mchartier105
Well-Known Member
It can be done, but you have to cut the bellhousing off...it would have been nice if Mopar had a big block OD.
JW Performance 92457: Ultra-Bell Bellhousing Big Block Chrysler to TF-727 | JEGS
It can be done, but you have to cut the bellhousing off...it would have been nice if Mopar had a big block OD.
Fixed to say:A500s are 2.74-1.54-1.00, same as A999s and some A998s
A518s are 2.45-1.45-1.00, same as A727s, A999s ,and some A998s
it would have been nice if Mopar had a big block OD.
I had thought about doing this, more than a few times.It can be done, but you have to cut the bellhousing off...
JW Performance 92457: Ultra-Bell Bellhousing Big Block Chrysler to TF-727 | JEGS
JustWondering,
In 1987 (or 1988), Chrysler came out with an overdrive automatic transmission, for pickups, vans and Jeeps.
Basically what Chrysler did, was they added the overdrive onto the tail section of transmission.
The transmission you have in your 5th Ave looks like the first one below, and is called A999 (which is mostly the same as A904, A998, or newer versions of same transmission is called 30RH, 31RH, 32RH).
The newer versions, the first digit is the number of speeds (3), second digit is the strength (0, 1, 2 ~ 9), third digit is which direction in vehicle (in this case North to South) and forth digit is Hydraulic vs Electronic (n this case Hydraulic).
View attachment 28195
The four speed version is called A500 (or newer versions are called 40RH, 42RH, 40RE, 42RE & 44RE) and looks like this:
View attachment 28196
The red arrow is where the overdrive is located at. The blue arrow is where the different transmission mount attaches.
The heavy duty transmissions called A727 (or 36RH or 37RH) for 3-speed, or 4-speed version is called A518 (or A618, 46RH, 46RE, 47RH or 47RE), and looks like:
View attachment 28197
The A518 is top, 727 is bottom.
There is a guide that describes this a bit better at our forums sister site http://www.forbbodiesonly.com/moparforum/threads/your-guide-to-the-727-904-transmission.17287/
View attachment 28198
This chart was taken from that site and modified a bit. The distance from engine to case/tailhousing flange (red line) is the same on all A904, A998, A999, A727, A500 and A518’s.
The same also applies to engine to transmission mount on A904, A998, A999 and A727 – but is different on 4-speeds (A500 and A518).
Our cars never did come with overdrive (or with fuel injection) but should have. It would make a lot of modifications a lot easier, if they did.
On pickups and vans, it is very easy to change one over from 3-speed automatic to a 4-speed automatic, and either change the transmission mount and/or the crossmember.
“I have been told” (but no first-hand experience on this) the tailhousing section of the overdrive transmissions (where the overdrive is located at or red arrow in above picture) is too large in diameter to fit in the floor pan transmission tunnel section – without modifications to floor pan first.
I hadn’t tried this modification yet, so have no first hand knowledge about it.
I know the transmission crossmember has to be modified for the overdrive transmission to fit (which pictures in above posts show that).
I don’t seen any notes in this thread about modifying the floorpan or the upper part of transmission crossmember (welded to frame) – but it appears the upper crossmember might have been trimmed or cut to allow for the larger diameter tailhousing to fit, possibly (but could be mistaken).
View attachment 28199
This area is not a high stress area, like the older Chryslers are – so some trimming of parts shouldn’t matter a lot. That said, if trimming/cutting is required – it would be nice to mention that in the post – for other members here who is thinking about doing the same thing.
I like overdrives – especially ones that are a direct bolt in. That way you have a decent differential gear (for take-off power) as well as decent (better?) fuel mileage.
BudW
You got it.So you are saying that you have a DIY way to modify the frame and bracing so that the new/different transmission sits correctly under the car - somewhat offcenter - and somewhat longer than the original transmission
And
you want the new/different transmission so you can change the RPM to gear selection in order to optimize the highway cruise or the initial start up.
Optimizing the highway cruise means you can reduce the wear on the engine due to reducing the RPMs needed to push the car forward-- the different transmission and gearing lets you obtain that efficiency. Reducing the RPMS at cruise would also buy you a reduction in noise from the engine.
If all that is correct, then my last question is how does the new gear box get activated? Is there a separate lever to engage it or is there something inside the new transmission that activates it when needed?
Larger yes, somewhat off centre, not really. It's pretty straight inline with the motor and rear end and all that's correct, to answer your last question, I have it set to a toggle switch on my dash for OD and lockup, but I'll be moving to pressure switches to control it automatically once money permits.So you are saying that you have a DIY way to modify the frame and bracing so that the new/different transmission sits correctly under the car - somewhat offcenter - and somewhat longer than the original transmission
And
you want the new/different transmission so you can change the RPM to gear selection in order to optimize the highway cruise or the initial start up.
Optimizing the highway cruise means you can reduce the wear on the engine due to reducing the RPMs needed to push the car forward-- the different transmission and gearing lets you obtain that efficiency. Reducing the RPMS at cruise would also buy you a reduction in noise from the engine.
If all that is correct, then my last question is how does the new gear box get activated? Is there a separate lever to engage it or is there something inside the new transmission that activates it when needed?
The Chrysler 4-speed automatic transmissions are computer controlled (either a little or a lot).And because it is electric shift, our cars don't have the 'smarts' to be able to tell it to shift into overdrive?
I might be getting my hands on a few 5-speeds soon – and may have more information on them shortly.It woulda been nice if Mopar had made a SBM manual 5-speed with tight splits, and a drop-down od Fifth, as a direct fit to where the A833 had been.
My 5th Ave is so fast, that bugs land softly on the windshield then buzz off, instead of going “splat” - when driving.21.1 as fast as a stock 1971 Bug. lol