have a torque wrench so I may have to get one tomorrow unless nice and snug will do.  The ultra black that squeezed out I smoothed out with my finger to get a nice seal, I figured it wouldn't hurt.

I put the axles back in place and put the little bracket back on the passenger side but I have no idea how to set the play on this.  How exactly does this work?  There doesn't seem to be any play on either axle right now.

I also need to remove the old u joint and put the conversion u joint in but don't know how to swap them.  Can someone tell me how to best do this?

Once that is done I have two quarts of castrol 80w-90 to go in and I'm assuming I need to take a short drive and then retighten everything or should it be ok?

Oh and although the previous owner told me I had 3.91's, it was actually 3.55.

Now I have to go find a matching gear for the trans so the speedo isn't off.

[Rolling_Thunder]

 

I have a 3.55 geared pumpkin kicking it in my shed next to a 3.91...      which one to pick       

[Chryco Psycho]

on the passenger side axle where you installed the steel hook there is an adjuster wheel that threads into the retainer plate , with the hook removed you can rotate the adjuster wheel , , you can use a blunt punch a hammer , rotate it counterclockwise until you get some end play then snug it until the play is almost all gone , make sure you tap the axle with a hammer to seat the brg on the opposite side .
On the driveshaft there are clips inside the ears , clean out the dirt & you will see a 3/4 circlip , snap the clip off , I usually use a vice & you can either press the cap out using a small socket on one side & push the cap into a larger socket on the other side or you can set the u joint on top of the vice & use a hammer on the yolk where it si welded to force the cap out of the shaft . Then to install insert the cross of the U joint & use the vice to push the cap in while keeping the cross in the cap so the rollers do not fall out , then do the same with the second cap , you then install the new circlips to retain the caps , you need the circlips on the caps that go into the diff yolk as well to center the U joint in the yolk   

[Dino]

I have a 3.55 geared pumpkin kicking it in my shed next to a 3.91...      which one to pick       

Weren't you going to run a 5 or 6 speed behind that hemi?  The 3.55 would be perfect if I had an overdrive gear, I think you can go pretty high.

[Dino]

on the passenger side axle where you installed the steel hook there is an adjuster wheel that threads into the retainer plate , with the hook removed you can rotate the adjuster wheel , , you can use a blunt punch a hammer , rotate it counterclockwise until you get some end play then snug it until the play is almost all gone , make sure you tap the axle with a hammer to seat the brg on the opposite side .
On the driveshaft there are clips inside the ears , clean out the dirt & you will see a 3/4 circlip , snap the clip off , I usually use a vice & you can either press the cap out using a small socket on one side & push the cap into a larger socket on the other side or you can set the u joint on top of the vice & use a hammer on the yolk where it si welded to force the cap out of the shaft . Then to install insert the cross of the U joint & use the vice to push the cap in while keeping the cross in the cap so the rollers do not fall out , then do the same with the second cap , you then install the new circlips to retain the caps , you need the circlips on the caps that go into the diff yolk as well to center the U joint in the yolk   

Ah setting end play makes sense now! 

I didn't think to remove the driveshaft from the transmission and get the whole thing from under the car but looks like that's what I need to do.  I looked at the box the new cross came in and I see the new clips so I know now what to look for.  Thanks Chryco!

[Chryco Psycho]

Anytime 

[Dino]

Pulled the driveshaft out and removed the 3/4 clips on the insides of the caps.  I don't have a vice big enough to press the cross out so I grabbed a socket just smaller than the caps and one big enough to accommodate the cap on the other side.  Gave it a few good whacks with a big hammer and it moved about 1/16", now it's pretty much there to stay.  I can hit much much harder than I am doing now but I'm afraid to break the actual driveshaft.  How hard can I hit this thing?

[Chryco Psycho]

support the other side with a socket big enough to allow the cap inside & you can hit it hard , penetrating oil will help

[Dino]

support the other side with a socket big enough to allow the cap inside & you can hit it hard , penetrating oil will help

Yep that did it 

Of course I didn't pay attention to where the grease nipple goes and if I need to add grease or not.  Don't have a grease gun so I'll try to stuff some bearing grease in there out of the jar.

[Dino]

Found which way the nipple goes and added grease with a siringe.  I have the clips on the caps in the driveeshaft and placed the clips on the caps that will be strapped down to the rear end, but I can't get the caps to slide into the rearend with the clips on.  When I remove one clip the whole thing slides into place but now I can't get the second clip on, I need help....

[maxwellwedge]

I think a 3.55 is the perfect all around street gear.

[Dino]

I cannot get those 2 c clips on the rear end in place, no matter what I do.  When I slide the u joint in place with one c clip on the cap, the cap does not sit flush with the yoke, it's depressed slightly, the other end the cap protruds a bit and there is not enough room to get the second clip on, seems this joint is simply too long, what gives???  I tried installing both c clips and then put  awoodworkers clamp on the caps to keep everything tight buit no luck, when I try to slide the cross into place, the clips won't fit inside the yoke and one of them will come half off.

I need to get this thing assembled as it is really getting on my nerves.