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5 MT Full Time versus 5 MT in an '87 RX


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11 replies to this topic

#1 pghiocel

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Posted 20 August 2013 - 09:11 PM

Forgive me for starting a new thread, I've been trying to research this thru the search function but haven't gotten much success on a definitive answer.

 

I plan to campaign an '87 RX in LeMons. It has a working 5-Speed Full Time D/R transmission. Though I can't get the "Center Diff Lock" light to turn on, so I have to investigate that.

In my LeMons experience, it is good to have 2 of everything so I am looking for a 2nd transmission as a spare and I found a rather cheap 5MT from a Subaru XT Turbo. 

 

From what I understand, it has a slightly different gearing.

5MT:

  • Gear Ratios: 1st 3.545 2nd 1.947 3rd 1.366 4th .972 5th .780, Rev 3.416 Low Range 1.59

5MT Full Time

  • Gear Ratios: 1st 3.545 2nd 2.111 3rd 1.448 4th 1.088 5th .871, Rev 3.416 Low Range 1.196

 

Is that the only difference? Is it a straight swap?

Given the application (road "racing" hehe), any recommendations on using any other Subaru transmission? Should I run a Transmission Cooler?

The eventual plan is to use the EA82T for a while but eventually swap in an EJ motor.

 

 

Thanks in advance for any advice!



#2 WoodsWagon

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Posted 20 August 2013 - 09:54 PM

Your going to be unhappy with either of those transmissions when road racing. The ft4wd has an open center diff so whichever wheel has the least traction will spin and no power will get redirected to the other wheels. The diff lock just makes it 4x4, which will not be happy on pavement and will wear on the tires. Not good during endurance racing.

 

The other transmission is FWD or 4wd, so basically the same choices. The 1.59 low range probably won't be a usefull gear split on a road course.

 

So the main consideration is whether you are content racing a pretty much FWD car or if the AWD is a requirement. Because if it is, you would do best to put the AWD guts and rear transfer assembly from an EJ transmission into an EA transmission case. But that's a bunch of work, and if you plan a complete EJ engine/trans swap down the road, not worth it imho.

 

Run it as is, bring the xt spare as it is a direct swap just you will be running it in FWD most likely. The trans doesn't need a cooler, it will be fine. Keep a spare clutch on hand.

 

Put all your effort into replacing all the coolant hoses on the engine including the small ones to the turbo and making sure the cooling system is in tip top shape. That is what is going to be the cars main weakness. An intercooler would be a good upgrade with a ridiculous hoodscoop in proper lemons fashion. Better yet,  stick the intercooler out of the hood for maximum airflow.

 

If you intend to up the boost, run a water/meth injection system if lemons rules allow. Winter grade -20 windshield washer fluid works great. Otherwise, plan on the engine blowing up.

 

The front brakes will be your other weakness. Buy the best pads you can get.



#3 86 Wonder Wedge

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Posted 21 August 2013 - 04:05 PM

I'd save the FT4WD box and sell it so you have more funds to play with and run the XT box.

 

OR you can give me the FT4WD box and rear subframe assy and I'll give you my FWD box and FWD rear subframe!  :D

 

 

and +1 to the above.

 

Cooling, cooling, cooling. Wire the A/C fan to a toggle if you have to.

 

I'd also carry a spare clutch cable just in case.



#4 Uberoo

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Posted 21 August 2013 - 05:09 PM

how close are you to the budget? $2013 or $2014? if you have the cash to spare a EJ22 and its AWD transmission would work far better,A donor car could be found cheaply, especally if it has high miles or was wrecked in some way that didn't break the engine or transmission.You would also beable to scrap/part out the donor to recoupe some of the cost.The EA82T is an unreliable POS daily driving,racing is a sure fire way to kill it quick.The FT5 speed is bad because as said above if ONE wheel looses traction then all the power is sent to that wheel.Hell for reliability sake I would swap in an EA81 if a EJ22 would be beyond budget.I for one would not stake my chances of competing/winning on a POS EA82T



#5 pghiocel

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Posted 21 August 2013 - 05:57 PM

Thanks for all the advice. I'll definitely detail how our work and races go with the RX. We are all subaru drivers ('05 STi, '06 STi, '00 RS, '12 BRZ) and we have raced 6 times with a 300zx but wanted to switch to a Subaru since they are not represented much in LeMons.

