FAQ Converting HF2AV Transfer Case into Part Time Transfer Case (1 Viewer)

[OGBeno]

Beno,

it's time to change the year (2009) and the date format (dd/mm/yyyy) on your camera!

Last year was better.



UPDATE:

Short side went back together perfectly.

The measurement for machining the long birfs were money, right on. EPC measurements were correct. 13mm down from the top of a long birf is where the groove should go, with the groove being about 3mm in width.

Aisin's have been installed.

I'm going to bleed the brakes tomorrow, bleed the PS system, and take her for a spin with the steelies and pull the front drive shaft just as a test run. She hasn't been on wheels for almost two months.

 

[coldtaco]

I did this Marks transfer conversion last summer/fall. I can't for the life of me remember the instructions saying anything about welding anything? I haven't driven it yet as the project is still a project

 

[OGBeno]

I did this Marks transfer conversion last summer/fall. I can't for the life of me remember the instructions saying anything about welding anything? I haven't driven it yet as the project is still a project

Kris and I are not using the Mark's spool which replaces the rear case of the diff. which is what you did. We are actually welding the rear spider to the rear diff case in effect doing the same thing.

 

[coldtaco]

Ahh, that makes sense. I guess I missed that part while reading through your post. Thanks.

 

[OGBeno]

Finally got her moving on her own tonight after doing a PS bleed, filling the diffs, and putting the battery in.

She performed excellently with the front drive shaft removed and the center diff lock button engage in 4H. I took her for about an hour drive at all speeds/highway/etc.

I've driven before for significant amounts of time without a front drive shaft, and liked the feel a lot.

With the hubs in the "Free" position it was even better, much better off the line, much more "spirited" (as spirited as a 3 ton truck is going to get). The front end felt lighter as well without the drawn out acceleration that usually is the case for this rigs in 4WD full time. And I got 34 MPG better mileage!

I really like it.

And with the hubs in "Free" I was able, as expected and designed, to turn the front pinion companion flange, so everything is coming together nicely.

Now the final piece of the xfer case modification and all should be kosher!

Later.
-onur

 

[alia176]

And I got 34 MPG better mileage!

-onur

Whoa

 

[locrwln1]

Whoa

I'm with you, I think he was driving his Honda when he saw that mileage.

Jack

 

[70sguy]

Well, the HF1A is a different beast than the HF2A or the HF2AV. The HF1A will have a 3 position shift lever like the 40's and 60's: a 2H, 2L, 4L.

By taking out your viscous coupler you are in effect making your transfer case into an HF2A without the V for the viscous coupler, but it is still a 2 position transfer case.

This modification will not make the HF2AV into a 3 position xfer case, but by doing the CDan 7pin mod, by getting a center diff switch you will basically make the xfer case into a 3 position case via switching as opposed to a lever.

There is actually two versions of the HF1A part time case, the direct shift HF1A is the one with the 3 pos stick ala 60 series. The HF1A in my 80 is electric (ex JMD HDJ81), Stick controls High and Low range selection and uses push button control on the dash and electric motor on the case to engage/disengage front drive in the same way the motor on US HF2AV engages/disengages the CDL. Both versions of the HF1A have the characteristic stubby rear output.

 

[DanS HJ-45]

I've driven before for significant amounts of time without a front drive shaft, and liked the feel a lot.

With the hubs in the "Free" position it was even better, much better off the line, much more "spirited" (as spirited as a 3 ton truck is going to get). The front end felt lighter as well without the drawn out acceleration that usually is the case for this rigs in 4WD full time. And I got 34 MPG better mileage!

Amazing how that works huh? I'm always amazed at just how much noise and vibration comes from all that rotating mass with the hubs engages/drive plates.

You'll save your diff bearings too without it all spinning. Bonus!

OK, I'm back to the old truck sections now that I've seen pictures of the hubs installed.

Dan

 

[OGBeno]

Amazing how that works huh? I'm always amazed at just how much noise and vibration comes from all that rotating mass with the hubs engages/drive plates.

You'll save your diff bearings too without it all spinning. Bonus!

OK, I'm back to the old truck sections now that I've seen pictures of the hubs installed.

Dan

Thanks again Dan. I really appreciate your expertise, assistance, and time.

