4 spd vs 5 spd pros and cons

Chadtidlund · #1 (**permalink**) 05-01-2016, 12:21 AM

To all Cobra replica owners reading new posts,

I'm looking to buy a fully assembled roller from Unique Motorsports in the near future and would like some feedback on what manual transmission to get; a 4 spd or 5 spd. The car will have a big block 428 pushing about 550 horsepower and will mostly be driven daily (during summer) short distance on the street; I will probably only drive on fwy or hwy occasionally. I want the car to be fast to 60 mph and in the 1/4; I'll probably take the car to the drag track (1/4 mile only) a few times to see how well it and I can do. Could also use some advice on what rearend ratio would be optimal for my intended uses; I was thinking somewhere between 3:31 to 3:73 but am wide open to suggestions.

Sincerely,
Chad

Ron61 · #2 (**permalink**) 05-01-2016, 03:53 AM

If you want the more original look then the 4 speed is the way to go. But if you plan to just drive it and enjoy it, I would go with the 5 speed and a .8 split between 4th and 5th which will kink your effective gear ratio up and help with the cruising. As for read end gears, unless you plan to drag race it seriously I wouldn't go below 3:90s and I have 3:56 in my Coupe with the .8 split and they work very well on the road race track and also on the road. My 69 has 3:91s which was the highest I could order in it and they are a little lower than I like for driving around. But my other choices were 4:10, 4:56 and into the 5:50 range.

Ron

BAsque1 · #3 (**permalink**) 05-01-2016, 06:04 AM

Quote:

Originally Posted by Chadtidlund

To all Cobra replica owners reading new posts,

I'm looking to buy a fully assembled roller from Unique Motorsports in the near future and would like some feedback on what manual transmission to get; a 4 spd or 5 spd. The car will have a big block 428 pushing about 550 horsepower and will mostly be driven daily (during summer) short distance on the street; I will probably only drive on fwy or hwy occasionally. I want the car to be fast to 60 mph and in the 1/4; I'll probably take the car to the drag track (1/4 mile only) a few times to see how well it and I can do. Could also use some advice on what rearend ratio would be optimal for my intended uses; I was thinking somewhere between 3:31 to 3:73 but am wide open to suggestions.

Sincerely,
Chad

Hi Chad:
My car has 427 Side Oiler dynoed at 550 or so and I have a 5 Speed Doug Nash, I know they are mostly used for drag racing but I am happy with the fact that at 60 mph I am at about 2300 rpms in 5th gear. I have a 3:31 rear end. My only grip is that it is a hard shifting tranny and a very close H patern.
Hope this helps
Lou

1795 · #4 (**permalink**) 05-01-2016, 06:40 AM

If you are primarily going to be driving the car around town, you might want to be in the 3.54 range. Otherwise, you will have a hard time getting the car out of second gear. Go to the second strike gear calculator and run some transmission and rear end combinations through it and se how the rpms are at a given speed. Remember, most of the engines that we use do not like chugging along at 1500 rpms. They pretty much need to be in the 2,000 and above range.

fastd · #5 (**permalink**) 05-01-2016, 07:20 AM

I can't really think of a good reason to get a 4 speed.

A 5 speed tremec with a 2.87 1st gear with a 3.31 or 3.54 rear gear is a nice combo. I would opt for the 3.31 as I like to be able to get to 30-40 mph in first gear on hard acceleration. 5th gear on a tremec can be either .82 or .67 - this gear is a matter of preference. I prefer .82 cause it makes it a usable gear. .67 is pretty much just a highway cruising gear - can't really accelerate in it. If you want to be able to drive your car at above 75 for long periods than .67 5 gear would be better.

Shootnride · #6 (**permalink**) 05-01-2016, 07:27 AM

Chad,

My car has a 427 side oiler making about 500/500 HP/Tq with a Tremec 5 speed, .64 5th gear ratio and 3.73 rear end ratio. This combination works very well and I really like the ability to cruise at 70mph turning about 2300 RPM vs about 3300 RPM if I had a 4 speed. The only complaint I have is that with the 3.73 rear end ratio and the torque available, first gear is almost not needed. I think the ideal combination would be a Tremec 5 speed with .82 5th gear and a 3.31 rear end gear. One thing for sure, I would never go back to a 4 speed transmission. I see absolutely no advantage since the 4th gear ratio in both the 4 speed and the 5 speed is typically 1:1. The only reason I can see for the 4 speed is if you are trying to replicate an original Cobra as closely as possible.

Just my two cents.

Ted

fastd · #7 (**permalink**) 05-01-2016, 07:39 AM

To add to shootride's comment, I think that he would agree that the 1st gear should be 2.87 (not 3.27).

And since these are all not original Cobras, you definitely aren't loosing anything by choosing a 5 speed. Also, resale value with a 5 psd over a 4 speed is at least a $1k in my mind.

lippy · #8 (**permalink**) 05-01-2016, 09:01 AM

I have a side oiler too (640/589 before I changed the cam, now I'm guessing 610/610 with the new cam). 4 speed looks more correct. 5 speed probably a better trans and driving experience. My TKO600 is 0.83 OD and my rear is 3.54 but I don't drag it. 5 speed is good but I almost wish I had a 6. 4 isn't enough IMO.

