88 ranger 2.9l 5spedd manual transmission high rpms

[JohnO]

I have a 88 ranger 2.9l 5 speed manual transmission I just got the truck drivable after new clutch, water pump, radiator, thermostat. I drove the truck to work the other day and I noticed the rpms were really high. I was running 4,000 rpms at 65 in 5th. I've been told that the gears in my rear end may be the wrong ones. But i thought i would ask around before i started buying new parts. It feels like the truck runs through the gears really fast without the gain in speed. Thanks in advance

 

[rusty ol ranger]

Sure your new clutch isnt slipping?

If someone regeared it yes that would cause that, but youd have to have really, really, outlandish gears. Like, 4.56's.

It doesnt have really really tiny tires on it does it?

 

[JohnO]

It doesn't feel like its slipping. I have 215/70R15s on it right now

 

[rusty ol ranger]

Get up to about 15mph in 2nd or 3rd gear, drag the brakes and get into the skinny pedal, if the engine speeds up quicker then it should you got clutch issues.

Theres no other reason.

Is this a 2wd or 4wd?

 

[JohnO]

2 wd

 

[JohnO]

I bought the truck about 2 months ago and I was told that the tranny was supposedly been rebuilt. Not sure how true that is

 

[Paulos]

Compare the axle code and the trans code on the sticker inside the drivers side door, to the codes on your trans and axle to make sure they match. The Tech section here at the Ranger Station will tell you what is what if you have the codes.

 

[rusty ol ranger]

Compare the axle code and the trans code on the sticker inside the drivers side door, to the codes on your trans and axle to make sure they match. The Tech section here at the Ranger Station will tell you what is what if you have the codes.

Theres no ranger trans/rear end that came from the factory with gears low enough to cause 4k@65mph.

Im assuming youre running a factory tach...is it possible its malfunctioning? Or does it really sound like its turning 4k?

 

[JohnO]

Theres no ranger trans/rear end that came from the factory with gears low enough to cause 4k@65mph.

Im assuming youre running a factory tach...is it possible its malfunctioning? Or does it really sound like its turning 4k?

Its really running that high almost everything about the truck is factory

 

[Paulos]

Theres no ranger trans/rear end that came from the factory with gears low enough to cause 4k@65mph.

Im assuming youre running a factory tach...is it possible its malfunctioning? Or does it really sound like its turning 4k?

It depends on the trans. If someone took an auto trans out and replaced it with a manual trans without changing the rear diff.... If it was the clutch it would be obvious. That only leaves gear ratios and tire size. I would check the stock tire size on the sticker also, to see if it came with those 70 series tires.

 

[Bird76Mojo]

I can't see where a set of 215/70R15 tires would be so different from the factory size tires on that truck to cause that kind of highway RPM. From a (195/70-14") 24.7" tire at the smallest factory sizing, to what he's running (215/70-15") being 26.9" - That an 8.9% difference in diameter. About 60 less revolutions per mile.

In fact, him going with larger tires than stock would drop his highway cruising RPM. Even with his size of tire (a 27" tall tire) and guessing that he could have a 4.56 rear gear, he should still only be turning around 2500rpm or so at 55mph. A 3.73 rear gear would have it turning around 2000rpm at 55mph. Even with a 4.56 rear gear and his 215/70-15" at 65mph his engine speed in OD/5th should still be around 2900rpm.


The OP mentioning the truck going through the gears really fast without much change in speed, and the high revs on the highway, leads one to think it's got some extremely low gearing in the rear axle.

Tire Rack and several other sites list the following as available factory/optional sizes on his 88 2wd:

1. 195/70R14
2. 205/70R14
3. 215/70R14

Of course, with tire size differences, this could potentially add to the confusion, as it will cause the speedometer to be off. So he thinks he's running 65mph and he's not.

Makes me wonder what the true engine RPM really is at highway speed. Also makes me curious about the clutch..

 

[rusty ol ranger]

It depends on the trans. If someone took an auto trans out and replaced it with a manual trans without changing the rear diff.... If it was the clutch it would be obvious. That only leaves gear ratios and tire size. I would check the stock tire size on the sticker also, to see if it came with those 70 series tires.

Auto trans rangers had the same selection of rear gears as the manuals.

OP jack the truck up, mark the driveshaft, then spin it by hand and count how many times the shaft rotates before the axleshaft makes one revolution. Thatll give you an idea of your rear gear.

But assuming you got the stock 7.5 rear a 4.10 is as low as it gets.

 

[Paulos]

When I was much younger, I had a Chevy Vega with a 4 speed manual trans. I found another Vega with a really nice body and interior, but it had an automatic trans and a bad engine. I swapped my motor and trans into it and failed to consider the rear end before I got it running and got rid of my old Vega. Needless to say, that lower ratio rear end didn't work very good with the 4 speed. It was just the opposite effect of what JohnO is describing. If a previous owner took out an automatic trans and put in a manual trans without changing the rear end or ring and pinion it would run like he describes. Using 70 series tires instead of stock 75 series tires would make it a little worse. The ratios in the ranger diffs range from 3.08 to 4.10, and my experience is the lower ratios were used with automatics.

 

[rusty ol ranger]

But even with 4.10s and 70series tires he shouldnt even be knocking on 4000rpm at 65.

The bottom line is theres a problem here, and not just a spec problem.