Hope the line in DEN is doing well for you these days.

 

[cpg]

a real part time 4WD vehicle.

There have been a number of threads talking about do this and do that, but no definitive thread on how to do from start to finish. IBCRUSN and myself have been talking about this for a number of years, and Alia176 already did this to his 80 using a spool in the center diff of his xfer case.

How hard was it to get the rear housing off? It seems to be doweled and has a shaft iside that conects the two pieces together. With the sealant it seems to be glued together with no jack screws. What worked for you?

Thank you

Chris

 

[OGBeno]

How hard was it to get the rear housing off? It seems to be doweled and has a shaft iside that conects the two pieces together. With the sealant it seems to be glued together with no jack screws. What worked for you?

Thank you

Chris

hey Chris:

Well, I have a spare xfer case that I am doing this modification to and will be pulling my extension housing and center case and installing the modified one from the spare.

I used a brass punch and a hammer to get the extension housing off, and then did the same with the center case portion. You will need to be creative if this is attached to the truck still.

Best.
-onur

 

[cpg]

hey Chris:

Well, I have a spare xfer case that I am doing this modification to and will be pulling my extension housing and center case and installing the modified one from the spare.

I used a brass punch and a hammer to get the extension housing off, and then did the same with the center case portion. You will need to be creative if this is attached to the truck still.

Best.
-onur

Thank you.

 

[alia176]

CPG,

it's quite easy to split the case apart. I have various rubber mallets and there are places where you can sneak in a screwdriver or a punch to persuade the case to split up.

The biggest thing to watch out for is that the guts may slide out and bonk you on the head. A simple strap around the whole thing will keep the gears/guts up in the Tcase while you work on the center diff.

 

[cpg]

CPG,

it's quite easy to split the case apart. I have various rubber mallets and there are places where you can sneak in a screwdriver or a punch to persuade the case to split up.

The biggest thing to watch out for is that the guts may slide out and bonk you on the head. A simple strap around the whole thing will keep the gears/guts up in the Tcase while you work on the center diff.

Thank you.
It was actually very easy a couple of taps and it slid right off. Getting the thrust washers to stay in place while putting it back together was a little tricky.

Does that orange fipg need to cure before you add oil?

 

[cstamm81]

I was intently reading this thread... hoping for the full on install to be completed. Any new news on this project? Or was it abandoned?

 

[OGBeno]

Not at all abandoned. Just got the spacers from IBCRUSN (one metal, one plastic).

Had a couple of trips, work intensifying, and some other mechanical issues in the interim.

Was thinking of just taking the rear extension housing off of the xfer currrently on the rig, but now I am thinking of rebuilding the spare and doing an R & R on the xfer. Not sure yet at this point.

I'm in no hurry to do this as I have a lot of projects still on the 80. I hope to have it done this year sometime.

Aisins/birfs have been completed. Just driving it in 2WD with the front DS removed and the CDL engaged.

 

[cstamm81]

Glad to see you are going forward with it. I have been thinking of doing this mod ever since I had to pull my front shaft and run with the CDL engaged for a few hundred miles. Felt like a completely different truck IMO.

Very informative post, and you were right, it needed to be documented. All of the info before seemed matter of fact. Also happy you cleared up the birf machining process and the difference between the earlier and later birfs.

Hmm, whether to use the Marks kit or weld as you did...

 

[OGBeno]

Mark's is tried and true and warrantied and all that fun stuff. Just costs more money.

I can't say that this is going to work. It might not and the xfer case might blow up on me! (doubt it)

IBCRUSN and I wanted to document the DIY possibilities....which we liked much better than shelling out a bunch of cash. Both IBCRUSN and I have little time or little money....gotta utilize the resources available to us!

 

[cstamm81]

seems like this shop ACC Toyota Truck & Land Cruiser
has done a few the same way you are doing it with success. I know at least one of the owners is a member here, and has posted encouraging info. Seems he put a spacer on the back of the newly welded "spool". That seems to be the only thing different from what you are doing.
The Mark's kit is a lot of money when you consider what you are actually getting...
Not sure I know anyone locally I would trust enough to TIG weld this properly. I am going to email ACC Toyota and get some quotes on different things.