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Benefits to swapping 4 speed manual transmission to 5 speed?

4 speed 5 speed 1988 subaru gl ea 81 dual range transmission transmission swap

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18 replies to this topic

#1 88SubaruGL

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Posted 26 April 2014 - 08:24 PM

Just bought a 2nd Generation 1988 Subaru GL 3 door hatchback 4 speed manual transmission with dual range (4 hi, 4 lo) with an EA81 engine. I've been searching this forum, but haven't found alot of info regarding the benefits of swapping my 4 speed manual for a 5 speed? There are alot of posts about swapping an automatic for a 5 speed, but that doesn't help me.

 

The main reason I'm interested in doing this is I do alot of freeway driving, and I go about 65-70, which puts my rpms in the 3000-3200 range. I know that's not great for the engine, and I want this engine to last. I read on one post where a person said by swapping to a 5 speed, it lowered the rpms by 500 while highway driving. Is that true? I wanted more confirmation than 1 person before considering this. Are the gear ratios the same, or will I be able to be at a lower rpm going 65-70 if I swap to a 5 speed?

 

What does a swap involve if I'm going from the 4 to 5 speed? I read that they made them in 5 speed with the EA 81 engine those same years, mine just happened to have a 4 speed manual. Can anyone confirm it that's true, Wikipedia isn't always correct. I would think it would be easier to find a 5 speed transmission from an EA 81 than EA 82 if that's the case.....

 

Thanks for your help and replies!


Edited by 88SubaruGL, 26 April 2014 - 09:35 PM.


#2 apintonut

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Posted 26 April 2014 - 11:18 PM

Ej22 and 5speed

#3 Idasho

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Posted 26 April 2014 - 11:47 PM

The final drive ratio between the 4-speed and 5-speed is VERY close to being the same.  I seem to recall that the 4-speeds 4th gear is actually TALLER than that of the 5-speeds 5th gear, making your highway RPMS HIGHER, not lower when swapping to a 5-speed.

 

 

The biggest benefits have to do with having a better selection of gears during day to day driving, a much lower low range if it happens to be a dual range 4x4 trans, and the simple fact that the 5-speed is simply built better than the 4-speed.



#4 Idasho

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Posted 26 April 2014 - 11:48 PM

here you go....

 

Gear%20ratios.JPG



#5 bratman2

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Posted 27 April 2014 - 12:02 AM

The EA81 is a very reliable engine. I don't think there is an issue with running one 3000-3200k. Experimental airplane crowd runs them higher than that with no premature failures. I would be willing to bet that city driving and short trips would cause more wear than what you are doing.

#6 tweety

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Posted 27 April 2014 - 01:43 AM

APINTONUT.   The OP didnt mention he wanted to move to an EJ of any sort. 

 

IDASHO has a good list there.  So your 4th speed is an overdrive taller than the 5 speed.  If you feel its revving too high go for a larger tire circumference.  I had the same issue with an old English Ford Zephyr.  It had a 4 speed and I upgraded to 5 speed.  Had I known the issues and trouble I would have lowered my freeway speed from 65mph to 55 mph instead.  Sometimes the simple answers are the best.


Edited by tweety, 27 April 2014 - 01:44 AM.


#7 jono

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Posted 27 April 2014 - 06:36 AM

EA81 5 spd  4WD box, really ? Only seen FWD 5 Speed, heard about rare 5 speed 4WD touring wagon box for EA81

 

Benefits of the EA82 5 speed behind an EA81 engine is nicer shifter design, lose the old floppy EA81 4 speed shifter issues.

 

I would like to include better gearbox mounts, but I have used EA81 4 speed gearbox mounts each side, retained the EA81 gearbox x member and had no problems.

 

Bragging points having a 5 speed.

 

Hmm, point out the diff ratio is 3.9:1 for all the EA81 boxes to compare with, only 1 of 3.7 diff in whole chart !

 

I thought 3.7 was the more common, or typo ??


Edited by jono, 27 April 2014 - 06:39 AM.


#8 bratsrus1

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Posted 27 April 2014 - 09:18 AM

Hi This is Jerry, I make a 5 speed kit for your car call me and I can let you know all about it. I have a 85 hatch back and drive 500 miles a week ask me if I would go back to a 4 speed hell no. 509-952-2855 Thanks Jerry

#9 SuperBrat

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Posted 27 April 2014 - 10:02 AM

Call Jerry, he is the guru of what your wanting to do, been in his hatch for a ride, its a bullet.............. :lol:



#10 bratman2

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Posted 27 April 2014 - 05:31 PM

A 5 speed isn't going to help him. Sloppy shifter, that's an easy fix. Did mine years ago and still tight as a drum.

Tweety gave the best answer to achieve what the OP wants. Dawned on me today but I have been busy so have not replied until now. I run 185/75-14 Uniroyal tires on Peugeot 14" steel wheels. Fit great, speedometer is off by 14% roughly. Had it checked by a coworker behind me, 52-53mph was 59-60 mph indicated in his late model Eclipse. So if 88SubaruGL's Subaru speedometer is the same as mine he could obtain 70 mph at roughly 61 mph indicated. All he needs to do is check all the salvage yards around him until he finds a Peugeot 504/505 sedan. Buy the wheels and get some tires. Simplest of all.

