Converting a Dana 44 to PosiTrac

[okc63avanti]

The Dana 44 rearend of my Avanti is currently a 3:31 ratio limited slip differential. My plans are to convert it to a 3:73 ratio PosiTrac and use the Fairborn flanged axles. What is done internally to the gears in the differential to convert it from limited slip to twin traction or PosiTrac?

John


63R-2386 under restoration & modification

[Mike Van Veghten]

Same, same, same.
Just different words to describe the same basic part/ring gear carrier.

Different corporations used different words to describe their "Limited Slip" differential assemblies.

Mike

[sweetolbob]

John

Just had my 83 Dana 44 out of the Avanti converted to Posi.

It took:

Auburn Pro posi
Bearing and seal kit
Richmond ring and pinion 4:10 ratio

Parts approx $700 install $150. And my guess is that is about the bottom end of the price scale unless you do it your self.

It is being installed today by me and should be on the road next week so I can probably let you know then how it works.

Bob

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[Guest]

A true posi and a limited slip are different animals. Lslip allows slip around corners and is better than open differentials as far as traction on asfault goes (lousy on ice or snow) True posi (like a lock rite) slip via a ratchet type of arrangement. The wheels both turn the same direction but DIFFERENTIATE through a ratchet that allows different speeds going around corners but when you step on it power goes to both wheels. Lslip given enough burnout MAY transfer power to one. Lockers can be noisy, latest generation lokrite is the better one. Also sold as richmond gear I believe. I hope this helps.

[bams50]

Very interesting. I learned something about terminology in this thread[^]

Robert (Bob) Andrews- on the IoMT (Island of Misfit Toys)
Parish, central NY 13131

GOD BLESS AMERICA

[okc63avanti]

quote:Originally posted by sweetolbob

John

Just had my 83 Dana 44 out of the Avanti converted to Posi.

It took:

Auburn Pro posi
Bearing and seal kit
Richmond ring and pinion 4:10 ratio

Parts approx $700 install $150. And my guess is that is about the bottom end of the price scale unless you do it your self.

It is being installed today by me and should be on the road next week so I can probably let you know then how it works.

Bob

,

Bob,

Thanks for the details. I posted the question once before on the forum and got the new ring and pinion gear answer with no details. Please do keee me informed on how it works out. I'm thinking with all the different brands and models of cars out their that used the Dana 44 there should be a wide range of options and prices. I think some Jeeps used the Dana 44 as well.

John


63R-2386 under restoration & modification

[pgothard]

Another excellent source for all things Dana 44 - including posi/Lslip units is: "DTS - Drive Train Specialists"

Be prepared to find many choices there. You may have to talk to their tech guys to pick the right unit. Just Google the name for their website. I'm planning just such a conversion in the near future.

--Paul

[Rosstude]

First, I am not an expert in this, just have a little experience from several Jeeps, and a Scout or 2.
Your choices for new units are limited by the Stude axle spline count (19 if I recall). Being cheap, I installed a used Stude twin-track, after I priced a new unit. The Jeep sites have a wealth
of info.

[img=left]http://i52.photobucket.com/albums/g27/Rosstude/OldWorld2005002.jpg[/img=left]
Ross.
Riverside, Ca.
1957 Provincial X2
1958 Transtar

[Dan Timberlake]

"A true posi and a limited slip are different animals."
As former president Clinton said, "It depends on what the meaning of the word 'is' is."

There are unfortunate and confusing differences in terminology and function between manufacturers and even era to era.

The folks that make the LockRight ( Richmond Gear ) consider it a locking differential, real good for demanding off road use, but not smooth enough for general street use.

http://www.richmondgear.com/powertrax/lockright.html

They have another product (Powertrax) for which they make this claim - " It combines the smooth operation of a limited-slip differential, with the traction performance of a locking differential." And feel it is the "ideal solution for just about any light truck, sport utility, and muscle car on the road today."

The 1958 Studebaker Shop manual supplement describes the TT action relying in part on ramps that push the Cross Pins (that support the pinion or spider gears) outward to apply force to a series of clutch discs. The 1959 --1964 Studebaker Chassis parts catalog (page 306, illustration number 1004-40) show 5 of 6 friction plate arrangements for TT differential including one belleville spring. I believe the TTs action is essentially the same as GM's Positraction of the era, a clutch type limited slip or "improved traction" differential

In 1962 the Positraction behind a Chevy 409 ( or Turbocharged Corvair Spyder) would have been a clutch type limited slip type, with the clutches preloaded (to be statically non-slipping to about 50 lb-ft of torque) by disc or coil springs, and augmented when driving by a wedging action somewhat proportional to applied torque from cross shaft ramps or just the side gears themselves.

http://carburetor-manual.com/images/1957-Chevrolet-positraction-2.JPG

Sometime maybe in the 80s GM introduced gov-loc posi that used a speed sensing counterweight to defeat the limited slip function at higher speeds, since like others said, when driving at on ice or snow a simple preloaded posi acts like a locked rear axle and can contribute to fishtailing. If I'm already going 30 mph I don't need 2 wheels worth of propulsion, but do appreciate the stability of lateral traction from at least one non-spinning tire.

http://images.cardomain.com/member_images/12/web/504000-504999/504112_1_full.jpg

Dan T

[okc63avanti]

quote:Originally posted by Dan Timberlake

They have another product (Powertrax) for which they make this claim - " It combines the smooth operation of a limited-slip differential, with the traction performance of a locking differential." And feel it is the "ideal solution for just about any light truck, sport utility, and muscle car on the road today."


