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4cl t5 swap questions

sc0terdad

sc0terdad

Active member
Joined
May 1, 2020
Location
Victoria, Bc
so I have recently bought a 4cl t5 transmission, (I am sure that a thread like this may be better suited to a mustang forum but I figured that due to the fact that the transmission will be going into a volvo, this would be the place to ask.)

what I was wondering: I have read that the 4cl t5 transmissions have a shorter 1st gear than the other t5s and that it makes the 1st gear very "spinny"

does anyone have experience with a 4cl t5 swap and how the driving experience turned out?
do you have any suggestions?

thanks.
 
I've had both. 4cyl behind a b21ft with a holset he351. 83 244, 3.73 auto rear end. Horrible ratio combination, geared like a truck, 1st was good for 3 car lengths. Hated it. 3.31 or lower may have made it tolerable but still not ideal.
Second was a WC V8t5 behind a b230ft in a 90' 70, first with 3.31 manual rear end, that was too tall for my liking, 2nd was miles deep, 3rd was a big jump. 1800 rpm on the hiway at 100km/hr. Swapped in a 16v 4.10 rear end, perfect combo. lots of legs in first to build some boost, nice gaps between second and 3rd, 5th is 2350 rpm on the hiway at 100km/hr.
If you are doing the t5 swap, hold out for the proper ratios, it can make or break the car.
 
Tentshedtrev said:
I've had both. 4cyl behind a b21ft with a holset he351. 83 244, 3.73 auto rear end. Horrible ratio combination, geared like a truck, 1st was good for 3 car lengths. Hated it. 3.31 or lower may have made it tolerable but still not ideal.
Second was a WC V8t5 behind a b230ft in a 90' 70, first with 3.31 manual rear end, that was too tall for my liking, 2nd was miles deep, 3rd was a big jump. 1800 rpm on the hiway at 100km/hr. Swapped in a 16v 4.10 rear end, perfect combo. lots of legs in first to build some boost, nice gaps between second and 3rd, 5th is 2350 rpm on the hiway at 100km/hr.
If you are doing the t5 swap, hold out for the proper ratios, it can make or break the car.
Click to expand...

frankly I don't know much about gear ratios, I get that the 4cl t5 is probably not ideal, but would it be combatable with a diffrent rear ratio, I own the 4cl t5 as of now and would rather not have to sell and rebuy.

would you consider it worth it to sell the 4cl or attempt to gear it differently with a rear ratio?
 
I've been doing some research into ratios and while the 1st on the V8 T5 gearboxes does seem better overall than the stump puller the 4 cylinder T5 or M45/46/47 family got, the overdrive seems a bit too aggressive for what is ultimately a four cylinder car. But luckily it seems relatively easy to swap the 0.68:1 OD gears for something in the 0.7-0.8 range.
 
sc0terdad said:
frankly I don't know much about gear ratios, I get that the 4cl t5 is probably not ideal, but would it be combatable with a diffrent rear ratio, I own the 4cl t5 as of now and would rather not have to sell and rebuy.

would you consider it worth it to sell the 4cl or attempt to gear it differently with a rear ratio?
Click to expand...

That was why I pointed you to the gear calculator. Find your box tag and check the ratios against the calculator. It?ll give you a good idea in mph of what each gear will do for a given rpm and tire/rear end ratio.

Everyone has a different driving style, so you may find that something is or isn?t for you.
 
cwdodson88 said:
That was why I pointed you to the gear calculator. Find your box tag and check the ratios against the calculator. It?ll give you a good idea in mph of what each gear will do for a given rpm and tire/rear end ratio.

Everyone has a different driving style, so you may find that something is or isn?t for you.
Click to expand...

thanks, I will do that for sure.

I kinda skimmed over the part where you mentioned the gear calculator.
 
There are many combinations of the BW-T5 transmission. The best for our cars seems to be the one that was on Cobra Mustangs with the 2.95 First gear ratio. The WCT5z. It has the most friendly spread of ratios in it IF you plan on regearing the rear diff to a 3.73, 3.91, or 4.10 gear.

Even with a 4.10 gear you end up spinning about the same RPM in 5th gear as the stock M46/47 with a 3.31 geared car does. But it will actually move when you hit the throttle and the gear spread is much more friendly for spirited driving.
 
sc0terdad said:
thanks, I will do that for sure.

I kinda skimmed over the part where you mentioned the gear calculator.
Click to expand...

Forgot to add the link.
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

My .02? using a 3.35 t5 gearbox with a 3.73 was dumb on a 245/45/17 (25.7? tall tire). First gear at 6k was ~35 mph, second at 6k was ~60, 3rd 90, 4th 120, 5th would be 180, but I never got there. And the low reduction rear made for bad days in the parking lots, starting on hills, and ultimately killed a couple clutches. Literally couldn?t get moving without barking the tires or roaching my clutch.

