AOD mods?
 

I have a rebuilt AOD in my garage. I have the stock converter, flywheel, cables, shifter, etc... Everything that I need to swap it into my car is there. The thing is, the trans is 1991 vintage, and completely stock.

I was thinking of putting in a good shift kit (trans-go?), and a loose converter (around 3000 RPM), and a good cooler, and calling it a day.

I know I could really bulletproof it, but I don't want to sink a ton of money in it. I might not like it, and switch back to a stick.

My car is also pretty light. (2750 lbs without me) so there will not be as much strain on the trans as there would be pushing a 3500 pound car down the track.

The next question is on rear gears. I have 3.73's with a 28" tire now, but was thinking of swapping in 4.30's.

Any opinions?

At least go with a one piece input shaft. That is probably the area most likely to fail on the AOD's. They are easy to change, and cost around $200.00 or less.

3.73's are a little weak with an AOD, 4.10s are a good street/strip compromise.

4.30s would be good with a 28" tall slick and Naturally aspirated, but wouldnt be much for highway or street cruising.

When installing a one piece input shaft, do I need to use a specific converter for a one piece shaft? And I put the 4.30's and a 28" tire through the analyzer, and in 1:1 gear 6000 rpm is only around 114 mph. I guess it's the 4.10's.

Also, what are the advantages/disadvantages of lock-up versus non-lockup?

I think a one-piece input shaft requires a non-lockup converter. The factory converter locks up using the extra input shaft. So no extra input shaft, no lock-up.

Advantages- its stronger, and you still have torque multiplication in 3rd and 4th gears. The factory AOD locks up in 3rd and 4th and kinda falls flat on its face when it does it.

Disadvantages - slightly worse gas mileage and higher cruising RPM.


Theres also a school of thought that a lock up converter can give you a higher trap speed, but I dont really know much about it. I think that might help in higher horsepower applications.

I don't know for sure, but I think it might be true.

I have a 3000 rpm lock up converter, and it great off the line. Gets the car into the powerband very quick. It's also great from a roll up to about 45 mph, when you punch it the tranny drops down and the cars picks up very quick. At highway speeds when the converter goes into lock up mode, it doesn't feel as quick. Just cause of the fact the converter isn't slipping and keeping it closer to a 1 to 1 ratio. Its great on gas, but i still wish i had bought a non lock up converter, for performance reasons.

Also you might want to look into getting a remote trans filter after you mod the tranny. When hooked in line the filter can save your tranny if you converter decides to let go. You won't have any of the converter parts getting flushed back into the trans, they would be stuck in the filter.

I've talked with some experienced racers who agree that you can actually trap faster at the big end of the trap with a locking converter. It gives you a direct connection from the motor to the tranny without using up power in converter slip and heat. At those speeds and rpms, you're already in the powerband of the motor and likely past the stall speed of the converter anyway, so the converter slip is not needed and simply uses up power.

I like the non lock-up for the street. It does make more heat and gives slightly less gas mileage, but it does allow torque multiplication in all gears, and it saves your tranny the "hit" experienced when a locking converter locks up. I've really enjoyed my PI non lock-up.

As far as a shift kit goes, you're going to end up spending somewhere around $100 for a shift kit. You might consider spending a bit more and getting a Lentech valve body. They are really nice units, and I've had many people tell me that they wish they had gone with the full valve body to begin with rather than doing the shift kit. Some even say it was the best mod they've done. It goes a long way to bullit-proof the tranny. There are guys out there running stock AOD's with a PI converter and a Lentech valve body running well into the 10's in the 1320 for over 3 seasons with no problems. It eliminates the need for the 1-D-1 shuffle and pretty much eliminates the problems with OD breakage. I paid $414 delivered to my door and fully customized for my car. It shifts 1-2-3 with electronic OD delete at the push of a button. I'm installing in two weeks and will let you know how it goes. From all I hear, the vb shifts upon command without the typical delay seen in AOD's, and it shifts depending on how you tell them to set it up.

Hope that helps.

--nathan

I cant understand why Lentech needs an "overdrive delete" button. Can someone clear this up for me? The AOD will not shift into OD under full throttle. It will only go to third, and then when the throttle is closing, it will shift into OD.

