[Chris65LeMans]

I have an M21 in my car that was behind a (now blown up) 96 headed 400. I've got 3.73 rear gears.

I think the M21 is great for my street cruising, but it needs lower rear gears. If you run it with 3.08 or 3.31, you'll find the bigger 1st gear makes taking off a bit tougher. When I bought my car, it had 3.31s, and would lug considerably in stop and go traffic. the switch to 3.73s really woke things up.

[JLMounce]

I agree that if you're set on going with a 4 spd (I'd still go 5 spd considering you're changing from auto) I'd go with the m23z.

The m23z gearset with a 3.08 or 3.23 has a really nice gear spread that gives you a good starting line ratio and allows the big poncho's torque to carry the car nicely through the rest of it's forward gears. The tall rear ratio keeps you more relaxed at highway speeds.

I almost went this direction, but by the time I got the trans, swapped gears, installed everything needed for the swap from auto to manual, I was within about 800 bucks of a TKO swap. Couldn't justify it.

[Formulajones]

Originally Posted by JLMounce

I agree that if you're set on going with a 4 spd (I'd still go 5 spd considering you're changing from auto) I'd go with the m23z.

The m23z gearset with a 3.08 or 3.23 has a really nice gear spread that gives you a good starting line ratio and allows the big poncho's torque to carry the car nicely through the rest of it's forward gears. The tall rear ratio keeps you more relaxed at highway speeds.

I almost went this direction, but by the time I got the trans, swapped gears, installed everything needed for the swap from auto to manual, I was within about 800 bucks of a TKO swap. Couldn't justify it.

Yep, I've been preaching that for a long time but I don't think people comprehend it until they actually dive in and get the job done, then look at the total bill LOL

Now that I re-read the OP's 1st post I'm in total agreement. If switching from an auto to a manual and having to do the full conversion, I retract my statement of using the M-20 for his rear gear change. I thought he was simply wanting a rear gear change and was running the M-21. So in that case, absolutely just spend the money and do a 5 speed swap, you won't regret it.

[JLMounce]

Originally Posted by Formulajones

Yep, I've been preaching that for a long time but I don't think people comprehend it until they actually dive in and get the job done, then look at the total bill LOL

Now that I re-read the OP's 1st post I'm in total agreement. If switching from an auto to a manual and having to do the full conversion, I retract my statement of using the M-20 for his rear gear change. I thought he was simply wanting a rear gear change and was running the M-21. So in that case, absolutely just spend the money and do a 5 speed swap, you won't regret it.

If the car is already a 4 speed, and you already have a case, and your rear ratio is already in the 3.08 to 3.31 range, you can just get the gearset. It's an economical way to get 90% of the way to the performance and highway driving ease of a 5 speed.

The more you have to change from that equation, the better the 5 speed swap starts looking.

ESPECIALLY now that the slim case TKX is out and you don't have to worry about cutting the tunnel. For the bit extra, it just makes sense to go all the way.

[Formulajones]

Originally Posted by JLMounce

If the car is already a 4 speed, and you already have a case, and your rear ratio is already in the 3.08 to 3.31 range, you can just get the gearset. It's an economical way to get 90% of the way to the performance and highway driving ease of a 5 speed.

The more you have to change from that equation, the better the 5 speed swap starts looking.

ESPECIALLY now that the slim case TKX is out and you don't have to worry about cutting the tunnel. For the bit extra, it just makes sense to go all the way.

I'm not much into sinking money in the 4 speeds anymore. Used to do that 30 years ago when you could still buy a muncie for $100 but these days, If I'm dealing with a 4 speed that needs something, unless it's a numbers deal and it needs to be there, I just go right for the 5 speed swap and never look back. I look at it as a chance to upgrade and turn the car into a more pleasurable driving experience.

[gobrdgo]

I bought a Doug Nash five speed. Currently refurbishing the 69 original 4 speed pedals I scored here. Whomever said it would be an expensive swap wasn’t kidding. But I’m having fun.