MY preferred driving style would have more fun taking that rear ratio to a 4.11-4.56. Yeah, first gets really short and top speed is lower, but I would have had a better time keeping clutches alive with hills and such, and been able to get into second gear at the local auto-x days when the Miata guys set up the track.

Going to a 2.95 box may have been nice, but I like my stump puller 1st for parking lots and partying. YMMV.
 
cwdodson88 said:
Forgot to add the link.
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

My .02? using a 3.35 t5 gearbox with a 3.73 was dumb on a 245/45/17 (25.7? tall tire). First gear at 6k was ~35 mph, second at 6k was ~60, 3rd 90, 4th 120, 5th would be 180, but I never got there. And the low reduction rear made for bad days in the parking lots, starting on hills, and ultimately killed a couple clutches. Literally couldn?t get moving without barking the tires or roaching my clutch.

MY preferred driving style would have more fun taking that rear ratio to a 4.11-4.56. Yeah, first gets really short and top speed is lower, but I would have had a better time keeping clutches alive with hills and such, and been able to get into second gear at the local auto-x days when the Miata guys set up the track.

Going to a 2.95 box may have been nice, but I like my stump puller 1st for parking lots and partying. YMMV.
Click to expand...

Amazons and 140s usually got 4.10 to 4.56 rear ends to pair with the M40/41's 3.13:1 1st gear. I can't imagine going lower and expecting any sort of life from my clutch.
 
The simple answer is that we have better clutches now. They can stand a lot more heat and the pressure plates clamp harder than they did in the 70's.
 
HiSPL said:
The simple answer is that we have better clutches now. They can stand a lot more heat and the pressure plates clamp harder than they did in the 70's.
Click to expand...

Brand spanking new fx400 from yoshifab, slightly lightened 22lb flywheel. With that combo, no likey feathers, so on/off or ruined. Personally 3.35 first on a 3.73 rear is silly long without diesel torques to get you rolling, higher rear reduction puts more torques to the tire, so I?d rather run a 4.11-4.56. Big heavy 28# flywheel might have helped, but doesn?t fit my driving style. Personal preference. I have friends that love having super close gears and starting in what feels to me like a good second gear, but personally, I don?t. Also I don?t really see the need for crazy top speed, so my preference is wide step 1-2 and closer 2-5.
 
I run 225/60R15 tires (25.6" diameter) and have the 4.10 rear end. The 4.03 first gear on the m47 is laughably short and I grind the synchro shifting into second if I rev too high and shift too quickly. The t5 with a 2.95 first on my 4.10 rear (12.1) seems like it would be a lot of fun with very close gears, but that would be even slightly taller than cwdodson88's 3.35 first on 3.73 rear (12.5). Is it really that bad?
 
I want this ratio because I don't do any drag racing. I want the close 2-3-4 shifts and a steep rear gear. I'm building a canyon carver. The fact that the WCT5z also has a .63 5th gear is incredibly appealing since you can run that steep rear gear, but still cruise in 5th on the highway at normal RPM....
 
so I was considering maybe, since I already have the t5 with the 3.97 1st that to combat that ratio it would pay off to use a 3.31 rear end making 1st gear idle at somthing 10 kph and be good till somthing like 24kph ish

or does this seem a bit aggressive for what is ultimately a redblock car?

and should have 5th cruising 3500rpm at about 107kph with extra legs for high-ISH (not really) top speed
 
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sc0terdad said:
so I was considering maybe, since I already have the t5 with the 3.97 1st that to combat that ratio it would pay off to use a 3.31 rear end making 1st gear idle at somthing 10 kph and be good till somthing like 24kph ish

or does this seem a bit aggressive for what is ultimately a redblock car?

and should have 5th cruising 3500rpm at about 107kph with extra legs for high-ISH (not really) top speed
Click to expand...

It's doable, but it'll end up being kinda lazy around 40-80 mph. You'll never get any "top speed" out of a 240. They hit a serious wall around 100 and it takes cubic dollars to get past that.
 
HiSPL said:
It's doable, but it'll end up being kinda lazy around 40-80 mph. You'll never get any "top speed" out of a 240. They hit a serious wall around 100 and it takes cubic dollars to get past that.
Click to expand...

intentions for the car is somewhere between 250-300 whp, it should be achievable to exceed 100kph with numbers like that right, i've driven Toyotas with 170hp that've gone 160
 
Ah. I was measuring in freedom units. I meant at 100mph/160kph the 240 hits a big aerodynamic wall. With 300 Hp you'll be able to go faster, but not that much faster with a big lazy gear in the rear end. It'll be faster in 4th gear than it will be in 5th.
 
HiSPL said:
Ah. I was measuring in freedom units. I meant at 100mph/160kph the 240 hits a big aerodynamic wall. With 300 Hp you'll be able to go faster, but not that much faster with a big lazy gear in the rear end. It'll be faster in 4th gear than it will be in 5th.
Click to expand...

I mean do you really need a 240 to do more than 100MPH?
 
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