#11 88SubaruGL

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Posted 27 April 2014 - 07:15 PM

Thanks to everyone who replied, I am going to hold off on the 5 speed conversion at the moment, Jerry, I will keep your number in case I change my mind to get more info on the kit you suggested. For now and since my cash is limited, I will focus on getting bigger tires. I already planned on getting it lifted (4 inches), so I think the bigger wheel/tire option is best right now. Thanks again for all of the help/suggestions!



#12 bakerjr

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Posted 28 April 2014 - 01:09 AM

So do bigger tires lower or raise the gear ratio? Sorry for the stupid question

#13 tweety

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Posted 28 April 2014 - 01:57 AM

Larger tires increase your speed for the same revs.   You can get onto a tire calculator and compare tires, circumference, diameter, etc.  see   

 

http://tire-size-con...ze-calculator/ 

 

you'll see on the right hand side of the site different speeds for given tires.

 

One trap here apart from guard clearances is that hills will cause the car to drop back speed sooner.  Just like marriage.....lust comes at a cost...



#14 jono

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Posted 28 April 2014 - 07:46 AM

get hold of the speedo function of a GPS device to check your speed - checking it against another car may get differing results from brand to brand

 

Fitting bigger wheels and tyres, increasing your nominal overall tyre diameter will make you think you are within the speed limit, until the fuzz jumps out of the shade - radar gun pointing at you !



#15 bratman2

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Posted 28 April 2014 - 09:49 AM

Had not thought of the GPS. My daughter next door has one I can borrow for an accurate reading. With mu old set of 185/80-13 tires which were around 1/2" shorter height than the 14" tires I have now a radar trailer showed my speedometer to be 10% off. I feel pretty comfortable with my estimate because people fly on these back country roads to the mine I work at. Typically they run just over 60 with some getting close to 65. I maintain traffic speeds at 52-53mph and maybe get passed once or twice every now and then on my commute. I would not be surprised to see differences in these old Subarus with the same size tires on them! So I don't think the tire calculator would be the way to go. Years ago with 195/75-14 tires my speedometer was over 15% off checked against my wife's Mustang with new tires and later here 03 Legacy when it was fairly new, 51 mph indicated came up to 60 on both of her cars locked in cruise. Just food for thought.

#16 wagonist

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Posted 28 April 2014 - 10:54 PM

Yeah, but most new cars now under-read on their speedos. We used to have a +/- tolerance in the Aus design rules, but then 1 state started booking people for 3km/h over the limit (so not good at 110km/h), so now the tolerance is 0 to -10%, and most would err on the negative side just to be sure.

 

You can still use another car's speedo as a reference, it'll still work.



#17 bratman2

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Posted 29 April 2014 - 06:32 AM

My daughter's Garmin displays mph. It matches my wife's 2011 Forester XT exactly.

#18 bratsrus1

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Posted 29 April 2014 - 08:56 AM

Hi This is Jerry, come to my house and I will give you a ride in my hatch that will change your mind. The gears are much closer than the 4 speed got so you don't have that lag. With this kit everything is still stock inside of your car. When you change to a 5 speed your going to say why didn't do this along time ago so much better. Thanks Jerry

#19 coxy

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Posted 10 May 2014 - 08:10 AM

EA81 5 spd  4WD box, really ? Only seen FWD 5 Speed, heard about rare 5 speed 4WD touring wagon box for EA81

 

Benefits of the EA82 5 speed behind an EA81 engine is nicer shifter design, lose the old floppy EA81 4 speed shifter issues.

 

I would like to include better gearbox mounts, but I have used EA81 4 speed gearbox mounts each side, retained the EA81 gearbox x member and had no problems.

 

Bragging points having a 5 speed.

 

Hmm, point out the diff ratio is 3.9:1 for all the EA81 boxes to compare with, only 1 of 3.7 diff in whole chart !

 

I thought 3.7 was the more common, or typo ??

Jono the EA 81 did have a 4wd 5 speed but only in the rare RX MY series models with the so called EA81S twin carb engines, Possum used to love that RX coupe more than any other rally car he drove especially as it was a dual range setup but only like the RX turbo with a relatively small low range reduction unlike the wagons.

That gearbox with so many ratios to choose from and an engine that revved to the moon must have been a revelation when everything else was still RWD or FWD or a Hell Expensive Works Quattro.

The Subaru RX was well before the more common Mazda or Ford TX3 being just a rebadged  GTR or  GTX  Familia  4WD Turbo.

Therefore driving an RX Subaru in the early eighties was a big advantage over everybody else when it was wet and slippery.







Also tagged with one or more of these keywords: 4 speed, 5 speed, 1988 subaru gl, ea 81, dual range transmission, transmission swap

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