Transmission Fit Options

-
M

Mopar Virgin

Well-Known Member
Joined
Feb 27, 2022
Messages
102
Reaction score
36
Location
Trout Lake, WA
From what I understand, only a 904 or 727 will fit into a '68 Barracuda without tunnel modification. Anyone know or tried an A500?

My research indicates it's from the same family, but not clear on ability to bolt to a /6 or dimensional retro-fit. Objective is to get a better highway cruiser (e.g. lower RPMs) for longer distance drives with better MPG to car events and 100-mile weekend drives with friends (thx Brandon).
 
I’ve got an A500/42RH in my 65 Dart wagon that just finished constructing a transmission crossmember member for it. To get it in the car, had to modify and enlarge the upper crossmember support which necessitated tunnel and floor work. I understand the 67-76 is somewhat easier but still requires modifications. I’m sure there are some on-going threads on the 67-up.

you will require some kind of adapter to run any kind of OD behind a slant
 
There are many threads on this and there was JUST a big one the other day. Search it up. Guys posted "how to" links from previous posts.
 
65 Dartman said:
I’ve got an A500/42RH in my 65 Dart wagon that just finished constructing a transmission crossmember member for it. To get it in the car, had to modify and enlarge the upper crossmember support which necessitated tunnel and floor work. I understand the 67-76 is somewhat easier but still requires modifications. I’m sure there are some on-going threads on the 67-up.

you will require some kind of adapter to run any kind of OD behind a slant
Click to expand...

THIS
 
Trout Lake, between the elevation, rolling hills, and George wings an OD may not help the MPG department. What are you getting now and what is the rear gear ratio? Stock slant?
 
dano said:
Trout Lake, between the elevation, rolling hills, and George wings an OD may not help the MPG department. What are you getting now and what is the rear gear ratio? Stock slant?
Click to expand...

Haven't checked the rear gear ratio yet. Spend yesterday disassembling the front-end valances, but that very topic came up with my friend while doing the work. I'll get back to you that at some point. The OD isn't for the Trout Lake geography, rather, for longer drives on I-84, I-97 and OR Hwy 26. Also, the drive from Trout Lake down to civilization (i.e. Hood River & The Dalles) via WA SR-141 is a straight gentle 25-mile/1700ft drive to and from SR-14, so to go anywhere is a minimum 50+ mile round trip. Also, my experience with my '49 Chevy with a 3speed is that at 65mph I was pushing 3000RPM with the max gearing we had and the only non-fabrication option was to get a larger diameter tire, which dropped it to 2750RPMs (still a bit too high for mileage and ambient noise for this classic rock enthusiast to hear his music on road trips).
 
Mopar Virgin said:
Haven't checked the rear gear ratio yet. Spend yesterday disassembling the front-end valances, but that very topic came up with my friend while doing the work. I'll get back to you that at some point. The OD isn't for the Trout Lake geography, rather, for longer drives on I-84, I-97 and OR Hwy 26. Also, the drive from Trout Lake down to civilization (i.e. Hood River & The Dalles) via WA SR-141 is a straight gentle 25-mile/1700ft drive to and from SR-14, so to go anywhere is a minimum 50+ mile round trip. Also, my experience with my '49 Chevy with a 3speed is that at 65mph I was pushing 3000RPM with the max gearing we had and the only non-fabrication option was to get a larger diameter tire, which dropped it to 2750RPMs (still a bit too high for mileage and ambient noise for this classic rock enthusiast to hear his music on road trips).
Click to expand...

It's a drive from there to get anywhere. I grew up out side of The Dalles until the mid 90's, both my wife and I'd family are still there.

The only issue with the OD is it may drop the slant out of its power range. I've never owned or driven one so I don't know how a stock one would do at 70 on a flat at 2k RPMs or less. I'd see whats in it for a rear gears first, dropping a higher ratio in might be easier.
 
Compared to a stock trans in a 68 the gears are wider spaced in 1st thru 3rd. First gear seriously lower, second half that difference. This means you can use lower gears out back and still have some umph getting going, or keep the current gears and get a boost in first and second and still have 4th gear for the highway.
 
