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T-Series TF 5 speed conversion AND upgrade 4.55 Rear -- any driving problems?

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55MGTF

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I am thinking of converting my stock TF 1500 to the T9 5 speed transmission and changing the rear to a 4.55. I have heard that doing this is not a wise idea. That it is better to do one or the other but not both. Apparently the new gear ratios in both the trans and the rear leave the car unable to get out its own way (there is not enough torque in the engine). Has anyone done both conversions? if so do you find the car's acceleration better or worse than stock? If anyone is wondering why I want to do this --- it is because I want to have both good acceleration and lower RPM's in the higher speeds (around 45 to 60 MPH). Now if there is a better solution to my objective I'd like to hear that too. I am open to all opinions. Thanks
 
A friend of mine has a TF1500 with a taller rear end (might be the MGA 3.90 rear). I've never driven it, but he's commented that it's better for touring but can struggle a bit on the uphill (we're in the mountains).

Best I can suggest is to figure out your target RPM at your cruising speed and see what gets you there. The 5-speed alone might just do the trick.
 
If you have a 4.8 rear, STD in the TF and are going to a 5 speed transmission, might I suggest you leave the 4.8 in it. Many rears have been changed with taller ones along with the 5 spd. transmissions and the guys were sorry afterwards. I would try the transmission change first and do the rear later if you deem it necessary. PJ
 
The standard swap for the rear end gears is the 1500-1600 MGA with the 4.3:1. The MK II had a 4.1 gear. You don't want to lug or drive a T series engine at speed under its power range. The Stock TF 1500 gear 4.8 is a great choice.
 
"If anyone is wondering why I want to do this --- it is because I want to have both good acceleration and lower RPM's in the higher speeds (around 45 to 60 MPH)."

You can have one or the other, but not both with the XPAG/XPEG engines. The best you can do is to find a compromise that will let you have a little of both, but you have to chose carefully. What you do not want to do with the XPAG/XPEG engine is to lug it down continuously, which will ultimately result in a broken crankshaft-$$$$$. Cheers - Dave
 
the FORD T9 Gearbox https://picasaweb.google.com/112770819864514987162/MGTDWorksAndProjects#6106847293806531410
normally used on the KIT have little difference on the gear 1-2-3-4- from the T gearbox ---so the advantage are ONLY the 5 gear
https://picasaweb.google.com/112770819864514987162/MGTDWorksAndProjects#6106486470653045794
if you would maintain the good acceleration the KIT is the way - https://picasaweb.google.com/112770819864514987162/MGTDWorksAndProjects#6106484414483163762
NOT changing at the rear axle- saving work and money
you will have lower RPM on highway (5 gear)
 
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