When I spoke with Lentech on the phone, the guy told me that they did this so it wont shift into OD under a full load or heavy throttle conditions, which OD cant handle, thus the "switch" giving you manual control of OD. This simply isnt necesary, and is a complete turn off for me. Who wants to drive around on the streets having to flip a switch every time you want 4th gear? With 4.10s in the rear, your going to be doing quite a lot of flip switching. And I believe if you forget to switch it back after you downshift, it can lead to problems. No thanks

My valve body has a 1,2,3-4 shift pattern and has no need for a "switch" to control overdrive. Lentech invented the valve body modification to change the shift pattern, so you think they would know what their doing?

Go figure....

Mach 1,

As far hitting OD under WOT, my tranny is having this exact problem. I'll be cruising the 1320 fine until I hit about 4500 in third and the tranny would drop into OD even with the tranny held in D...effectively killing my times and using up my OD. However, I don't believe this is suppose to occur.

If you simply leave the OD switch on and put the shifter in the OD position, the tranny will shift automatically anyway, so you don't have to flip a switch every time you want OD (as long as your TV linkage remains hooked up). But you can lock it out when you don't want it.

I think Lentech designed the feature more to allow racers to lock out their OD. That way, even at the end of the track where you let off the throttle, the tranny won't shift into OD. As I have 3.73's, I don't use the OD until I'm up to speed on the highway. In fact, I always drive in D when in town to save the tranny from shifting needlessly into OD and back into third everytime I hit 35-40 mph in town and then hit the gas. This avoids extra wear on the tranny.

I do think that Lentech has a nice product, however. I'll let you know how it performs when I get it bolted to the car.

--nathan

No, thats not supposed to occur. I originally though my valve body was "modified" to prevent this from happening, but since have researched that it should be that way from the factory.

I dont see the need or advantage of that? Why not shift into OD at the end of the track when you let off the throttle?

Here is my experiences with this situation. If you buy an Art Carr one piece input shaft you will have to have an Art Carr converter. I have a PI solid shaft and it will work with any convertor.

Convertors.. I had a B&M holeshot(when stock) and thought it was a good unit(B&M shift kit at the time). I bought a lockup PI convertor after the engine change and was miserable. The car ran like ****. PI said it was a tuning problem but would refund my money. I sent it back and had it recalibrated to a 2800(from 3000) and non-lockup(one time free change with purchase) and added a lentech valve body at the same time(at the suggestion of lentech) and all I can say is WOW. The car is sooo much faster(seat of pants) and runs better than before. Gas mileage, slightly worst with a non-lockup?? *cough*BS*cough* I hardly drive the car lately because of the gas mileage(couple other reasons too though). Big difference in gas mileage.

I couldn't be happier with the lentech unit. I hardly ever use od around town anyhow, if you do you have/will have a problem anyhow. Using od around town will cause the od to burn out. The Lentech unit will allow you to hold any/all gears to whatever rpm you want and that makes one hell of a big difference.

Mach1, it will shift into od at full throttle after a certain speed. I like to have control of what the car is doing and I appreciate what the Lentech unit alllows me... an auto/manual tanny.

Thats funny, Ive been driving around town in OD for over 4 years and never burn it out. And I spend most of my time in OD, with the 4.10s, and left in automatic shift mode, it gets into overdrive fast. I would say within 50 yards.

I have to totally disagree with the dont use overdrive in town "theory" and have personal experience as proof. Has anyone actually burn up overdrive by using it around town, or are you just repeating what you read somewhere? If your tranny is in good shape, there no reason OD wont hold up with normal street use. After all, thats what its there for.


What speed is that? I go through the traps at over 105 mph and still hold third. I have total control of all shift points and I have absoluetly no need or reason for a switch to lock out overdrive.

I've had this car since 1991 and the aod has been built twice. The first time ws because the od was burnt(in 94), supposedly because I left the car in od while running around town. The second time was the performance build.

If I didn't have experience with it I wouldn't have said a thing about it.

Your OD was burnt out because thats one of the weakest links in the AOD and usually the first thing to go. Does this mean you shouldnt use it around town? No, I dont think so. It was designed to be used around town and you didnt do anything wrong by driving it that way as you were implying. Of course you could drive around in first gear all the time, and 2nd, 3rd and overdrive would never wear out, but thats up to you.

I use my overdrive and prefer the lower cruising rpms that come with it.

To say using overdrive around town will cause it to burn out is not an accurate statement.

