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Pedal Smasher
1973 Opel GT
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Discussion Starter #1
The image below should provide plenty of information on the various special tools used when working on the differential. Not listed is the axle shaft puller J-8805 but a universal bolt-type wheel puller will likely work in place of this tool, as it has a similar design.

433264
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #2
It would be great if some of the critical dimension tools could be documented so they can be reproduced. J-22932 already has a better replacement, documented in the custom tools section.
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #3
I imagine the answer is yes to this question, but are these tools worth purchasing? I do plan on having the rear end rebuilt with a Quaife LSD in my GT. Is this something that can actually be done following the FSM, or do I pretty much need to send my rear end to Keith?
 

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Can Opeler
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3,421 Posts
I imagine the answer is yes to this question, but are these tools worth purchasing? I do plan on having the rear end rebuilt with a Quaife LSD in my GT. Is this something that can actually be done following the FSM, or do I pretty much need to send my rear end to Keith?
No special tools are required for disassembly. Aside from a bearing puller and a press. They would be helpful for assembly but not necessary. I dropped my rear end off at a local shop and they set it up with a fantastic tooth pattern for $300 in a couple hours. I provided the shims, bearings, 3 crush sleeves, and a print of the rear end section of the service manual.

The only special tool I saw him use was a dial to check runout on the ring gear. I have no noticeable rear end noise with my LSD aside from what is normal for my GT with a non isolated rear end (trailing arms have aluminum spacers and helm joints).
 
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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #5
Thanks for your input Kyler. I've been researching the tools and honestly, it wouldn't cost that much. Only some of the tools I can't find at this moment, which isn't bad. Looks like they used these tools a lot with GM vehicles, not just Opel. So, that helps with finding them. Even if I pay someone to do it for me, having all the tools helps them out but I think I'll try doing it with the FSM as my guide.
 

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Remember the early diff. is not the same as the later models and some of the tools are different. No need to buy something you would not use.

Keith has a Video for diff. overhaul that would be helpful to anyone doing this for the first time.
HTH
 
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Opel Key Master
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The key to reworking a differential and not needing several of the measuring tools, is to keep your ring gear and old pinion bearings with shims together. If you have the shims, you have the factory configuration. If you just have a rear gear set, then yes, you need the tools for measuring what your selective shims will be needed. Some of these rear tools you have to look through the manual for what you need, as they are not listed on the chart. The most expensive tool is a 1-15 inch lbs dial wrench I special ordered from Snap On. I had it 2 days after it was manufactured!
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #8
I'll be installing a Quaife, so that should avoid the early vs later diff issue. I do know the ring gear and the Quaife have to be machined a little to work together for the GT.
 

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Can Opeler
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3,421 Posts
I'll be installing a Quaife, so that should avoid the early vs later diff issue. I do know the ring gear and the Quaife have to be machined a little to work together for the GT.
You must have a later diff to install a Quaife unit. You can avoid machining if you get a 3.67:1 ring gear like I did for my ZF. You will need to redo all the shims if you install a LSD. The pinion should be reset too because they are pretty much all wrong from the factory from what I’ve read.

The 3.67 vs stock 3.44 ring gear makes very little difference. It’s worth the 6.7% Speedo error and loss of top speed. I think you can correct the speedo error with the correct speedometer/gear.
 
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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #10
Thanks for the info Kyler. I want to keep the 3.44 in the rear, it keeps the RPMs down. Is the rear end in a '73 late enough? Or are we talking later than '73?
 

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Can Opeler
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3,421 Posts
Thanks for the info Kyler. I want to keep the 3.44 in the rear, it keeps the RPMs down. Is the rear end in a '73 late enough? Or are we talking later than '73?
It only makes 250rpm difference at 75mph. It’s barely noticeable. Just means I have a tiny bit more passing power at 75mph:)

You just need to make sure a c-clip axle wasn’t swapped in. Most GTs after 71 have later axles.

However my 72 and 71 both had early axles swapped in which is why I had to buy a later one from OU...
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #12 (Edited)
I'll think about the 3.67 gear some more.

For the tools listed on the FSM page I posted, I have tracked down and purchased many of them the past 2 days. I still need to find J-21691-2, J-21691-4, J-21691-5, at least part of J-22938 (I have the screw and nut), J-22935, and possibly J-22588 although this does look like an ordinary bearing puller. I have sourced all the other components. So far, it cost roughly $300. It might not be necessary to do this, but if I want to rebuild it myself and put a Quaife LSD in, these tools will help me follow the FSM.

Later, I'll need to get bearings, crush sleeves, and the like. I'm not in a rush on this job, I actually should rebuild my 2.4 first but I want to get important and hard to find stuff so I don't have to worry about that later.

Oh, I do need to get an extra prop shaft so I can create J-22932.
 

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Pedal Smasher
1973 Opel GT
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Discussion Starter #13
I haven't purchased J-22912 yet and this looks like a regular bearing separator. You can buy it for like $100+ or HF sells a similar looking one for $30

 

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Atlantic City Pickers list these tools on eBay quite often but they think they are gold plated on pricing. IE: -4 gauge plate is almost three hundred dollars. I found one for $15. Shipping was more than the tool.
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #16
I managed to buy J-21691-6. I'm trying to buy J-21691-4, but the seller wants $300 for it. I'm hoping my offer of $100 will be enough. I've already bought a bunch of the other tools from this seller.
 

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Pedal Smasher
1973 Opel GT
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2,381 Posts
Discussion Starter #17
Atlantic City Pickers list these tools on eBay quite often but they think they are gold plated on pricing. IE: -4 gauge plate is almost three hundred dollars. I found one for $15. Shipping was more than the tool.
Did you buy all the tools, or just J-21691-4?
 

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Can Opeler
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3,421 Posts
I haven't purchased J-22912 yet and this looks like a regular bearing separator. You can buy it for like $100+ or HF sells a similar looking one for $30

The harbor freight bearing separator did not work on my axles. The ramp wasn’t steep enough. I end up using two pieces of angle iron in a press instead.
 
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Pedal Smasher
1973 Opel GT
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Discussion Starter #20
Do you still have a need for J-21691-4? Or some of the others I listed I still need?
 
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