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change long differential to short


HenryC
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I have a l969 1600 with a l972 2000 engine. I want to convert the 4.11 long differential to a later model 3.64 short differential. I have acquired the rear crossmember, driveshaft, diff., trailing arms with stub axles. and axles with CV joints. I am not a mechanic and need to know the step by step procedure to remove old assembly and install the new assembly. There is probably a thread, but I cannot locate it. If someone could direct me in that direction, I would appreciate it. Also, do I need any other parts? Thanks in advance for any help. HenryC

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Coupla things you didn't mention:

1. Your 1600 has smaller rear brakes than the 2002; are you also installing the 2002 brakes you presumably got with the rest of the rear axle assy?

2. IIRC your 1600 used a 6 bolt guibo (not the same as the one on the automatics or used in a 5 speed conversion), so do you have a proper 4 bolt spider for the tailshaft of your 1600 tranny? If you used the 2002 tranny along with the engine, this shouldn't be a problem.

With these problems solved...

Basically, then you

1. unbolt the old driveshaft and remove it

2. disconnect the hydraulic brake hoses at the rear crossmember (a good time to install new hoses if yours are original)

3. disconnect the emergency brake cables

4. support the diff/crossmember with a trolly jack and unbolt the assy from the body, and lower it.

Install the new stuff in reverse order. Lots of niggly details, such as guibo bolt placement, pre-loading the center support bearing etc. Check archives or the factory manual for all the details.

cheers

mike

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Coupla things you didn't mention:

1. Your 1600 has smaller rear brakes than the 2002; are you also installing the 2002 brakes you presumably got with the rest of the rear axle assy?

2. IIRC your 1600 used a 6 bolt guibo (not the same as the one on the automatics or used in a 5 speed conversion), so do you have a proper 4 bolt spider for the tailshaft of your 1600 tranny? If you used the 2002 tranny along with the engine, this shouldn't be a problem.

With these problems solved...

Basically, then you

1. unbolt the old driveshaft and remove it

2. disconnect the hydraulic brake hoses at the rear crossmember (a good time to install new hoses if yours are original)

3. disconnect the emergency brake cables

4. support the diff/crossmember with a trolly jack and unbolt the assy from the body, and lower it.

Install the new stuff in reverse order. Lots of niggly details, such as guibo bolt placement, pre-loading the center support bearing etc. Check archives or the factory manual for all the details.

cheers

mike

Disconnect the rear shocks and remove the rear springs, also.

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I do have the 2002 transmission as it has the 4 bolt connection to go with the replacement driveshaft. I suspected it was a 2002 transmission because the speedometer registers much, much higher than the actual speed of the car. The speedometer gear in the transmission does not go with the 4.11 differential gearing. I did not get the bigger brake assemblies with the parts I gathered. I thought I would just use the smaller brakes that seem to work well.

Can I just move the brake assemblies aside and not disconnect the hydraulic lines? I appreciate very much your help.

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You'll have to pull the brake lines- they run up the trailing arms.

But that's no big deal, as it's time to change all your rubber brake lines anyway. Might be time to think about brake upgrades if you have the

small front calipers, too.

Honestly, if it was me at this point, I'd put the vented rotors/volvo calipers

and 320 rear drums on it. It's a very cheap way to put as much brake

as you'll ever need on the car, and for me, they've been bulletproof.

I'd have a set of parking brake cables on hand- they're easy to change,

and they do stretch...

Be careful releasing tension on the rear springs-

a jack under the trailing arm works fine, but you need to unhook

the rear cv joint at the outside end to do that, as the cv won't droop

far enough to release the spring.

The subframe can fall off the bolts- or it can be a real bugger. I've had them

go both ways. A jack under the diff helps a lot, as you can use that to

adjust the angle of the subframe as it comes down.

Other times the rubber mounts have disintegrated- makes it easy.

hth

t

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I'm old and not as fast with everything any more. In the long run, I'd like to change over to a 5 speed, but I thought I would start with this. I will order new brake lines as you suggested. Perhaps I should follow your advice on bigger, newer front and rear brakes as a next step before the 5 speed swap. It took me months just to find the replacement differential and parts here in East Tennessee.

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