 

The way LeMons works is that after every race, you tell the judges how you did, what broke, etc. They give you a budget to fix whatever you want to fix or replace. So our plan was to campaign with the RX as stock for a while and build up a budget to swap to an EJ Engine and eventually Transmission. Right now we are a bit over budget but considering that there has not been an RX in a race yet and only a couple other Brats/Imprezas in Lemons History, I am sure they will overlook our budget. Plus, the RX suspension is super soft so I am not sure we are contender for much even in Class C. I think they worry more about the E30s and Miatas when it comes to the $500 budget.



#6 MilesFox

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Posted 21 August 2013 - 06:11 PM

With the full time and a locked diff, or the part timme 4wd  in 4wd, tou can configure the rig to run a s a FWD or a RWD by removing an axle or driveshaft. But it may not hold out under the abuse. But the same car can be fwd, 4wd, awd potentially.



#7 WoodsWagon

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Posted 21 August 2013 - 07:53 PM

How far into prepping the car are you? I ask because it might be better long term to sell the RX to a good home and campaign an  EJ car to start with. Haggard 1.8l impreza's are pretty cheap and easy to come by.



#8 MilesFox

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Posted 21 August 2013 - 08:07 PM

Do you have a thread on grassrootsmotorsports?



#9 pghiocel

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Posted 21 August 2013 - 08:42 PM

We haven't started work on the car yet as I have my wedding to deal with first. We are hoping to get it ready for the December race @ Sonoma raceway.

 

I am not sure if I would consider it in mint condition. While the body is in good shape minus a few rust spots, the interior is pretty much ruined and somebody swapped in an MPFI EA82 and it is leaking oil pretty badly from the front (I am guessing the usual oil pump seal as it looks to be coming off the oil filter).

I bought an EA82T out of a 1990 Loyale (it fit in the back seat of my STi) that I hope to put in it and get it smog legal. But I understand the sentiment about the the stock parts on it and will definitely post any parts to here that we end up taking off the car.

 

In addition to doing the motor swap, I have a stock WRX intercooler and parts from our oil cooler for the 300zx and I was looking to get a good radiator. I do agree that keeping it cool is our primary concern.



#10 Gloyale

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Posted 22 August 2013 - 12:44 PM

If the 5MT is a dual range it didn't come from an XT

 

Does it have 23 spline stubs or 25? 

 

If it's 25, and dual range but not Fulltime, it's from an Early RX.....same ratios and low range as the later RX Fulltime box.

 

If it's 23 spline, and dual range, it's just a regular GL box which is what you have the ratios listed for on the top line.

 

If it's 25 spline, and NOT dual range (no rod up the side to the front) then it could be an XT turbo single range box.  Turbo gear ratios like RX trans, but no low range.



#11 WoodsWagon

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Posted 22 August 2013 - 03:08 PM

We haven't started work on the car yet. But I understand the sentiment about the the stock parts on it and will definitely post any parts to here that we end up taking off the car.

 

It's not so much the sentiment about a stock RX, but that an EJ chassis has a massive aftermarket support for suspension and brakes where an EA does not. Anything for an EA chassis will either be retrofitted from an EJ subaru or cobbled up yourself. So as far as a longer term racing investment, it would make sense to start with the better platform.



#12 el_freddo

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Posted 23 August 2013 - 09:08 AM

I've now got a FT5spd L series gearbox behind an EJ22.  It's been great so far and I think the best thing I did with it was fit an OBX front torsen LSD, I can get the front inside tyre spinning when accelerating around tight corners in the wet, but the LSD locks up and it's not a wheel spin that gets faster if I keep pushing.

I've not used the centre diff yet and my dual range isn't hooked up to the cab.  It's on the to do list.

I'd be looking at doing what's been suggested with the single range EJ AWD box put into single range EA casings to bolt up to the engine.  But there's still modifications required to fit the gearbox crossmember, gear shift lever and prop shaft...

Cheers

Bennie






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