Differences between 5speed and automatic

rommaster2 · Post by **rommaster2** » Wed Sep 22, 2010 9:41 pm

Hello, i'm interested in owning a merkur in the near future and was wondering what the exact differences other then the obvious. I know that the autos have less horsepower which i assume is from less boost, do they run a different ecu?

The reason i ask is because if i can find an automatic thats a killer deal (for some reason northern california doesn't seem to have the best supply) i'm trying to figure out what all woudl have to go into changing it from an auto to a 5 speed. Labor wise i can do it all, i'm a decent enough mechanic and have done tranny swaps before on a couple cars as well as rebuilt engines and suspensions.

So i guess the main concern is what are the differences and how hard is it to get a hold of some of the parts required for a swap.[/quote]

IceColdMikey · Post by **IceColdMikey** » Wed Sep 22, 2010 10:13 pm

Hey, welcome to the forums!

Doing the swap is easy enough. I'm soon to do mine, auto to T9, once I figure out a few other issues she's having.

Suffice it to say you'll need:

Transmission, driveshaft, pilot bearing, pedal box, clutch cable, new clutch kit if it doesn't come wit the transmission.

No need to change ecu at all. Boost can be raised, and timing will need to be changed.

Pretty basic actually.

Mike.

xrattiracer · Post by **xrattiracer** » Thu Sep 23, 2010 10:30 am

regardless of which option you get, you will want to swap in a T5 so its not as important as you might think. the 5 speed pedal set can be a bit hard to find though.

MerkXRTurbo · Post by **MerkXRTurbo** » Thu Sep 23, 2010 11:17 am

Less boost (10psi max, rather than 15psi), different computer programming (IIRC auto ECU actually has more timing advance), taller gearing in the rear end (3.36 auto, 3.64 manual).

rommaster2 · Post by **rommaster2** » Thu Sep 23, 2010 2:46 pm

yeah the pedal set was the part i was worrying about finding really. T5s arent too hard to get a hold of.

So i'm guessing i'd need an adjustor to raise the boost to 15lbs, if i'm doing that i'd wanna run a different computer for sure if the timing is advanced more on auto.

as far as the differential that could be an issue i've got a friend who does rear diffs professionally but i'm not sure where i'd get rear gears for this diff.

Post by **hEaT** » Thu Sep 23, 2010 4:13 pm

rommaster2 wrote: So i'm guessing i'd need an adjustor to raise the boost to 15lbs, if i'm doing that i'd wanna run a different computer for sure if the timing is advanced more on auto.

as far as the differential that could be an issue i've got a friend who does rear diffs professionally but i'm not sure where i'd get rear gears for this diff.

MBC's can be had for cheap. This one works ok:

http://www.boostvalve.com/

As for the computer, the stock auto computer is fine. Just set base timing 13* BTDC like the manuals instead of 10*. No issues with the MINOR increases in timing throughout the curve, especially if you are intercooled.

Diff will be fine. The 3.36 is actually better if you swap to a T5 if you get one with the stump-pulling 3.97 first.

Post by **DPDISXR4Ti** » Thu Sep 23, 2010 10:28 pm

Everything Joe says is spot on.

As for the pedals, no biggie - I know I have a couple spare sets on the shelf, as do others.

Esteban · Post by **Esteban** » Fri Sep 24, 2010 1:19 am

I actually hate the auto diff with my T5. The 3.36 diff paired with a .73 5th gear doesnt rev high enough for freeway cruises. I'll be installing a manual diff next month to cure that issue.

If you're a car nut like most of us, then go for an automatic if thats all you can find. I was fortunate to find one in San Diego for $500. Its fun working on them even though you'll build a love hate relationship with it.

rommaster2 · Post by **rommaster2** » Fri Sep 24, 2010 1:20 am

good to know, now i just gotta get the car.

Its funny cause i'm used to thinking in terms of using a v8 t5 like in my falcon. I can run 3.80s and still turn reasonable highway rpms (hows 75mph at 2500rpms sound). Though i have a six cylinder that doesn't put out near as much horsepower as these 2.3s, it definetly is torquey and fuel efficient. 27mpg highway and 24 in city

. I am definetly looking forward to getting a merkur, RWD, turboed 4, quirky styling (i'm a sucker for anything different). The best thing though is it gives me something to fiddle with, ADD has made it to where i enjoy a challenge and between my falcon and in the future a merkur I think i will be very happy

ex_are_four_tea_eye · Post by **ex_are_four_tea_eye** » Sun Oct 03, 2010 2:27 am

I did not like the auto diff with the T5 either. Car felt way too sluggish.

One interesting thing to note, when I went to a 3.64 (manual) diff, my 70mph highway RPM in 5th gear remained the same. I still have not figured that one out.

Esteban · Post by **Esteban** » Sun Oct 03, 2010 3:51 am

You switched the diff and the freeway RPM didnt change? Thats almost impossible by any math standards

RatFink · Post by **RatFink** » Sun Oct 03, 2010 9:03 am

ex_are_four_tea_eye wrote:I did not like the auto diff with the T5 either. Car felt way too sluggish.

One interesting thing to note, when I went to a 3.64 (manual) diff, my 70mph highway RPM in 5th gear remained the same. I still have not figured that one out.

your spedometer is driven according to driveshaft revolutions (gear ratio). If you had a GPS you would see your speed @70 has changed between the two.

IceColdMikey · Post by **IceColdMikey** » Sun Oct 03, 2010 9:24 am

RatFink wrote: your spedometer is driven according to driveshaft revolutions (gear ratio). If you had a GPS you would see your speed @70 has changed between the two.

He said RPM, not speed.

Camaro5690 · Post by **Camaro5690** » Sun Oct 03, 2010 12:18 pm

IceColdMikey wrote:
RatFink wrote: your spedometer is driven according to driveshaft revolutions (gear ratio). If you had a GPS you would see your speed @70 has changed between the two.
He said RPM, not speed.

What Mike was saying is he isnt really going 70, his speedometer is off from the gear change. So therefore his RPMs at 70 are different.

ex_are_four_tea_eye · Post by **ex_are_four_tea_eye** » Sun Oct 03, 2010 6:12 pm

When I did my T5 swap last year, I used the correct driven gear so that the speedo would read accurately. This was confirmed with a Garmin GPS.

When I swapped out diffs this year (3.36 to 3.64), the speedo read 5mph fast at any speed (as expected since I haven't changed to the NEW correct driven gear yet). This was also confirmed with the same Garmin GPS.

My RPM now(going by stock tach) at 70mph (going by GPS) are just a hair higher, by maybe 50 rpms. It's such a slight increase that I doubt the stock tach is even that accurate. Certainly not enough increase to ruin my gas mileage.

It makes me wonder if 5th gear was changed at some point in my T5, or if I have a V8 box. But, it came from a guy who has several 4cyl. mustangs in their household, and he never noticed anything different about the gearing in this T5.

YMMV