Hey, if you want to use your OD around town, that's fine. And if myself and rbatson don't, that's fine, too. I understand our setups are different, and if I had 4.10's, I might choose to do the same as you do.

However, with my setup, with the car in the OD position, the tranny will shift EARLY from third into OD...say around 35-40 mph. This is the cruising speed on many larger streets. That's fine if I'm going that speed for a long time. However, as it is, I have to slow down, then speed up, then slow down, etc. for traffic and lights. When my tranny shifts into OD at that speed, it becomes sluggish and doesn't respond well. So when I step on the gas, the tranny usually drops back into third.

I don't think it's the cruising in OD that kills the tranny, but rather the frequent downshifts into third which are hard on the OD band. For instance, many people lose their OD after cruising on the highway in OD and then accelerating hard, causing the tranny to downshift into third. I choose to simply lock out the OD to avoid this shuffle back and forth which does wear down the OD band.

I don't know why Lentech designed the VB that way, but it works, and it's a quality piece of work. It's a fully automatic valve body with manual shifting capabilities, and that's just what I need.

--nathan

Actually, I believe od was designed for highway use. 'Around town' and 'in town' mean the same thing to me, stop and go traffic and less than 45 mph. This puts alot of unnessary wear and could cause od to burn prematurely, it being a weak link is just describing the cause. Lentech doesn't advise using od if going less than 45mph. Your gears may/may not make alot of difference, I couldn't tell you that. I had stock gears when mine burned.

You can cetainly drive your car however you like, I'm just stating my experience with owning an aod for 11 yrs.

I dont think an AOD with stock gears will shift into OD until 45 mph anyway? Am I wrong?

When mine was stock in would shift into OD around 45-50mph

Thats what I thought. These guys driving around in third because they "afraid" of destroying thier AOD arent doing anything except wasting gas and putting more wear and tear on thier engine.

Gimme a break!
 

C'mon Mach 1. Does it look like I have stock gears?? Yeah....I'm just some little chickensh*t who is scarred to drive in overdrive....OHHHHH....NOT OD......I'M SCARRRREEEEDDD.

It's been a long time since I had stock gears, and most guys with AOD's have long since upped to 3.73's or 4.10's. Turning those rpm and depending on how they've got the TV adjusted, OD comes much earlier than it normally would. I know from MY experiences, shifting back and forth into OD while cruising around town is NOT what I want to happen. It takes me completely out of my powerband, and if I need to accelerate, I have to wait for the tranny to downshift into thrid before I can do much. Anyway, this argument has gotten a little out of hand over nothing. If I want to drive around "wasting gas and putting more wear and tear on thier engine" *cough cough BS*, that's what I'll do. If you want to drive around in OD in town....go for it. It's your car and you can do as you wish.

I'm out.

--nathan

Man, no reason to get upset over this simple discussion. Im just putting the facts as I know them on the table.

If you have higher gears, 3.73 or 4.10, and you go into overdrive quickly because of this, you should stay in overdrive. I dont know why your tranny would shift back and forth while driving around town? Mine doesnt do this and I have had no problems with "excessive" back and forth shifting.

I do live in a flat area though, and I guess if you were driving in a hilly area, this might happen more often.

Out of your powerband...*cough, cough, BS*, one blip of the throttle and you should downshift to third or second, depending on how fast your going and what gear your in at the time, automatically , and be right back in it.

Maybe your engine is a dog?

If your that worried about being out of your powerband and burning up overdrive, suit yourself.

I never said you couldnt drive that way. Im just saying I think people overeact about he "shifting back and forth" thing, and you are a perfect example.

How is wasting gas and more wear on your engine bullshit? When you drive around in a lower gear and turn your engine at a higher RPM, this is what happens. Can you please explain your remarks? Oh, maybe your full of BS yourself?

Mach1, I would usually give my opinion and if someone disagrees then let them voice their opinion and let the original poster come to their own conclusion. I can't help myself in this one though..

Where I live there is a stop light every block-- block and a half, you get up to speed(about where od will hit) and you have to slow down for the light. I'm not burning anymore gas by staying in 3rd because I can't stay in od long enough to get any benifit from it. Yes, it puts wear on the od by shifting back and forth and you are surely the man to make the call on your car, I will continue to drive mine as I know the situation and the way the car is supposed to be driven.. I know by driving around town in od would cause the need for a rebuilt. You say yourself that od is the weakest link so why in the world would you want to shift back and forth with it every time you go for a ride??