1985 CCX · #9 (**permalink**) 05-01-2016, 10:37 AM

4spd is period and gives you the sound and feel of the day.
5spd is better on road. Highway.

I went 4spd on last two cars.

Bernica · #10 (**permalink**) 05-01-2016, 12:17 PM

4 speed wide ratio top loader and 3:31 in the rear. Works for me!

Tim7139 · #11 (**permalink**) 05-01-2016, 03:58 PM

How about the fact that , while most don't put huge miles on these cars, a five simply requires less work, lower revs, on that expensive engine you want to keep around for a while.

Maricopa · #12 (**permalink**) 05-02-2016, 02:48 PM

Took a day trip with some other guys once, about 100 miles each way up into the mountains. On the way we ran mostly in the mid '80s, almost all of us having FFRs with small blocks and 5-speeds. One of the guys had a beautiful and very 'correct' ERA with a big block and Top Loader. We stopped for gas on the way back and he asked us to slow down, he was cranking 3,500 rpm at those speeds and getting 9mpg.

RodKnock · #13 (**permalink**) 05-02-2016, 03:05 PM

Quote:

Originally Posted by 1985 CCX

4spd is period and gives you the sound and feel of the day.

Yes, 4,000 RPM on the freeway does give you the "sound and feel of the day."

There is no reason to install a 4-speed in a replica. None. 99.99% of us own replicas, so originality is superfluous. As for looks, my TKO looks as "original" as any Toploader, unless someone has it on a lift.

It's a kit car, why worry about nonsense like this? Don't forget two roll bars for safety too.

Bernica · #14 (**permalink**) 05-02-2016, 03:07 PM

Quote:

Originally Posted by Maricopa

We stopped for gas on the way back and he asked us to slow down, he was cranking 3,500 rpm at those speeds and getting 9mpg.

Do you know what rear end he was running? Sounds like he had a low gear...

Maricopa · #15 (**permalink**) 05-02-2016, 04:32 PM

I'm guessing 3:55s. That's what's in mine and if I was running 80+ in 4th I'd be turning well over 3K.

Of course I might have fudged on the speeds a bit.....

Dimis · #16 (**permalink**) 05-02-2016, 04:49 PM

Depends how close to the real thing you want to replicate.

I wanted to replicate "it" (the experience included) with some resemblence of accuracy.
However for me, I drew the line at what "I" can't tell from 10ft away.
So when it came to gear-box, Rodknock's logic kicked in. There was NO reason for me to go 4spd. In fact if there was a 6spd I'd have gone for that.
This is one place, comparing 4 & 5spd where you can have your cake and eat it too.

RodKnock · #17 (**permalink**) 05-02-2016, 05:21 PM

And several threads down the page from this one, there's a thread titled "Toploader pops out of 3rd and 4th."

As Dimis states, "some (re)semblance of accuracy" is desirable, say like no "dune buggy Cobras" please, but there's a point of no return on someone's sanity, in terms of originality and authenticity of a replica.

No disrespect to all those Cobra replica owners with Toploaders out there, but I think your nuts! Present company excepted of course, Bernica.

Bernica · #18 (**permalink**) 05-02-2016, 06:39 PM

Quote:

Originally Posted by RodKnock

No disrespect to all those Cobra replica owners with Toploaders out there, but I think your nuts! Present company excepted of course, Bernica.

Just don't play the "Real" card. I am far from that. I just like the original feeling of what they had in the day and what I grew up with,.

DanEC · #19 (**permalink**) 05-02-2016, 06:45 PM

Transmission choice may depend on your age and past car ownership. I'm old enough that a Muncie or Toploader 4 speed just feels natural and I like the feel of a good Hurst shifter/linkage. If you are younger than me and driven mostly 5 and 6 speed cars then it's logical that's the way you would want to go.

I have a 6 speed Mustang GT for a daily driver and in town I feel like I'm driving a truck in going through all 6 gears. So, what do I do - skip a couple gears and end up driving it like a 4 speed.

It's kind of a decision you need to make based on your own experiences and preferences.

Bernica · #20 (**permalink**) 05-02-2016, 07:15 PM

Quote:

Originally Posted by DanEC

Transmission choice may depend on your age and past car ownership. I'm old enough that a Muncie or Toploader 4 speed just feels natural and I like the feel of a good Hurst shifter/linkage. If you are younger than me and driven mostly 5 and 6 speed cars then it's logical that's the way you would want to go.

I have a 6 speed Mustang GT for a daily driver and in town I feel like I'm driving a truck in going through all 6 gears. So, what do I do - skip a couple gears and end up driving it like a 4 speed.

It's kind of a decision you need to make based on your own experiences and preferences.

Couldn't have said it better! Well done Dan! I just like 1-2-3-4 and I'm all in, just like when I was a kid!