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CrazyInside

New Member
Feb 10, 2012
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Oregon
I have a 91 turbo auto car that I just swapped to a 5 speed. When i'm driving the rpms seem way higher then they should be? In 5th gear at 60mph i'm at like 3100rpm, 4th gear at 40mph is 3000rpm, does this seem high compared to cars that came 5 speed? Or maybe my auto tach doesn't register right? But if defiantly seems to be at 3k rpm at 60mph.
 

Dirgle

Conjurer of Boost
Mar 30, 2005
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Pauma Valley, CA
You would be correct. The proper RPM for a 91 turbo with an R154 is 2272RPM's at 60MPH. A couple of questions.

How are you measuring MPH?
Where did you get the R154 from?
Are you running factory size tires?
Are you sure that the original diff is in the car?
 

MarkIII4Me

Project OVERKILL!!!
Apr 10, 2005
1,249
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Charleston, SC
Same thing happened to me. In my case the r154 came out of an early MKIII and I didn't know at the time to swap the little plastic speedo gear that goes in where the speedo cable connects into the trans. As a result, my speedometer is around 10% lower that what I'm actually doing. So the tach looks like it's reading higher than is should when in reality it's the speedo that's off. If I wasn't using my gps one day, I probably would have never noticed how much slower the speedometer was actually reading.
 

IndigoMKII

New Member
May 9, 2011
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Madison, Virginia
If he got the transmission from a 88-92 turbo car, it'll be set for the 3.73 rear gear speedo gear already. If he got the transmission from a 87-88 turbo car, it'll be setup for a 3.91 speedo. You'll need to swap over the entire speedo assembly IIRC because the gears from transmission to transmission have a different degree to the gears themselves.

But there is a lot of questions that need to be answered to accurately answer this question.
 

Dirgle

Conjurer of Boost
Mar 30, 2005
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Pauma Valley, CA
Changing speedos won't make a difference, as most toyota speedos calculate speed based on 1026revs=1mile. So speedos from all years read the same unless they have worn out and are out of calibration. Which is a different story. Also speaking of the speedo gears in the transmission. There are two of them, a driven and a drive gear, and they both have to be changed to match whatever your final drive ratio is in your differential.