My E24 LSD Differential Proximity to the Muffler

[Catbert]

It's fun to learn new things about my car from the posts I have posted so far. One topic often bleeds into another... a good thing. In one of my posts about the dreaded Allen key oil drain and fill plugs or perhaps the one about whether I have a LSD, one member commented about my comment on how the upper fill plug of my E24 diffy sits 1mm from the muffler. He said my exhaust configuration wasn't right. Well, I have seen numerous E9s with a muffler sitting just as mine is, but likely not paired with an E24 diffy.

I've been buying stainless steel oil drain and fill plugs to replace those dagnabit Allen plugs which strip easily and are often near impossible to remove when they haven't been touched in years. My car was recently acquired one month ago, so that is what I am dealing with. My muffler was hammered by someone before me to create space for the E24 diffy installation. Still, the gap was far too close to avoid muffler heat from heating the diffy oil... a bad thing. The first stainless hex head fill plug sat 1 or 2mm higher, so that only made the problem worse. Then, I bought a stainless Allen plug but it did't thread flush or near flush on the diffy. So, I tried to hammer the muffler a bit more and only made a small difference. Those two-wall thick mufflers are quite strong. I was able to create about a 5mm gap from my hammering and then came up with an idea to use thermal sheathing I had on hand to wrap the muffler where the plug is on the diffy. That should help a bit.

 

[Ohmess]

That flat spot on the side of your diff should have stamped numbers on it that indicate the gear ratio. For e9 diffs, you should expect to see 39/12, 38/11 or 40/11. (Note the slashes will not be present.)

 

[Catbert]

That flat spot on the side of your diff should have stamped numbers on it that indicate the gear ratio. For e9 diffs, you should expect to see 39/12, 38/11 or 40/11. (Note the slashes will not be present.)

@e9Leveque commented on another post that the E24 diffy has a different numbering scheme. For example, the 33:11 numbers I found at the very top don't equate to having a 3.0 gear ratio. He said it was the housing part number. I intend to use the wheel rotation technique to count wheel and driveshaft rotations to then determine the true ratio.

 

[e9Leveque]

Yes but @Ohmess is correct that the ratio SHOULD be stamped there. It may be hard to see so the wheel revolution method is likely your route forward

 

[sfdon]

The numbers are behind the flange on passenger side on that late 3.07 sideloader.

 

[Catbert]

The numbers are behind the flange on passenger side on that late 3.07 sideloader.

Not on mine... unfortunately. Yes, I cleaned it but it was already free of any heavy grease, grime, and road dirt. BUT... I will look once again today when I do the wheel/drive shaft rotation method.

 

[ElGrecko]

There's stainless steel and then there's stainless steel. Typical grades like 304 are soft, gall horribly and are a general PITA they have a yield strength of around 35ksi and are pretty much worthless. Others like 17-4 and 15-5 and A286 are fine. The point being that "stainless steel" isn't necessarily the "good stuff" and be careful what you use. The zip ties on that wrap most likely aren't a good idea. Insulation doesn't stop heat transfer, it only slows it down and if the heat isn't being taken away things get hot anyway. The area at the top of the muffler isn't getting much air circulation and plastic isn't going to be very happy there. Ther wrap is fine, but get some muffler metal zip ties (that are generally made of stainless BTW) and that will keep your

 

[Catbert]

I have resolution on my diffy gear ratio. First, here is a photo of the area @sfdon said the ratio number would be on my E24 diffy. It seems mine is an anomoly. A2 86 ain't the right numbers. Soooooo... I marked the rear wheel and drive shaft and performed the rotation method. I came up with 3.11 rotations. Sooooo... mine is a 3.07, common with the E24 diffy as some have said. Peace.

 

[e9Leveque]

Glad you got resolution on this and a nice writeup for the rest of us on how to find the gear ratio by using wheel rotation. Any idea why someone went with an E24 diff rather than sticking with one of the more typical E9 options? I'm going to guess availability but seems a bit odd to have gone for a lower ratio when most of the discussion is often about increasing the ratio when adding a 5-speed transmission either OD or CR

 

[Catbert]

Glad you got resolution on this and a nice writeup for the rest of us on how to find the gear ratio by using wheel rotation. Any idea why someone went with an E24 diff rather than sticking with one of the more typical E9 options? I'm going to guess availability but seems a bit odd to have gone for a lower ratio when most of the discussion is often about increasing the ratio when adding a 5-speed transmission either OD or CR

Good question, but academic. Some people just don't make good decisions. At least I have a Getrag 5-speed and a newer diffy which @sfdon said is beneficial. I'll just be accelerating from a stop like grandma Moses and not burning rubber.