3 speed manual to 5 speed manual conversion

[Ken71Twister]

My ‘71 Duster is currently being restored by a semi-local restoration shop with a solid reputation. I just took my 318 engine to a shop in Mobile AL for a rebuild and I’m now looking at my 3-speed manual transmission. The restoration shop owner says that he’s not finding anyone enthusiastic about going thru the inspection and repair process on my 3-speed. The idea was presented that I convert to a new 5 speed transmission. The idea is tempting but I don’t know which brands I should be looking at. Any suggestions and thoughts on the 3 speed to 5 speed conversion?

FYI - The car has a 3.91 rear end and I’m hoping that the 5 speed transmission would offer an overdrive to reduce highway RPM.

 

[Garrett Ellison]

Is it an A230 floor shift or a 250 column shift? If it's a floor shift car, just find an A body four speed to put in it.

 

[darndart]

Silver Sport Transmission and American Powertrain both have nice kits for the conversion. Neither one is a bolt in deal, and requires floor pan and crossmember surgery. Passon Performance A855, is the only one that offers a direct bolt in, no cutting required 5-speed overdrive.

 

[Professor Fate]

Any 5 speed conversion is going to require substantial surgery (except the Passon, and good luck getting one of those anytime this decade).
Which brings up the thought: if they're so hesitant to do a simple refresh on a 3 speed, I sure as hell wouldn't trust them doing the kind of mods a 5 speed conversion would entail. Just sayin'.

 

[RustyRatRod]

Let's stop and think about this. If the shop doesn't have the know how to inspect and repair a simple 3 speed manual transmission, what makes you think they're capable of any of the rest? I believe you need to think on that question REAL HARD.

 

[Ken71Twister]

Is it an A230 floor shift or a 250 column shift? If it's a floor shift car, just find an A body four speed to put in it.

It is a floor shift.

 

[DumpsterFire]

Any 5 speed conversion is going to require substantial surgery (except the Passon, and good luck getting one of those anytime this decade).
Which brings up the thought: if they're so hesitant to do a simple refresh on a 3 speed, I sure as hell wouldn't trust them doing the kind of mods a 5 speed conversion would entail. Just sayin'.

I can kinda see it. I'm way more comfortable fabbing up mounts and making room for new tranny than going through one I'm unfamiliar with

 

[Professor Fate]

I can kinda see it. I'm way more comfortable fabbing up mounts and making room for new tranny than going through one I'm unfamiliar with

Not a chance. This is supposed to be "a semi-local restoration shop with a solid reputation". OP is paying the freight and the shop does the work. Their preferences don't matter- their job is to give the customer what he wants. If they're not willing to do that, then you take your business down the road to a place that will give you what you want.
An actual "restoration shop" wouldn't blink twice at a three speed. Do you think anybody is "familiar" with a 1937 LaSalle three speed? Not me, but I did one anyway for a friend's flathead... Think I'm familiar with or even like Hyundais? No, but I fix my DIL's regularly.
They're just trying to oversell the OP and take more of his hard-earned money. And they even said "he’s not finding anyone enthusiastic about going thru the inspection and repair process on my 3-speed", which means they're not even doing the work themselves, they're farming it out... Some resto shop. Take your business elsewhere.
OP, if you're happy with the way your 3 speed drives with your 318, but would like an overdrive; then just get an 833 OD transmission and A/F body bellhousing. It amounts to a three speed plus overdrive, and it all bolts in. No mods to the floor or crossmember, same clutch/flywheel/pressure plate, same linkage. No cutting, welding or fabbing parts, no goofy unobtainable service parts. It's even the same length driveshaft. The only difference (depending on the version you get) MAY be the front slip yoke. Done.

 

[RustyRatRod]

Not a chance. This is supposed to be "a semi-local restoration shop with a solid reputation". OP is paying the freight and the shop does the work. Their preferences don't matter- their job is to give the customer what he wants. If they're not willing to do that, then you take your business down the road to a place that will give you what you want.
An actual "restoration shop" wouldn't blink twice at a three speed. Do you think anybody is "familiar" with a 1937 LaSalle three speed? Not me, but I did one anyway for a friend's flathead... Think I'm familiar with or even like Hyundais? No, but I fix my DIL's regularly.
They're just trying to oversell the OP and take more of his hard-earned money. And they even said "he’s not finding anyone enthusiastic about going thru the inspection and repair process on my 3-speed", which means they're not even doing the work themselves, they're farming it out... Some resto shop. Take your business elsewhere.

Puzackly.

 

[MopaR&D]

A 5-speed will be a huge performance improvement over your 3-speed but "not finding anyone enthusiastic" about inspecting and repairing it? It's a manual transmission, they're basically all the same and the less speeds the simpler. Definitely a red flag to me.

