I just recently purchased this vehicle. How fast can I go on the highway? Sounds like its going to explode at 60 mph. Is it a huge job to swap it out with a 5 speed?

The 3-speed is a decent transmission,  It has a bad rep here mostly because most of the members seem to prefer manual transmissions.  The automatic suffers if given poor maintenance.

 

That being said, there is very little engine speed difference between the 3AT and the 5-speed.  Either way, you will see near 3500RPM at 60mph.  This is normal.  Do not be concerned:  It will tun nearly forever at even higher engine speeds, provided normal maintenance.

 

Our 89 with a 3AT would easily cruise at 80mph, with power in reserve.

These little motors will run out pretty well, so it's O.K. to cruise 70 with the engine turnin 4k rpms.

 

That being said, I usually keep my 3AT under 65.

 

 

Northwet....I think you are off some...the 5 spd DEFINATELY offers lower RPMs at higher speed.  3rd gear in the 3at is 1:1 drive through the trans, then 3.9 final drive unless turbo. 

 

5spds, 4th gear is .972, and 5th gear is .78 : 1 so both are overdriven. 5th by quite a bit.  With the same 3.9 final drive the 5spd is definately taller geared overall.

Edited November 29, 201312 yr by Gloyale

I very well could be off (in oh so many ways :-) ), but not so much as I have noticed.  My turbo 5-speed turns a little slower than the 3AT version, and the non-turbo 5MT vs 3AT seemed to be a couple 100 rpm difference... not so much as I noticed much or cared.

 

Cheers!

Ah!  A thought... Is it actually upshifting into 3rd gear?  Give a couple RPM@speed values (above, say, 35mph) if you are not sure

I very well could be off (in oh so many ways :-) ), but not so much as I have noticed.  My turbo 5-speed turns a little slower than the 3AT version, and the non-turbo 5MT vs 3AT seemed to be a couple 100 rpm difference... not so much as I noticed much or cared.

 

Cheers!

 

Turbo 5spds have a lower 2nd thru 5th gears compared to N/A.....they are 3.7 final......but still end up actually running slightly higher RPMs than the NA.  But makes sense the turbo car would feel close to the 3at at 60ish.

 

I definately notice that the 3at runs higher RPMs than either 5spd though especially above 70.....the gap widens the faster you go. 

 

At 60, the 5spd will be around 3300 and the 3at will be at 3600.  Not so bad, but.......

 

At 80 the 5 spd will be around 4300 rpms, but 80 in the 3at is 5300 rpms

Ah!  A thought... Is it actually upshifting into 3rd gear?  Give a couple RPM@speed values (above, say, 35mph) if you are not sure

 

Nah.....you can't go over 45~50 in 2nd gear.

 

I know cause I've lost the governer gear before and driven 130 mile trip at 40 in second.

Turbo version you can do 55 with a little rpm left over.  Also governor failure, closer to home.

3AT at 3k rpms = 769.2 wheel rotations

 

5spd @ 3k rpms = 986.1 wheel rotations

 

216.9 rotation difference = 22% difference

 

 

3AT @ 5k rpms = 1282 wheel rotations

 

5spd A 5k rpms = 1643.6 wheel rotations

 

361.6 wheel rotation difference  = 22% difference

 

 

So you see, the ratios stay the same......22% taller gearing in the 5spd.......But the difference between the the gap at 3K and at 5K is almost 60% greater at 5k rpms.  Meaning you'll be going waaaay faster at 5k in a 5spd than you would in a 3AT.

NorthWet, on 29 Nov 2013 - 13:24, said:

The non-turbo 5MT vs 3AT seemed to be a couple 100 rpm difference... not so much as I noticed much or cared.

 

Ahh, this is way off. Assuming 23" tires, 65mph with the 3AT is 3900rpm vs the 5spd at 2900 for the same speed. A thousand RPM is a pretty noticeable difference. The 0.8 overdrive makes a big difference, plus no torque converter slip. The GrimmJeeper gear calculator is a handy tool for comparisons like this.

