After reading LOTS of stuff here and on other forums, I decided to take the plunge and try getting the extra gear from a 545RFE working on my 45RFE.

I know that this works on 02-03 Dakota/Durangos but nobody could say for certain if it would work on on my 2000 model. Some said it wouldn't work at all and some said it might work but with a few problems.

I bought a refurbished TCM that was flashed with a 04 Grand Cherokee program. I didn't want to get my original TCM flashed in case it didn't work!

As soon as I started it up after fitting, all the gear selector lights lit up at once. This was one of the faults that had been mentioned that could happen. Driving it, everything felt ok. It was definitely different. The Torque Converter Lock-up Clutch doesn't operate till around 50MPH (I have 4.10's) but there was definitely a 6th gear!

Now in top gear the revs are the same as when I was running the original 3.55's, which is exactly what I was looking for. Later on the CEL came on and the code was P1698, which is saying a bad connection to the TCM but this was also expected. The final fault is the Overdrive On/Off switch no longer works.

As far as I know from reading all that I can on the matter, no damage is being done and I can live with faults I've listed. Until I hear otherwise, I shall continue to enjoy my "new" gearbox!

 

just don't pull anything heavy with your truck. doesn't sound like you can turn off your overdrive.

 

I occasionally tow a light (3800 pounds) 5th wheel caravan but rarely take that above 50MPH, I'm guessing it will stay in 5th at that speed, which I know it handles fine. It will be interesting to see if it tries to get into 6th at that speed with that load.

I've also fitted a high-stall converter with a upgraded, carbon-fibre lock-up clutch and a Sonex line pressure booster. Coupled with the 4.10 gears, I think I've got a pretty strong set up, BUT if it feels like its struggling at any time I'll make sure to take the old TCM with me and swap it over in a couple of minutes!

Thanks for your advice and concern.

 

Just an update on the 6th gear conversion.

Managed to put a few highway miles on it over the weekend. I'm very pleased with the extra gear. It has returned the RPMs at 70MPH to within 100RPM of where it used to be on the original 3.55 gears. I can live with the loss if the PRND21 indicator and Overdrive switch!

On the downside, once in top gear, its very reluctant to come out of it! With the old (45RFE) programming it would drop out of Overdrive when encountering even a modest incline at 70, which to be honest was a little too sensitive for my liking. Now you *******ly need your foot on the floor before it kicks down. I had expected this from reading comments on this mod in other forums but didn't realise it was quite so severe! This isn't really a problem for me, more of an observation but it might be a problem if you were thinking of doing this mod to a vehicle running 3.55's or even 3.90's. I think the engine would labour too much before kicking down.

I think I shall be putting the original controller back on when I'm towing my 5th wheeler but for solo running I really feel like I'm getting the best of both worlds. 4.10 punch for towing and acceleration and low RPMs for the highway, all changeable in 10min if necessary.

 

u tow a 5th wheel with your dakota?

 

Its the torque converter lockup. All I have to do in my durango is tap the brake with the accelerator down, and it kicks it out of lockup instantly. I dont know why it does, but thats how it works for me. Try it out.

 

I have the old TF type transmission, but mine does the same thing. Locked up in 4th, tap the brake, and it unlocks. Ride it a little harder and kicks back to third.

 

Yes sl2racer, I do tow a 5th wheel with my Dakota, but its only a little one! Its 21' and only about 4000 pounds loaded. I'm looking at a 26' which is about 4500 pounds, which I think it will handle happily judging by how it handles the 4000 pounder.

Moparman and Magnethead, Thanks for the tip about the Lock Up clutch, I shall try the brake tap next time! If that cures it, it will make a great mod even better!

Moparman, I see your Durango is a 2001, for which this mod is known to work perfectly. Mine is a 2000, and so runs with a couple of problems like the gear position indicator not working and the Overdrive switch disabled. I can live with both of those minor faults, I want to know if the P1698 code is a problem. I realise its because I'm using two different systems and they're not completely compatible but everything is working ok, should I be worried?

Thanks,
DakinUK

 

i have been wanting to put a 5th wheel setup on my truck but i wasn't sure how it would do with it. i just now hitch pulling 9-10k sucks and would imagine doing it with a 5th wheel setup would be a lot better.

 

The P1698 (No communication of TCM to PCM) is something I had about 6 months after I did the swap. I never had any problems with it, however I did spray it down with electrical connector cleaner. The code still hung around for a few months but it went away on its own. My shifting all worked like it was supposed to so as long as yours does too, I wouldn't be too worried about it.