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Manual Swap, LSD, LH 2.4?

2manyturbos said:
I agree with Redwood and culberro. The 3.31 was ridiculous gearing for most applications. The B23/B230 doesn't have enough torque to pull that tall gearing. On level ground you can use 5th gear above 60 mph. The 3.73 or 3.91 gear ration is perfect for a redblock. They like to run 2,800+ RPM.
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:nod:

It was something Volvo did to meet CAFE regulations, they had it right on the early cars until ~81.
 
What worked really well in a 240 was a 3.54 gear set. I converted a 1979 PRV automatic trans car to a B21F/M46 car and left the original rear axle. The car accelerated fine and ran great on the freeway. It would pull 30 mpg freeway driving it at 70 mph. It was literally the perfect compromise. 1982 B21F/M46 240s actually came with that gear ratio.
 
^^ That's why it is purely opinion based determined by the conditions the car is normally operated under. For freeway driving, the 3.31s with an M47 are great. My Classic wagon would pull 31 mpg while driving on the freeway at 70 mph. My LS1 Z28 pulls 70 at something like 1,200 RPM. It sounds like a diesel truck in 6th gear. It has immense torque though.
 
The Magic Numbers.

2manyturbos said:
What worked really well in a 240 was a 3.54 gear set. I converted a 1979 PRV automatic trans car to a B21F/M46 car and left the original rear axle. The car accelerated fine and ran great on the freeway. It would pull 30 mpg freeway driving it at 70 mph. It was literally the perfect compromise. 1982 B21F/M46 240s actually came with that gear ratio.
Click to expand...

:nod:

Makes 1st gear useable and if you shift out at 2500 and run at 2500 you'll get great fuel economy for a 240.
 
Wow, thanks for the amount of experienced based information!

Sounds like my current axle is adequate for a manual transmission for now. If I end up wanting a lower numerical gear set in the future, I'm comfortable building a differential up with the 3.54 and I could do a TruTrac at the same time. My exhaust is magnaflow in place of the rear muffler, with the factory pre muffler still in place. If it's too loud, I'll put the stock muffler back in. :nod:

An M46 sounds like the easiest, least invasive option. I'm wondering where the cutoff is as far as mileage on those? If synchros and other wearing parts are NLA or rare, I'd better be pretty careful in what I end up putting my money towards.

My B23F is the lower comp version, as those were on the standard cars, so maybe a bit more "squish" wouldn't be a bad idea. And, yeah, it's LH 2.0. Works well! It has an A cam advanced 4 degrees. Worlds better than an M cam, but I just don't think the autos get the B23s in the RPM range they like to be at.
 
These low compression motors don't make a ton of exhaust noise in the first place. It's more important to pipe it out the back of the car than to have xxx mufflers in place.

I'm doing a short cherry bomb in the middle and a longer cherry bomb in the rear, but it will be piped all the way out past the bumper. Any exhaust that dumps under the car will be too loud.
 
Also, shaving the head a mm is always safe in a redblock, using stock cams. Many people have done more than 1mm, and/or some people do high lift cams plus 1mm shave and they are fine. The stock block/head combo has a lot of headspace.
 
HiSPL said:
These low compression motors don't make a ton of exhaust noise in the first place. It's more important to pipe it out the back of the car than to have xxx mufflers in place.

I'm doing a short cherry bomb in the middle and a longer cherry bomb in the rear, but it will be piped all the way out past the bumper. Any exhaust that dumps under the car will be too loud.
Click to expand...

HiSPL said:
Also, shaving the head a mm is always safe in a redblock, using stock cams. Many people have done more than 1mm, and/or some people do high lift cams plus 1mm shave and they are fine. The stock block/head combo has a lot of headspace.
Click to expand...

Okay, chances are it won't be awfully loud then.

Interesting. I've seen people say that it's worth the bump in compression on this forum. I'll give that more research and thought
 
If it is a 1031 diff it will fit, If it is a 1030 it will not, check to be sure.
 
My diff has the two ribs on the driver side, looks to have the protruding bump on the top. No cooling fins on the bottom. That's an older 1031, correct?
 
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So I've been looking at the gearing of a Ford T5, it has a first ratio of 3,35:1. The M46 has a first of 4,03:1. So with a rear end ratio of 3,91:1, the M46 first gear is not all that great. But with the T5 it would actually be a better match, correct?

I'm feeling a bit hesitant at the idea of an M46 or M47 after the issue I was having finding springs for my car. The T5 will have support for the foreseeable future, and so I'm wondering if a T5 swap might actually be the best choice at this point... Plus not having to mess with my rear end for now would be nice!
 
There is a 2.95 first gear T5 out there. Or buy the gear set and install it.

With a shorter rear gear the 2.95 makes first gear actually usable.
 
OldCarNewTricks said:
So I've been looking at the gearing of a Ford T5, it has a first ratio of 3,35:1. The M46 has a first of 4,03:1. So with a rear end ratio of 3,91:1, the M46 first gear is not all that great. But with the T5 it would actually be a better match, correct?

I'm feeling a bit hesitant at the idea of an M46 or M47 after the issue I was having finding springs for my car. The T5 will have support for the foreseeable future, and so I'm wondering if a T5 swap might actually be the best choice at this point... Plus not having to mess with my rear end for now would be nice!
Click to expand...

You can keep the 3.9 rear end with a m46/m47, the 0.8 5th gear in the m46/47 is actually really nice with a lower geared diff. That is unless you're spending hours on the freeway.

The low 1st gear in the m46/47 isn't great with a low ratio diff, but 2-5th are much better matched for fun driving. I like the low ratio 1st, especially in stop-n-go traffic. You can just let the car idle along.

There are a few issues with t5s that you will run into:
1) Good luck finding a good usable one for cheap. Cheap ones almost always need a full rebuild and you might as well buy a new T5z at that point. Gear kit and bearing kit will run you close to $800 for the cheap parts, plus labor. A new T5z is ~$1800.
2) They make a lot of noise and can be a pain to get all the driveline vibrations minimized.
 
culberro, you bring up an excellent point, which is the driveline vibrations. With adapters, and a non OE driveshaft, I expect I would personally find that torturous. My truck has a bent axle flange that I still need to fix, and it's awful.

I don't intend to drive the 242 on the freeway for extended trips. At most, I'll be going to camping spots, beach etc. But the gearing will come in handy then, I think.

Alright, I'll go with a Volvo trans. I've been looking around, and at the PnP, I don't see pre 86 240s all that often. Is it easier to find M47s nowadays? I was also looking at the GPS speedo boxes, and I'm not sure how those would hook up to the Volvo cable.

Anyone know the best place to look for an M46?
 
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