 

As far as top speed, it's power limited, not gear limited. At 100mph the 3at is 6k rpms vs 4500 with the 5mt, but either way the car isn't going to go much faster with 90hp. My SPFI powered wagon couldn't quite break 100 held flat out for an hour, but it was on 30" mud tires so it had a slight aerodynamic handicap. For pure speculation though the fastest a 3at could possibly go would be 125mph. The engine would be turning 7500rpm, but I know the valves don't float until 8.1-8.2k rpms so it could be technically possible. Maybe if it was drafting another car.

Gear calculations are all well and good... if you remember to factor in all of the ... ummm... factors.  Like transfer gear ratio.

Technically a 3at could hit 125? Lol wow. I've done 100 - 102 mph on the 3at and that was intense. The valves may float over 8k but the engine is gasping for air over 6500 so in my humble opinion I think the maximum speed you'd be able to hit would be about 105...110 tops. Who wants to try!? Lol

Haha, I don't know about top speed, but I can say this. At 60 MPH, I'm in 5th gear at 2750 RPM or so. Maybe a little more, maybe a little less. I don't remember. At 70-75 MPH, I'm in 5th gear at 3400 RPM. This is with a N/A EA82 and 5-speed D/R 3.9 ratio.

Ok cool. Thanks everyone. Now I won't be concerned about the engine exploding at those rpms lol.  I guess cruising at 70 on the highway will be ok then. What type of oil fo you recomend for these cars? i was going to put synthetic blend in it...

Ok cool. Thanks everyone. Now I won't be concerned about the engine exploding at those rpms lol.  I guess cruising at 70 on the highway will be ok then. What type of oil fo you recomend for these cars? i was going to put synthetic blend in it...

 

Yeah just remember that car was designed for when maximum highway speed nationwide was 55.

 

Type of oil not as important as how often you change it.  every 3k for regular oil, every 5k for synth.  Warning synth may leak more.

Gear calculations are all well and good... if you remember to factor in all of the ... ummm... factors.  Like transfer gear ratio.

If you mean final drive ratio, then both the non turbo 5spd and 3at have 3,9 final, so that's what I used. The 3.7 final 3at's from a turbo car wouldn't be quiet as high revving on the highway... they'd only be turning 3,700rpm at 65mph. So best case it's a 800 rpm difference between it an a 5spd. That's still easily noticeable.

If you mean final drive ratio, then both the non turbo 5spd and 3at have 3,9 final, so that's what I used. The 3.7 final 3at's from a turbo car wouldn't be quiet as high revving on the highway... they'd only be turning 3,700rpm at 65mph. So best case it's a 800 rpm difference between it an a 5spd. That's still easily noticeable.

No, I did mean the transfer gear.  The output from the planetary gearbox does not directly feed the rear driveshaft output.  It goes through a gearset that has its own ratio to consider.

No, I did mean the transfer gear.  The output from the planetary gearbox does not directly feed the rear driveshaft output.  It goes through a gearset that has its own ratio to consider.

The rear output is driven directly from the planetary output.

 

The front pinion has it's own transfer gearset.  Some models are 1:1, some are overdriven, but it's only .974 (38/39).  These models have a 3.7 front diff and a 3.9 at the rear.  Either way the rear diff is a 3.9

 

So the "final drive" of both diffs and the drivetrain as a whole is still 3.9 unless a turbo model.  then it's 3.7 front and rear.

Hmm, if I'm reading this correctly-

 

There are some 3AT's with a slightly different ratio?  Is there a way to know? 

 

I have a 1992 that turns about 4000 at 65MPH.  I also have a 1986 [in my 1987 body] - it turns a few hundred lower, and seems a little less peppy compared to the 1992.  My 1990 felt the same as the 1992.  I also had a 1988, but don't remember how it was, as my wife drove it mostly.