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  #16  
Old 03-05-2005, 12:44 AM
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I am thinking of salvage yard hunting this weekend. Can you tell me how I can tell what ratio the rear end is?

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  #17  
Old 03-05-2005, 12:56 AM
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Quote:
Originally Posted by brabus
I am thinking of salvage yard hunting this weekend. Can you tell me how I can tell what ratio the rear end is?
From what I understand, there is a stamp on the case that provides the ratio. Haven't checked it personally.

You can always verify it by rotation of the axle.

Hold one axle flange, or wheel, stationary.

Turn the other wheel 10 full revolutions and watch the drive shaft or the input flange.

Count the rotations of the drive shaft or input flange. Divide the rotations of the drive shaft, or input flange by 20. That's your ratio.
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  #18  
Old 03-05-2005, 12:23 PM
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Quote:
Originally Posted by Brian Carlton
Randy, is this with an automatic?
Also, what size tires?
I'd like to compare the calculated engine speed with the actual speed to get a figure on the slip (presuming automatic).

Lilly is a box stock '84 300D (auto), 3.07:1 final drive ratio and Michelin X-One P195-R7014 tires.

I have a 2:88 pumpkin in the garage that I was planning to put into Marlene but, Lilly needs a pair of axles and I'm seriously contemplating the installation of the 2:88 at the same time as those axles go in...there's another 2:88 in Passion Flower I can stick in Marlene but, I'd actually like to find a 2:65 from a W124 (if it would fit) or a 2:47.
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  #19  
Old 03-05-2005, 01:42 PM
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Quote:
Originally Posted by R Leo
Lilly is a box stock '84 300D (auto), 3.07:1 final drive ratio and Michelin X-One P195-R7014 tires.
Thanks.

The calculated engine speed for that combination at 75 mph is 3132 rpm.

The actual engine speed, confirmed with GPS at 75 mph is 3350 rpm.

So the slip in the automatic is 218 rpm's in this specific case.

This is valuable data for the future and is useful to predict the rpm of the engine, equipped with an automatic, at a given road speed.
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  #20  
Old 03-05-2005, 11:13 PM
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Lilly's new rear end...

Lilly ('84 300D) needed axles badly and, I had a 2:88 diffy in the shop; I couldn't help it, things just happened. I can't wait to run her tomorrow and see what she's like with the taller gears.

I took pics too...will post some tomorrow.
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  #21  
Old 03-05-2005, 11:30 PM
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My 84 300D turns 3350-3400rpm at 75rpm with 205/70-14's just like RLeo's. I just won a 2.88 diff and I can't wait to see how big a difference it makes. I would think a 3.07 diff would be a good choice for a 300D NA for highway use. RT
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  #22  
Old 03-06-2005, 12:24 AM
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Quote:
Originally Posted by rwthomas1
My 84 300D turns 3350-3400rpm at 75rpm with 205/70-14's just like RLeo's. I just won a 2.88 diff and I can't wait to see how big a difference it makes. I would think a 3.07 diff would be a good choice for a 300D NA for highway use. RT
Interesting I started this post because I was getting ready to pull the trigger on that auction! http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7957876995
You can thank Brian for convincing me to back off and not bid it up on you! The seller seems to be a bit daffy. I asked him the shipping cost to my zip and he quoted me prices based on a shipping weight of 20lbs. I'm sure it must weight at least 3 times that. I hope you get it OK.
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  #23  
Old 03-06-2005, 12:40 AM
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Quote:
Originally Posted by rwthomas1
My 84 300D turns 3350-3400rpm at 75rpm with 205/70-14's just like RLeo's. I just won a 2.88 diff and I can't wait to see how big a difference it makes. I would think a 3.07 diff would be a good choice for a 300D NA for highway use. RT
Bill, that 3.07 that RWT has might be an acceptable compromise for the n/a engine. One step down from the 3.46, but not as radical as the 2.88.

He'd probably sell it to you cheap!
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  #24  
Old 03-07-2005, 08:50 AM
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I've completed the 3.07 to 2.88 swap in Lilly and I have to say at cruise, a 6% reduction in RPM doesn't really turn out to be all that much. On the plus side, there's no noticeable loss of performance on acceleration.

This particular swap probably isn't worth the effort, IMHO.

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