 

[Dave999]

if its a street car a mustang T5 with a chevy s10 tail shaft housing
your original bell housing and clutch with a mustang plate
on an a steel adapter of no more than 6 mm between box and bell
would put the s10 shifter 1/4 in front of the chassis member that gets in the way of all other tremec installs
meaning a floor hole the size of the shifter gate housing that includes the very edge pressing of the winged W section of hump rail cut off, to allow it through. Minimum to no impact in chassis rail strength if you weld the loose ege back to the tunnel.
the drivers side edge of the top of the box will rub the tunnel so you need to air hammer that bit up a bit.
you will need a chevy speedo drive mounted on the output shaft with a split collar and a chevy t5 speedo bullet and gear
and you will need to weld up a platform on the bolt in rear mount cross member for an after market chevy or ford t 5 trans mount

Mustang V8 T5 or mustang V6 T5 was designed to pull around 80s or 90s mustang
approx curb weight 3500 LB with 250-302 ftlb torque

1971 318 duster 3100 Lb weight and sae NET (net with filter water pump fan and alternator connected up) 260 Ftlb Mopar used to quote gross figure. engine on dyno with nothing but ignition and fuel, cooling alternator/electric and fan all provided by dyno not motor.


not the last word in strength but with an organic clutch and street tyres
the odd squirt down the track would be fine and it would last a reasonable time

if you plan to put on slicks etc and the 318 is not standard a bigger trans is obviously going to be necessary. driving style counts

I.e Mr Ford thought that the trans was OK for a heavier/ street driven passenger car producing more torque than a standard 318
he was happy that the car would at least reach the end of the warranty period and he would not have to pick up the cost of a replacement transmission

and the later the T5, the better the materials/alloys and machining, and the longer it should last.
but the more speedo and tail housing challenges you need to over come

Mr Fords customers disagreed eventually, and he went with a 3550 style "phat" t5 and eventually swapped again to a forerunner of the TKO
a suitably modified 3550 (machine off the front shifter position box to the height of the rail) fits like the T5 above, but with the shifter box just behind the cross member but needs the front of the tunnel raised
for the grief you gain only a little on torque handling

As we know you can destroy a much stronger transmision with a slant 6 if you really try hard enough....

My car when standard came with 302 ftlb potential and a trans rated at 220
dunno what that says about torque ratings of transmissions. torque doesn't kill them, thoughtlessly applied torque.... namely shock loading kills em. hence standard clutch and tyres make sense

a lot of work and as stated above Mopars solution was the ally case a833 (out of a "feather" Duster ) 3 speed with overdrive, that fits with a standard 4 on the floor tunnel pressing. the last one of those i saw was in my own garage and it cost me £75, so its rarity value even in the UK made no difference it was cheap but involved too much floor chopping in my RHD car....

Dave

 

[340sFastback]

Brewers has 4 speeds where 4'th gear is an overdrive. So its like a 3 speed with 4'th being over drive. Not cheap but direct bolt in no floor mods. A Tremec TKX 5 spd would have better gear ratios but have to cut and modify trans tunnel and torsion bar cross member.

 

[Ken71Twister]

Thanks to everyone for your inputs and suggestions. I’ve made the decision to stay with the 3-speed setup that has served me well for almost 54 years and 200K miles. I’m having everything restored to the way I bought the car - so the cost and complexity of the 5 speed transmission no longer sounds like the something I want to do.

 

[RustyRatRod]

Thanks to everyone for your inputs and suggestions. I’ve made the decision to stay with the 3-speed setup that has served me well for almost 54 years and 200K miles. I’m having everything restored to the way I bought the car - so the cost and complexity of the 5 speed transmission no longer sounds like the something I want to do.

That's not an unwise decision. The A230 is a heavy duty 3 speed transmission and almost rivals the A833 for strength. It's a really good unit.

 

[AJ/FormS]

With your 3.91s, if you like the 3-speed ratios, then you would really love the A833od which will turn your final drive to 2.85; with 27" tires currently cruising at 55@2780,
this would go to 78@2780 in od; (or 65=2310)
This is a fantastic upgrade.
IMO, with the price of gas staged to skyrocket, you really ought to consider the A833-overdrive, and in your case, this is a fairly economical swap.
----------------------------------------
I ran my lo-compression 318 with 4.30s for a while, at 71=2780, and loved it. The starter gear of 3.09 x 4.30=13.29 was killer fun.
IMO tho, a starter gear of 11/1 is plenty, so I went down to 3.55s and 65=2100 . This was a fun combo.
However, the stock-cammed high-compression 318 will pull 65 down to 1800 very nicely, and with a manual trans, even down to 1600. I have cruized my lo-C318, down even lower than that. The problem with that was, no passing power.
At 65=2100in od, direct is ~2880; which still has modest passing power.
I liked 65=2200, where direct is 3020@65/ or 55=2560, again, good passing power, and IMO a reasonable compromise. This is with 3.73s.
Yes, at one time I had a parade of assembled chunks to slide in the back, nearly complete from 2.76s to 4.30s missing only, 3.73.s ; and I had some racegears too, 4.88 and 5.13s. and SureGrips in every one.

 

[matthon]

Passon Performance A855, is the only one that offers a direct bolt in

No longer available.

 

[RustyRatRod]

No longer available.

Thank God!

 

[340sFastback]

Could go with a 323 rear gear or so if staying with 3 spd.

 

[Dave999]

looking at internet pics of A230 looks like you would have a tunnel and floor that could accommodate A833 4 speed or A833 overdrive i.e both side shifted boxes with shift rods that run up the side of the tunnel...i.e won;t fit an auto floor pan but would fit a manual floor tunnel....

you'd need an appropriate bell (more so for the OD box, has a huge bearing retainer flange) and shifter but the rest i assume would fit

i.e you have options even after all the work is done

Dave

 

[matthon]

Can have the OD bearing retainer turned down to fit your bellhousing.