Need Advice Before I Pull The Trigger on EJ22 Swap

I'll try to be brief.

 

I have a 98 Outback with a blown (2.5L) motor due to a broken timing belt. I bought this car used from a Subaru mechanic who claimed to have put new headgaskets, timing belt, etc. on the car. A month after I bought it, the transmission went out. I have now owned the car for six months and now this!

 

From everything I have read here, it would seem to make sense to ditch the 2.5 and swap it out for a 2.2. I have located one from a 96 Legacy (auto) that reportedly has 112K mi and runs well.

 

But before I proceed with dumping another $1,500 into this car, I need your advice on something else that the car was doing before it died.

 

For the past 3-4 weeks, I have noticed the car "shaking" (for lack of a better word) when I drive approximately 40-55 mph. I don't notice it at lower speeds and it stops once I exceed 60 (which is most of the time;)). This "shaking" or pulsating has me worried that there might be something going on with the differential. I have this nagging fear that the transmission I bought has the wrong gearing ratio and could be causing damage to the diff. It is supposed to be from a 98 with a 2.5, but I don't know how to verify this.

 

Also, I had a flat tire about 3 months ago and the puncture was near the shoulder of the tire so it could not be repaired. The tires still had 50-60% tread, so I just bought a used tire (exact same size, but different brand) and had it put on. Are the tolerances so close that this could be causing the problem?

 

So, before I pull the trigger, I need your advice.

 

Does this sound like it could be related to the rear differential?

 

If so, is the diff still salvageable or is the damage done?

 

How do I confirm the root cause of the shaking?

 

If I do pull the trigger on the swap, do I need to plan on replacing all 4 tires at the same time?

 

I hope that wasn't too much for my first thread. I appreciate your help!

the tires do need to be the same size, within 1/4 inch in CIRCUMFERENCE.

 

but an off brand tire may work for a bit if it measures the same as the others. it is a very, very long shot, almost impossible, that a random tire of the same ''size'' would actually measure the same circumference. plus different brands of tires will wear at different rates. so even if it happens to match now it may not match in 10k miles.

 

the shaking is probably tires out of balance.

it is probably not the front diff.

there are several things you can do.

first, install a fuse in the FWD fuse holder under the hood, passenger side near the firewall. (any size fuse will do.)

this will / should disconnect the rear wheels and eliminate the tire mis-match (tire or trans/diff) as a cause. then test drive the car. does it help?

rotate the tires front to rear, then test drive the car. does it help?

check the tire pressure.

 

read and report the trans ID# on the trans bell housing near the starter. it should be something like TZ102Z2DBA. read it, and write it down. do not rely on your memory, they all are very similar.

 

if the tires are balanced and rotating them does not ''change'' the shaking, better /worse / same, get under the car and start pulling and pushing on all the suspension and steering parts. something may be lose or worn.

 

if trans is right and the fuse corrects the issue, you will need 4 matching tires, same brand, size, tread pattern, wear, and inflation. but it that is a deal breaker financially you can remove the rear section of the drive shaft (front section must stay). this will disconnect the rear wheels until you can replace the tires.

 

this is also the mid to long term fix for mis-matched differentials, the wrong trans.

for a very short time you can run with the fuse in, maybe for a while, but it is not recommended as a long term solution.

 

check things out and report back.

 

i hope i have not confused you with too much info.

Adding to Johnegg's excellent advice ... using a tape measure, measure all four tires around the middle of the tread (or as close as possible without a lift) and reply with your measurements here.

The car is currently not running and is sitting in my mechanic's parking lot waiting for me to make a decision regarding it's fate.

 

Based on what you've said, it looks like I'm safe to proceed with the swap (with the caveat that the numbers on the transmission indicate that it, indeed, is from a 2.5L).

 

Once it's done, I will report back with the results of inserting the fuse, checking tire balance/air pressure, etc.

 

You guys are a wealth of information - even if a lot of what you say is WAY over my head. In fact, I've printed off a previous EJ22 swap discussion thread to give to my mechanic for his reference.

 

You guys are the best. Thanks!!

We do what we can.