I think you need to rethink your logic on this one.

Yeah, overdrive is usually the first thing to wear out in an AOD. This is true. Does this mean you shouldnt use it? I dont think so, and I explained my reasoning.

The way my car drives, I dont have a problem with excessive shifting. I get up to fourth gear, and when I stop, I start over again in 1st gear. Pretty simple, it works fine, this is the way the car is designed to run, and Im still turning high enough RPMs in 4th gear where I have plenty of power (if not, the car wouldnt shift into 4th gear in the first place) and I have not prematurely wore out my transmission by doing this.
Keep in mind I have a modified transmission with high performance clutches and a non-lockup converter and maybe this is the difference? My car gets into 4th gear quickly (4.10's) and driving around in third would negate the benefit of having an overdrive gear in the first place. If I was that concerned with it, as some of the people here are, I would just get a C4 or a manual.

If you have different circumstances, suit yourself.

I just dont agree with leaving the car in third because of fear of 4th gear burning up. I dont think the AOD's are that fragile to be concerned with it, and I think people who are leaving the car in third gear are overracting to this fear.

Thats my opinion, and my logic is sound. Try it, you might be surprised. Are all you guys still running lock up converters? The more I think about it, the non lock up converter versus the lock up converter could make the driveability of our cars different, and may by why I have different results than others?

Later

I'll try this one last time.

I live in a town, like rbatson, that has frequent stoplights and a lot of traffic. If I leave the transmission in OD while driving in town, the tranny will shift into OD at every opportunity it gets...usually around 35 mph. At this speed, OD pulls the revs down low...like around 1500. My power band begins right around or just below 3000 rpm. When the car shifts into OD at this low of an rpm, it puts a heavy load on the motor and gives the sensation that the motor is bogging.

As it is, in this type of traffic, I usually don't have opportunity to cruise at 35+ mph for very long as someone is always slowing down traffic. As soon as I drop my speed, the car shifts back into third gear. Then, when I get a clear lane and step on the accelerator lightly to pick up some more speed, the tranny shifts back into OD at 35mph and bogs the motor. This scenario happens all the time. It's a constant thing here until I get out of town. Thus, on a typical commute, there are many shifts back and forth from OD to third. I choose to leave the car in D to avoid this.

I don't see this as using up much, if any, extra gas, and it doesn't place unneccessary load on the engine. In third gear at the speeds I see in town, I may push 2000-2500 rpm. The engine likes this speed much better than the lower rpm's seen in OD. It is more efficient at these rpms and higher, and as it is more efficient, it decreases the workload felt by the engine. As far as wear, if my engine experiences excessive wear at 2000-2500 rpm, then I've got a problem.

Who knows...maybe I would see a SLIGHT increase in gas mileage by using OD in town. But I would also see increased wear on an OD band that was slipping when I bought the car. Since I have been avoiding OD in town, manually shifting the car into OD once appropriate highway speeds are reached, and manually downshifting into third when decelerating, the slip has abated.

I understand that you have a built transmission, and you have had no problems using OD in town. My transmission has been rebuilt twice (before I bought it) and is stock other than a non lock-up PI converter and a Transgo shift kit which isn't working like it was designed to.

My engine is not a dog; my transmission is a dog. That's why I've spent so much money to make it run like it should. That is why I'm purchasing the Lentech valve body...to correct problems that have been plauging me for a long time. I resent your slight to my engine, and I'll have to ask my car to forgive you as it has very sensitive feelings :( .

No, I'm not full of BS, and I didn't imply that you were, either. I'm not paranoid or overly scarred. I'm simply doing what I know works and what I have had success with for three years in keeping a tired transmission running. When it goes, I'll get it built right. Until then, I have to be a sparring as possible on the OD.

If you've had success using OD in town...more power to you. I've had succes in not using it. I'm not saying your logic isn't sound. It's as sound as my logic, and I can agree with it. However, on my car, this is what works best. I've tried my best to explain myself, and I don't know what else I can say.

--nathan

I got the same prob silver. I think its the 4.10 gears. Anyway I plan to upgrade to the lentech VB after i finish my current project. Besides Ive never ran OD in the city unless I can stay at 45+ for a while. OD is for the highwaqy