Best TSB ever.

So, I was poking around for information on Janel's 2000 Grand Cherokee when I came across a bit of info that just seems too odd to be true. You can add an extra gear.

The 45RFE transmission is actually a five-speed pretending to be a four speed, using an alternate second gear when downshifting. For 2001, Jeep changed the transmission and used six ratios in the box, again with an alternate second gear. They called this the 545RFE, and it's mechanically identical. The only difference is in the programming of the transmission control unit. There was actually a TSB released by Jeep for hard-shifting trucks that had the side effect of converting a 45RFE to a 545RFE. Yes, you'd bring your four-speed automatic Jeep with complaints about rough shifting and you'd drive home in a five-speed automatic Jeep later that day.

Now that is cool. I really don't know how automatic transmissions work, and now I know even less. But I'm tempted to drop by the Jeep dealer and get an extra gear added for 1 hour of labor.

That's got to be one of the dumbest things I've ever heard...So naturally being a Chrysler product, I have little reason to doubt its plausibility.

In reply to Driven5:

Yeah, the dumb thing being they incurred the cost of producing a 5 speed, but didn't make it a 5 speed to begin with.

They are just engaging OD after 2nd to make a new 3rd gear and move the other gears down a step. Too many soccer moms were spilling their overpriced coffee when going around town chasing down their obnoxious and ill-behaved crumb crunchers.....

This is just like the "new" 6X trans you can buy from TCI. All it really is is a GM 4L80E with a fancy control box to engage OD after 1st and 2nd gear to take it from 4 speeds to 6. Nothing special.

For a second there, I thought this was going to be like the Healey 100 where first was blocked off because it was deemed too low. (it was).

Hahaha they charge you more for unlocking the 5th gear, I thought only software vendors did that crap. Still, more good stuff for us in the know!

Driven5 wrote: That's got to be one of the dumbest things I've ever heard...So naturally being a Chrysler product, I have little reason to doubt its plausibility.

Everyone does it.

I have a little JR50 mini-bike that was a one speed from the factory. I found out through looking at a mechanical drawing for the gearbox (and the internet) that the bike actually has a two speed transmission.

All you have to do is grind a little bit of the shift mechanism and voila! 2 Speeds!

Please enter your validation key code for 5th gear.

sachilles wrote: Please renew your subscription for 5th gear.

FTFY.

Same thing Ford did to the 4R100 to make it the 5R100, just engage OD in second gear to get the extra "gear". Not necessarily a bad idea, especially if the rpm drop from 2nd to 3rd is on the wide side.

The 62TE is the same way, it's a six speed sort of, it has a passing gear. I actually really like that idea.

GameboyRMH wrote: Hahaha they charge you more for unlocking the 5th gear, I thought only software vendors did that crap. Still, more good stuff for us in the know!

Actually, it was done under warranty. Not that you'll find one of these still under warranty, but the TSB was issued in 2001.

It's not just engaging OD on an intermediate gear, either. The top gear changes from 0.75 to 0.67. You can tell if this reflash has been done by checking the engine rpm on the highway. According to our tach, we still have a four speed (which uses five ratios) instead of a five speed (which uses six ratios).

Apparently (according to Wikipedia) the trans has three planetary gearsets in it instead of two, so I guess it makes sense that it would have 6 speeds instead of just five. Not really sure you could make a five speed in that case. But still, that's weird...

And this is why my SUV has a stick! This proves that automatics run on voodoo magic and eat souls.

GameboyRMH wrote: Hahaha they charge you more for unlocking the 5th gear, I thought only software vendors did that crap. Still, more good stuff for us in the know!

I went straight to the stories of printers that are mechanically identical at three price points, but are hamstrung by code that slows them down at the lower price points...

In reply to ransom:

I've known more than one dealer to hack printers/copiers to make them run at the fastest speed.

It's not that well known in the US where all MINIs are Coopers, but in the UK there was one called the MINI One. It was the non-Cooper inexpensive model with a lower power rating. The successor to the original intent of the original MINI, you could say.

Tuners quickly discovered that it actually had the same engine as the Cooper. The only difference was that the throttle plate didn't open all the way. Since it was DBW, a quick software flash took care of that little problem and added 25 hp.

Keith Tanner wrote: It's not just engaging OD on an intermediate gear, either. The top gear changes from 0.75 to 0.67. You can tell if this reflash has been done by checking the engine rpm on the highway. According to our tach, we still have a four speed (which uses five ratios) instead of a five speed (which uses six ratios). Apparently (according to Wikipedia) the trans has three planetary gearsets in it instead of two, so I guess it makes sense that it would have 6 speeds instead of just five. Not really sure you could make a five speed in that case. But still, that's weird...

A 545/45RFE should still only have two planets in it. The 68RFE has three total planets with the addition of the 2/4 clutches and additional planet for the gear reduction. I am staring right at the transmission parts schematic which covers all three transmissions.

I don't claim to be a transmission expert, that's what the Wikipedias say about the trans. Whatever's ever going inside that devil box, I'm still going to get an electronic update for a bonus top gear

free prize in every box

(well, almost free)

Driven5 wrote: That's got to be one of the dumbest things I've ever heard...So naturally being a Chrysler product, I have little reason to doubt its plausibility.

This.

Keith Tanner wrote: It's not that well known in the US where all MINIs are Coopers, but in the UK there was one called the MINI One. It was the non-Cooper inexpensive model with a lower power rating. The successor to the original intent of the original MINI, you could say. Tuners quickly discovered that it actually had the same engine as the Cooper. The only difference was that the throttle plate didn't open all the way. Since it was DBW, a quick software flash took care of that little problem and added 25 hp.

talk about raising the bar on bullE36 M3. next thing you know they'll be simulating engine noise in the passenger compartment.

I figured this was a belated noticing of this........still the most awesome recall/tsb in existance.

OK, I'll bite: there was a tsb because of flames shooting out of the exhaust? Tell me more!

Oh, and for Keith: I once read (in a book about the development of the 3rd-gen Taurus) that the chief auto trans engineer at Ford had a sign in his office that read, "You do not want to know how an automatic transmission works."

When about to graduate college, I took a tour of a Kawasaki plant that primarily made mower and other non-automotive engines. I was told by the engineer (who I knew from school...he graduated a semester prior) that in many cases, the difference in power rating on a line of engines was simply the throttle opening/stop (much like the Mini example above).

I know first hand that in todays manufacturing environment...it doesn't always make sense to tool up for a different product at lower specs. It often is better to just de-rate an existing product with a new catalog page and load rating sticker.