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Old 07-31-2022, 01:27 PM   #1
spock345
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Default T5 in an pushrod car

This post is mostly going to be my musings on modern five speeds in pre 1975 cars. So I will be rambling a bit. Given the rarity of M41 gearboxes (I am now seeing prices of $2500 in some places for a rebuilt unit) I've been trying to think of a way to get a T5 into a push rod car with minimal effort. So I'd like to minimize cutting, welding, and custom fabrication. I think I have figured out a formula that would make it work. That said it'll probably be more pricey than they old T5 out of a fox body approach.

My car was originally an automatic, so it already has a wide transmission tunnel. So no need for a new tunnel there. The annoying bit is the shifter. I'd like to retain stock-ish shifter placement. A few inches back would be fine. This would mean a T5 out of a truck (S10s come to mind). So a bit of hammering and a new hole, and some shopping for the right shift lever, no problem. Then we come to the driveshaft.

One tricky bit I've been trying to figure out is the drive shaft. Most T5s have a slip yoke and I know that driveshaft shops don't like putting two slip yokes on the front driveshaft half. Also I'd like to keep the stock setup and not navigate trying to get a one piece through that weird hole in the body. Although the infinite variation of the T5 has delivered a solution in the gearbox from an S197 4.0L mustang which has a flange to bolt up to. I have noticed the gear ratios aren't the best, 3.75:1 1st and a 0.73:1 OD. So seems like if you were to somehow bolt a D type overdrive up to an M46. The S197 T5 weighs 75lbs dry versus an M41 at 90lbs. So you save some weight.



I guess that just leaves getting the gearing and input shaft right, which as I understand it isn't too hard with these gearboxes if you have cash to throw at it.

So I guess what I am envisioning is the following.
  1. Starting with a 140 or Amazon with either the wider tunnel or do some cutting, hammering, or welding.
  2. Move the shifter hole a few inches back (nothing I've found is quite far forward enough to match the M40/41 except for a TKO).
  3. Modify the S197 T5 with the right input shaft for a red block per documented swaps.
  4. Figure out the transmission cross member (again decently well documented for BW35->M40 swaps in Amazons).
  5. Shorten an M40 front driveshaft half and attach the right flange for the T5.

Sorry for the rant, this has been rattling through my head and I wanted to share and see what other folks think of the idea. Definitely not the cheapest way to go.
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Old 07-31-2022, 02:12 PM   #2
gsellstr
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For the driveshaft swap, since you want to stay 2pc, take a look at the Spicer center bearing that's floating around, forget the part number now, but VB242 did a post on it a while back, several others including myself went that route. It has plenty of strength to keep the shaft located allowing the use of 2 slip joints. Not ideal, but an option. Also, looking at that flange on the trans you pictured, is there clearance in the tunnel for something that large?

I can't help much more than that since I'm basically working with a 240 tunnel in mine.
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Old 07-31-2022, 02:48 PM   #3
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Quote:
Originally Posted by gsellstr View Post
Also, looking at that flange on the trans you pictured, is there clearance in the tunnel for something that large?
I can't imagine it'll cause a problem considering that it can't be much wider than a J type OD, which fits just fine.
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Old 08-06-2022, 03:42 AM   #4
Andy Somogyi
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What about making a 2-piece driveshaft that removes the slip yoke on the tail side and keeps the slip yoke on the t5 trans side?

Basically just weld up the Volvo slip yoke.
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Old 08-08-2022, 01:43 PM   #5
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The innards shouldnt be much different with that short gearbox vs a different gear set. So you could have that box built with a cluster and gear set out of a 3.15 or 2.95. But you may not be able to change 5th gear ratios. Worth talking to someone like AMP Distributing.

Also may want to consider bellhousing options in the thought processes. The adapters available now will not fit an M40/41 Bellhousing, so have to use the m46 and whatnot to get that working. Soon ish, I will have an M41>T5 adapter, 3.15/0.72 T5 available (dang close to M41 ratios but better handling of power), but the gearbox will need a rebuild, 2nd gear slider and new mainshaft.
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Old 08-08-2022, 10:11 PM   #6
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Quote:
Originally Posted by cwdodson88 View Post
The innards shouldnt be much different with that short gearbox vs a different gear set. So you could have that box built with a cluster and gear set out of a 3.15 or 2.95. But you may not be able to change 5th gear ratios. Worth talking to someone like AMP Distributing.

Also may want to consider bellhousing options in the thought processes. The adapters available now will not fit an M40/41 Bellhousing, so have to use the m46 and whatnot to get that working. Soon ish, I will have an M41>T5 adapter, 3.15/0.72 T5 available (dang close to M41 ratios but better handling of power), but the gearbox will need a rebuild, 2nd gear slider and new mainshaft.
I know a few folks make adapters for the M40/41 housings. There is the notorious VPD but apparently Tinus Tuning also makes one.
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Old Yesterday, 12:05 AM   #7
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Quote:
Originally Posted by Andy Somogyi View Post
What about making a 2-piece driveshaft that removes the slip yoke on the tail side and keeps the slip yoke on the t5 trans side?

Basically just weld up the Volvo slip yoke.
I've been thinking about that. I am just trying to figure out how to pull it off while maintaining the stock center carrier bearing. The bearing is on the front half and the rear half slips into the front half. I think the idea behind having that slip joint there is so that as the rear axle moves any slight differences in effective driveline length is accounted for.

So two slip yokes would give you a "floating" front half. Not the worst but I can see wanting to have at least one end firmly attached to something and let the rubber center carrier bushing take up any movement or vibration. Removing the slip yoke from the rear half would take away that length flexibility and increase strain on the center bearing. If I understand it correctly.

Really my mantra so far has been the closer to a stock configuration the better.

Last edited by spock345; Yesterday at 12:13 AM..
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