My 89 F150XLT Lariat has a C-6 Trans. My Gear selector says P,R,N,D,2,1.
When it shifts ok from 1 to D but the engine seems like it wants to shift into OD after in D / 3rd ? for a while but it does not have OD by the code (K)
It does not have a tack so I do not know how many RPMs it is going when at 55MPH but seems to be screaming >

Any suggestions, help ?

 

Go under the truck, count the trans pan bolts.

17 = C6
14 = AOD
20 = E4OD

Nothing can be taken at face value on a near 40 year old vehicle, sure if you owned it since new maybe. Asking about OD on a C6 makes no sense

EDIT Note the AOD never came stock behind a 351W, but holds up fine if swapped. Unsure about 4.9 trucks, guessing C6 and E4 only options in 1989.

 

FIFY

Ford DID use the AOD behind 351W in cars. More exactly in 351W-police package cars. The AOD in my '89 Crown Vic is still there behind its 380hp 351W-stroker 393W - now 615hp 395W... Oh, the trans is at the ragged edge of capacity, even with the upgraded hardened input shaft, more clutches in every pack, better one-way sprag... The limiting factor for AODs is the inner input shaft (if you still want to have converter lock-up) of ~450lb/ft torque. The hardened inner shaft raises that to ~550lb/ft torque limitation. The one-piece input shaft raises it all the way to ~750lb/ft torque, at the cost of converter lockup.

 

Okay, but this is a truck.

Yah, 351 Panthers also had a rear sway bar.

 

Yes, but look at his post from the perspective of the original poster. That's all good info to know, should he decide on a trans swap, that if that's the case, he doesn't need to swap in a E4OD. Sure sounds more than reasonable enough that it goes right along with what your saying; they hold up just fine when swapped. That's good confirmation that's the case.



89F150XLTLARIAT, the C6 only has 3 gears. 3 being direct drive 1:1 ratio. Very old school. To make matters worse, there's no clutch/lockup disc inside the converter, so that is also constantly slipping to a degree. This is why it sounds like its screaming at 55MPH+.
The only way to fix it, is to replace it with a more modern trans (one with an overdrive gear and a locking converter or of course a manual trans swap) and by the sounds of things, these guys are claiming the AOD trans swap is probably the most affordable method and more than strong enough to hold up in an F150.

AOD = All mechanically controlled. 0.67:1 overdrive and locking converter. Taller OD gear than the E4OD for max fuel economy. Budget friendly trans.

E4OD = Electronically controlled. 0.71:1 overdrive and locking converter. Stronger. Strong enough to put behind big blocks and diesels but not such a high OD ratio, that you can't tow heavy loads with F250-F450 trucks while keeping it in OD. More expensive trans. Would require wire harness from 89+ E40D truck and PCM or aftermarket controller.

Manual trans options are more complex in your case, as you've already got a auto trans truck and it's best to have a donor truck for such a conversion, but those are M5OD and ZF5 options.
The M5OD (small block truck 0.81:1 OD ratio) is to the AOD as the ZF5 ( 0.71:1 OD in gas trucks) is to the E4OD.

There may be (and likely are) kits that allow the small block Fords to mate up to even more modern trans options, and if the truck is worth it to you, you could update it far past these trans options, making all these options look nearly as obsolete as these trans options do compared to your current C6, with options like double OD and tow/haul modes, and capable are far more power, but then you have more expense of the kit and the more modern trans and in most cases, will probably be worth more or as much as an 8th or 9th gen truck.......but it would be so worth it, for a super clean, rust free, mint or restored truck that a guy wanted to keep for decades.

Based on your current trans and how strong enough the guys are claiming the AOD is, that's likely your #1 pick. It would be mine.




The C6 was an absolute beast. A legend of legends among auto transmissions. It will forever remain a staple for hot rods and classics cars and trucks that get driven from time to time for enjoyment of the ride. But it's use as a daily driver trans option has long since gone. It's simply far too outdated for today's fuel prices and modern interstate speeds. Just like the mighty Ford 9", the long lasting 300-6 and the stump pulling power of the 429/460, the C6 it will go down in history as one of Ford best achievements.

 

Again, we have no clue what trans is actually in it nor do we know the OPs engine...he also mentioned OD. So your conjecture is absolutely pointless.

 

I have a feeling he'll tell us. Until then, we can talk trucks and help others anyway, just for the fun of it.


Did 1989 F150 trucks with any other trans, other than the C6 have: "My Gear selector says P,R,N,D,2,1" ?

Google AI claims yes with the E4OD:

• AOD (Automatic Overdrive): These 4-speed automatic transmissions featured an O/D. The gear indicator display on the dash read P, R, N, (D), 2, 1. The "D" with a circle around it indicated the overdrive gear.
• E4OD (Electronically Controlled Overdrive): Introduced in later years but occasionally seen in 1989, these models had an O/D indicator light and an "O/D Off" cancel switch.
• C6 (Heavy-Duty 3-Speed): Many 1989 work trucks came equipped with the C6, which was a 3-speed transmission and did not have overdrive. On these models, the gear indicator on the dash just read P, R, N, D, 2, 1 (the standard "D" lacked a circle).

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I skipped the 8th gen trucks. I had a couple 7th gens, skipped to the 9th. I never cared for the styling. So I'm personally unfamiliar, even though I've driven/ridden in a few of them many years back, not enough memory of them.


Yes, it's all speculation of course, until he tells us what the truck came with, what it has currently and what he means by "but the engine seems like it wants to shift into OD after in D"

Does that mean it used to go into OD? Does that mean he just got the truck and he's been so used to modern trans, that he's just expecting it to shift again? hahaha. That's right, we don't know yet.


I dunno if it's ever pointless to talk about a good old Ford truck while waiting for more details though.
There's a lot more readers interested in 'em than just the op too, I figure. I know good info is such a nice find when I'm searching the web and stumble upon such stuff, so I just share for the fun. It can help a guy down the road. I wouldn't bother of course if it was in a place where only the OP would go looking. All that is written because it will come up in a search for many. The more I'm using the new Google AI (that's advancing FAST!!!.... I only trust it so much, but it's getting smarter! Man, it's been a great help lately with my chainsaws, bars, sprockets parts, conversions, mods, etc. I'm going to dig to verify, but dang, it's getting good! Helping to know where to start searching and what for, saving me loads of time) I see it's pulling info from forums like these too, so it helps that knowledge base as well.