auto tranny mod
07-28-2010, 11:19 AM
#1
Registered User
Thread Starter
Join Date: Jul 2010
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
auto tranny mod
In searching for a tranny problem I saw that the A340 is basically a Jeep AW4.
There's a great mod to lock your tranny in 1st or 2nd to get true 4 speed shifting. If there's any interest I'd be glad to give a description and diagrams. It's not real difficult and you'll never curse at that sudden downshift into first when you don't won't it to. If this has already been posted and I just couldn't find it, apologies in advance.
Bob K
There's a great mod to lock your tranny in 1st or 2nd to get true 4 speed shifting. If there's any interest I'd be glad to give a description and diagrams. It's not real difficult and you'll never curse at that sudden downshift into first when you don't won't it to. If this has already been posted and I just couldn't find it, apologies in advance.
Bob K
07-28-2010, 01:56 PM
#2
Registered User
Join Date: Jun 2006
Location: Ocean Springs, MS
Posts: 262
Likes: 0
Received 0 Likes
on
0 Posts
Post a write up on it. It will help someone. I have used the solenoids out of jeeps with the aw4 in a toyota auto. Lots of them in junkyards so they are cheap...
07-28-2010, 03:35 PM
#6
Registered User
Thread Starter
Join Date: Jul 2010
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
tranny mod
Ok here goes. This is not original but I have made it simpler and a bit different from the original.
Biggest problem w/ the tranny is no real control over 1st and 2nd. This mod lets you lock the tranny into 2nd gear. Great for coming down a hill, especially with curves. You've downshifted into L to control your speed and all is great. Then you come up to a curve and want to slow down a bit, but bam it slams into 1st. So you up shift back to D to get out of 1st, speed up and then down shift into L again to get back to 2nd. I always hated this tranny until I did this mod, and now I love it.
The key is to control tranny solenoid 2. The tranny gear is controlled by S1 and S2 as a matrix. S1 on, S2 off-1st gear. S1 on and S2 on-2nd gear. S1 off and S2 on- 3rd gear. Both S1 and S2 off, and OD on-4th gear. If you use page AT-63 out of the manual as a reference you can easily see what I'm doing. In the L position, only 1st and 2nd gear is possible. 1st gear is only possible if S2 if off. The solution is to keep S2 on, then you only have 2nd gear.
So basically all you have to do is provide 12v to S2 to keep it locked into 2nd gear. This is done by tying the 12v from L (12v when the shifter is in the L position) to S2 thru a switch and a diode. By using the 12v from L, it only has any effect if you are in the L position. Otherwise, if you use 12v from somewhere else and forget to turn it off, you couldn't shift into 4th when in the D position. (S2 must be off for 4th) The diode (in the direction from L to S2) is to keep S2 from back feeding L when your in D and forget to turn the switch off. Another diode is used at S2 to keep this 12v signal from back feeding the ECM.
It really works great and the only downside is if you forget to turn the switch off and your shifter is in L and come to a stop, you will be starting off in 2nd. Not a big deal.
Bob K
Biggest problem w/ the tranny is no real control over 1st and 2nd. This mod lets you lock the tranny into 2nd gear. Great for coming down a hill, especially with curves. You've downshifted into L to control your speed and all is great. Then you come up to a curve and want to slow down a bit, but bam it slams into 1st. So you up shift back to D to get out of 1st, speed up and then down shift into L again to get back to 2nd. I always hated this tranny until I did this mod, and now I love it.
The key is to control tranny solenoid 2. The tranny gear is controlled by S1 and S2 as a matrix. S1 on, S2 off-1st gear. S1 on and S2 on-2nd gear. S1 off and S2 on- 3rd gear. Both S1 and S2 off, and OD on-4th gear. If you use page AT-63 out of the manual as a reference you can easily see what I'm doing. In the L position, only 1st and 2nd gear is possible. 1st gear is only possible if S2 if off. The solution is to keep S2 on, then you only have 2nd gear.
So basically all you have to do is provide 12v to S2 to keep it locked into 2nd gear. This is done by tying the 12v from L (12v when the shifter is in the L position) to S2 thru a switch and a diode. By using the 12v from L, it only has any effect if you are in the L position. Otherwise, if you use 12v from somewhere else and forget to turn it off, you couldn't shift into 4th when in the D position. (S2 must be off for 4th) The diode (in the direction from L to S2) is to keep S2 from back feeding L when your in D and forget to turn the switch off. Another diode is used at S2 to keep this 12v signal from back feeding the ECM.
It really works great and the only downside is if you forget to turn the switch off and your shifter is in L and come to a stop, you will be starting off in 2nd. Not a big deal.
Bob K
Trending Topics
07-28-2010, 05:13 PM
#8
Registered User
iTrader: (1)
Join Date: Nov 2006
Location: Clarkston,WA
Posts: 363
Likes: 0
Received 0 Likes
on
0 Posts
Manual control
In searching for a tranny problem I saw that the A340 is basically a Jeep AW4.
There's a great mod to lock your tranny in 1st or 2nd to get true 4 speed shifting. If there's any interest I'd be glad to give a description and diagrams. It's not real difficult and you'll never curse at that sudden downshift into first when you don't won't it to. If this has already been posted and I just couldn't find it, apologies in advance.
Bob K
There's a great mod to lock your tranny in 1st or 2nd to get true 4 speed shifting. If there's any interest I'd be glad to give a description and diagrams. It's not real difficult and you'll never curse at that sudden downshift into first when you don't won't it to. If this has already been posted and I just couldn't find it, apologies in advance.
Bob K
07-29-2010, 07:37 AM
#9
Registered User
Thread Starter
Join Date: Jul 2010
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Yeah, the systems you sell are really nice if you want to go all the way with full manual shifting for your auto. I was just showing a way to control 1st & 2nd gear easily and cheaply. I just thought this might appeal to a lot of autotranny owners.
Bob K
Bob K
07-29-2010, 08:14 AM
#10
Registered User
OH! This is real interesting. I had no idea this type of thing even existed. What I'd be interested in is making 3rd gear a bit taller or 4th (O/D) a bit lower. IOW, somehow ease the transition between those two gears. What I don't particularly care for about this transmission is that big jump. Example: driving in O/D with CC on, most of the time on inclines (depending on the grade) the 4rnr will lose momentum in 4th and drop into a lower gear causing the motor the rev way up. So, at hills like that I have to tap the brake to knock out CC and use the accelerator to keep it from dropping gears like that.
07-29-2010, 06:55 PM
#11
Registered User
iTrader: (1)
Join Date: Nov 2006
Location: Clarkston,WA
Posts: 363
Likes: 0
Received 0 Likes
on
0 Posts
Info
07-30-2010, 07:05 AM
#12
Registered User
Thread Starter
Join Date: Jul 2010
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Yeah I get that. The point is I didn't see it on THIS forum and I thought it would be worth bringing it up. It's a great mod and it seems not everyone has heard about it. I thought that's what this forum was all about-to get and give info and help.
Bob K
Bob K
Thread
Thread Starter
Forum
Replies
Last Post
Iceman4193
86-95 Trucks & 4Runners
3
07-15-2015 04:48 PM
