Rear Axle: Twin Traction installation

[c locke]

Hello all,
I have a complete set of rear end gears for my little half ton truck. And, wonder of wonders, it includes a twin traction differential. I have all the books for my truck ('51 2R5) and understand the installation process of the ring and pinion very well. I also have (almost) all the tools necessary, however, I'd like to ask those of you out there who know the TT unit (as I don't) is the installation requirements the same? Obviously the TT didn't exist in '51, and I don't have a later book that provides the instructions (Dana 44). Does someone out there have a set of instructions they could photo copy or point me in a direction? Compared to modern day setup instructions, the Stude book is very simple. Very few measurements - .008" pre-load on the ring gear bearings, 0 travel and slight drag on the pinion, .003" backlash on the back of the ring, etc.

The "almost" i mentioned above is for the tool that sets the depth of the pinion from the rear face of the pumpkin. I don't have that one, so will be making a jig shortly to make a comparison measurement on the existing gears. Speaking of the existing gears...

The set I bought is a 3.73. The gears ordered with the truck were the option 4.89 with the T-9 4 speed transmission. I wrote a spreadsheet calculator that gave me the various speeds for a couple RPM's, and it appears that 2nd with the 3.73 will be extremely close to 3rd with the 4.89. ANd the difference between 3rd and 4th is .59, which is really close to OD (I think normal there is .7) So, there will be some shifting on hills, but on places where I can do 45 it won't sound like the engine is going to come out from under the hood!

By all means, if anybody has any comments or suggestions, please feel free to offer them. I'm by no means an expert on these trucks, but i am a good mechanic and engineer, and think I have a good sense of logic and common sense, and i'm not offensive when it comes to criticism. Looking forward to any replies! thank you all
chris

[sweetolbob]

Go to the Spicer/Dana web site and you will find the complete directions/manual on rebuilding/installing in to the 44. The pinion depth method they use, as you suspect, can be done several ways. I used a standard dial indicator on mine. Same with the case spreader. I would suggest you also take the old bearings and open them up enough to slide on the shafts so you don't need to press them on and off each time you add/remove shims. That's also in the Dana manual.

Just take your time and think about what/why you are doing as you stated above. It all makes sense and you'll do just fine.

Bob

P.S. If you can't find it, PM me, I have a copy in PDF but it will take some hunting in my Win 8.1 byte bucket.

[studegary]

Is it safe to assume that your pickup already has a 44 differential?
I thought that there was some cutoff range of low ratios where the gear sets were not interchangeable with the high ratio sets. A 4.89:1 is certainly a low ratio. Check this out before proceeding.

[Skip Lackie]

I believe Gary is correct. I don't believe the 3.73 ring and pinion will fit in a carrier originally designed for 4.89. There were differences between the carriers used for 3.73 and below (numerically) and 4.09 and above.

[bezhawk]

Actually the 3.73 was the cut off point for gearing. Anything below that requires a different carrier. He will be fine.

[sweetolbob]

I'm with Skip here 3.73 and down (numerically) - 3.92 and up (numerically) is the split. 30 and 35's split at 3.54

http://www.differentials.com/technical-help/carrier-breaks

Bob

[bezhawk]

I'm with Skip here 3.73 and down (numerically) - 3.92 and up (numerically) is the split. 30 and 35's split at 3.54

http://www.differentials.com/technical-help/carrier-breaks

Bob

I stand corrected, Actually, I'm sitting Good info. The info posted to most sites is confusing, and they usually don't post visual clarification like you just did.

[sweetolbob]

I stand corrected, Actually, I'm sitting Good info. The info posted to most sites is confusing, and they usually don't post visual clarification like you just did.

Just didn't want to see the OP get surprised but continued thanks from here for being the resource you are.

Bob

[c locke]

I think the cutoff was 3.90, but either way, i have the whole shebang: ring, pinion, bearings, cups, carrier, TT diff, truss blocks, shims, you name it. I'm eager to put it in. I'll go to the dana website to look up the setup, as i'm hoping they have some real measurements using calipers rather than that funny offset thing... The truck was stock supplied with the spicer 41 4.82, but my wife's grandfather ordered this with the optional 4.89, so it came with the 44 rear end. Doing some reading on the 2R truck registry, now i'm hoping that the axle splines line up since the gear set is newer than my truck.. i'll keep my fingers crossed. THanks all!

[Skip Lackie]

I'm with Skip here 3.73 and down (numerically) - 3.92 and up (numerically) is the split. 30 and 35's split at 3.54

http://www.differentials.com/technical-help/carrier-breaks

Bob

Thanks Bob (not for agreeing with me -- but for posting the link to that site!).

[c locke]

Boy that's a great site, thanks Bob! Why is it when you go*gle search something sites like that don't come up? OH well, i'm eager for snow to fall so i can get started on my new project. I have another question about speedometer adapters, but i think i'll start a new thread... thanks all very much for your help!
chris