One of the first things I noticed after installing the Type 9 was slower acceleration. I'm guessing this is due to both the extra weight of the box and more rotating mass on the mainshaft?
 
Anyway, it's made that much of a difference that I'm considering putting the 4 speed back in. And also changing the diff gears to 3.54, a ratio that I haven't tried yet. 
 
At the moment it's 4.125. What a wasted exercise that was.
Previous was 3.77 which I liked and suspect might be going back in after trying the 3.54. I used the 3.77 with the four speed and the car felt really quick. My camshaft is Crow Mild street so lots of torque down low. I'm hoping this will help with the gap between 1st and 2nd when the 3.54 is installed.
 
Any thoughts???
 
EOI in the type 9 and 4.125 diff gears are welcome. The box is in perfect order and 4.125 has just been serviced by a reputable diff specialist.
 
 

Extremely strange about the slower acceleration.
The minimal extra weight of the Type 9 definitely wouldn't have a noticeable affect.
Have you checked each of the gear ratios for each gear and compared with the original gearbox gear ratios?
 

Hi Peter
The type 9 is a 4cyl Sierra box so ratios are same as the four speed + overdrive.
I can notice the most subtle differences in the car when it comes to weight, such as alloy wheels compared to steel.
I think the T9 is about 10kg heavier than the 4 speed?
 

I read that the 4 speedbx is 22kg and that the type 9 weighs 11 kgs more:
 
http://www.type9gearbox.co.uk/type-9-history.html
 
 
 

I cant see 11 kg`s making that much difference, i`d check the gearing if i was you
 

You're running a 1600 aren't you I think ?  If so I'm not sure you're going to like the 3.54 too much.  I'm a real fan of the Kent motors and have them in both of my Escorts (thats a 1600 in my profile pic) with no plans to change.  But they're no torque monster.  I wouldn't go near a 3.54 without a 2 litre up front.  
 
As to the first/second gap not sure there is much you can do short of putting in a Rocket box but then you're initial take off will be slower, once moving they are great and that gap disappears, first gear becomes useful again.
 
I really would have thought the 4.1 and Sierra box would have been an awesome combination.  I didn't realise the weight difference between the 4 and 5 speed was so much.  Bear in mind that the extra 11 kg's isn't all going to be in rotating parts, some is going to be the case, etc.

130bhp pinto

You can get them with a taller first gear in the UK:
 
http://www.bghgeartech.co.uk/html/4_speed.html
 
Just don't look at the price!

Your slower acceleration doesn't make sense, in that a standard 4cylinder/petrol application T9 has exactly the same ratios as a standard type E 4 speed (3.65,1.97,1.37 & 1.00, 5th =0.82). It is true that the weight penalty is an additional 11kgs over the 4 spd 22kgs but I doubt it would be noticeable. I assume the 4spd box you are talking about is the single rail type E.  Have you determined the 1st gear ratio? You don't have a Ford 4spd rocket box (2.54 1st)? Or you don't have another T9 variant? Diesel  T9(3.91 1st) with a modified input shaft which would be terrible behind a small engine or modified Capri T9? 
When you say slower acceleration do you mean in each gear or overall through the gears? People do fit a modified version of the Capri 2.8i box (modified input shaft again) to get the taller 1st gear(3.36) but that has slightly taller 2nd & 3rd gears (1.81 & 1.26) so acceleration within 2nd or 3rd gear will be slightly slower.
SFE

Yes, all the same ratios as a 4 speed. Slower acceleration as in 0.3 second over 400m