Dan T

Dan, Thanks ... I sent an e-mail to Richmond asking about the PowerTrax unit that their catalog says is for a Dana 44 19 spline application as to pricing, etc. I suspect it will be next week before I hear back from them as it is Good Friday today.

It sounds like its a lot easier to install (they say a DIY'fer can do it) where as the conversion with individual parts should only be done by a compotent axle/ differential shop.

John


63R-2386 under restoration & modification

[Dan Timberlake]

Hi John,
Why not rebuild and keep the TT/ limited slip?

The OEM chevy version positraction would burn one tire on asphalt with the other tire on gravel, at least once, on a light yellow 196X Sting Ray (not Stingray) roadster.

Dan T

[okc63avanti]

quote:Originally posted by Dan Timberlake

Hi John,
Why not rebuild and keep the TT/ limited slip?

The OEM chevy version positraction would burn one tire on asphalt with the other tire on gravel, at least once, on a light yellow 196X Sting Ray (not Stingray) roadster.

Dan T

Dan I'm a bit confused now. You suggested Richmond's PowerTrax and now you suggest keeping the TT/ limited slip. My rear end is currently all factory original and has the standard axle for an R1 with AC Avanti. It is a 3:31 ratio. The Avanti parts manual list part #1557407 for a standard 3:31 rear axle assy. The manual then list axle assy. numbers for "Twin Traction" differentials (Special Order) with the part #1557415 listed for a 3:73 ratio.

What I want to do is convert the ratio from 3:31 to 3:73 primarily because I am changing the trans from a PowerShift automatic to a Tremec TKO 5 speed. The 5th gear on the TKO has a ratio of 0.68 and at highway speeds that will drop the engine RPM just a tad too low. My thought was to not only change the ratio of the rear end but while I'm at it to convert it to Twin Traction or PosiTrac.

Are you suggesting this can be done with just the correct rebuild parts? If ordering the correct parts, and paying the expertise labor to assembly correctly is less expensive I'd go for that but if the Richmond unit is about the same and less labor than maybe its an option for me.

Has anyone ever seen the procedure for doing this conversion by rebuilding the rear end with correct parts and if so where can I get a copy of the procedure?

John


63R-2386 under restoration & modification

[sweetolbob]

John

Let me jump back in although I'm not an expert on Dana 44's.

AS long as you stay at 3:73 or lower ratio number, you should be able to just replace the ring and pinion because yours is in the lower threes. If you go to 3:92 or higher number that you need to change the carrier.

If you are happy with your posi than all you need is a gear change.

The gear set you get will be lapped in at the factory and will probably require more than just reassembly to get it correct. It will need shimming. You may be able to do it but, In spite of the fact that I've done several 8.5 GM units, I chose to have mine professionally done due to the lack of familiarity with these units.

I think the 19 and 30 spline units share the same gear split numbers.

The directions are all over the internet. Just Google Replace Dana 44 ring and pinion.

Hope this helps.

Bob

,

[okc63avanti]

quote:Originally posted by sweetolbob

John

Let me jump back in although I'm not an expert on Dana 44's.

AS long as you stay at 3:73 or lower ratio number, you should be able to just replace the ring and pinion because yours is in the lower threes. If you go to 3:92 or higher number that you need to change the carrier.

If you are happy with your posi than all you need is a gear change.

Hope this helps.

Bob

Bob, .... if I am happy with my posi? Sorry, if I so dense on this but with my Avanti differntial being a standard rear end does it mean it is limited slip or posi? The optional special order rear end for an Avanti was called Twin Traction in parts book.

I found a 3:73 dana 44 ring and pinion gear for $141 on the website you referenced but doesn't that just go in the standard differential and doesn't a Twin Traction have different internal parts?

What are the pro's and con's for the Studebaker Avanti standard differential vs. Twin Traction differential from a performance, cornering and handling stand point?

John


63R-2386 under restoration & modification

[sweetolbob]

John

Let me apologize for possibly misreading your post. I thought you had a limited slip (Twin Traction)

Let me digress. The difference between a standard rear end and any other type discussed here is reasonably simple. A standard rear end (or open rear end as it is also known) has no provision to transfer traction if one wheel slips. When the wheel starts to spin it will just keep spinning until you take your foot out off the accelerator or that wheel gains traction.

Any other type discussed here will transfer power to the non spinning
wheel. The method the rear end uses to transfer the power can be done by clutches, ratchets or cones and there in lies the different terminology. Posi, limited slip, ratchet etc, It is more complicated but will suffice for here.

So let me say

If you want a standard (open) rear end then all you need to do is change the ratio up to 3:73.

If you want the rear end to maximize power transfer (which would be my choice) you need to change the carrier to the special type that will transfer power between the wheels (posi, limited slip, etc.). Then the choice is only the type of traction control rear end.

Again if you are saying you could buy another axle with twin traction and change the gear ratio, that's one choice.

My choice would be to keep your rear end and upgrade to a newer style traction control like I did and change the gear ratio at the same time. You do the axles at the same time.

If I'm still in error just put it down to my advanced age and forgive the old.

Bob



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