Just get a wide-ratio Loc-Up A998/A999, a 2400TC , and less rear gear, Cheaper by far and equally effective.
At the stock stall of about 1800; IF your torque was at 100 ftlbs, your power would be 35hp. With same 100ftlbs at 2800, your power would be 53hp, or about 50% more. So really, if you wanted to you could regear to 50% less than what you currently have and have exactly the same First-gear power delivery.... and 50% less rear gear would get you 50% less rpm on the hiway.....
But, with a wide-ratio A998/A999loc-up; you can pull another two tricks.
First is the Lock-up which is probably good for at least 5% less rpm @ hiway speed and Second is this;
Say your hiway rpm currently is 2700@65 with 27" tires, with the A904. That translates to 3.23 gears which would be typical for a 68 Barracuda. Ok so; your starter gear would be 3.23 x 2.45=7.91 And say your engine makes just 130ftlbs at 1800, which is your stall, which is 44hp.
So then; with your gas pedal floored you would be putting down; 44 x 7.91=352 hp into the rear axles.
Now, lets consider the Wide-ratio lock-up, 2.76 gears, and a 2400TC. For same Torque at 2400 now, the power is
130 x 2400/5250=59hp, and 59 x 2.76 rear gears x 2.74 low gear, is 449hp into the rear axles.
Now with 2.76s she will cruise 65=2230 in lock-up.
But don't miss that 449/352= plus 28% power going down at zero mph.
The A998/999 bolts right in, as does a 2.76 geared Complete rear end that people occasionally give away. Even the driveshaft still fits. You can be all swapped over in a few hours. If you keep the 3.23s then you will need a SureGrip, lol.
BTW;
I already did this swap in a car of mine, back in the 70s, but with a 2800TC. In a word; sweet.
 
AJ/FormS said:
Just get a wide-ratio Loc-Up A998/A999, a 2400TC , and less rear gear, Cheaper by far and equally effective.
At the stock stall of about 1800; IF your torque was at 100 ftlbs, your power would be 35hp. With same 100ftlbs at 2800, your power would be 53hp, or about 50% more. So really, if you wanted to you could regear to 50% less than what you currently have and have exactly the same First-gear power delivery.... and 50% less rear gear would get you 50% less rpm on the hiway.....
But, with a wide-ratio A998/A999loc-up; you can pull another two tricks.
First is the Lock-up which is probably good for at least 5% less rpm @ hiway speed and Second is this;
Say your hiway rpm currently is 2700@65 with 27" tires, with the A904. That translates to 3.23 gears which would be typical for a 68 Barracuda. Ok so; your starter gear would be 3.23 x 2.45=7.91 And say your engine makes just 130ftlbs at 1800, which is your stall, which is 44hp.
So then; with your gas pedal floored you would be putting down; 44 x 7.91=352 hp into the rear axles.
Now, lets consider the Wide-ratio lock-up, 2.76 gears, and a 2400TC. For same Torque at 2400 now, the power is
130 x 2400/5250=59hp, and 59 x 2.76 rear gears x 2.74 low gear, is 449hp into the rear axles.
Now with 2.76s she will cruise 65=2230 in lock-up.
But don't miss that 449/352= plus 28% power going down at zero mph.
The A998/999 bolts right in, as does a 2.76 geared Complete rear end that people occasionally give away. Even the driveshaft still fits. You can be all swapped over in a few hours. If you keep the 3.23s then you will need a SureGrip, lol.
BTW;
I already did this swap in a car of mine, back in the 70s, but with a 2800TC. In a word; sweet.
Click to expand...

First of all ... THANK YOU VERY MUCH for taking the time to share this ... I really don't know a think about this stuff, but my two good friends will understand it all and help me with my car illiteracy (e.g. Mopar Virgin) to make sense of what you've outlined. I may circle back on this in 1-2 weeks as we complete the dismantling of the body for the paint and body shop. After that I'm into engine dismantling for the machine shop and this will be come the full-time focus. Thanks again !!!
 
AJ/FormS said:
So you are staying with the slanty then?
Click to expand...

I am staying with the /6 ... Convinced it will be more of a conversation piece versus blending in amongst all the V8's everyone generally opt for. I did some reading on the A998/A999 and not clear what the heck the real difference is versus an A904, perhaps you could summarize in a sentence? Also, do they have the same bolt patterns, or would I need some type of converter?
 
All the A9xx series autos come in just two patterns; either SBM(Small Block Mopar) or slanty.
The A999 and some to most A998s are a wide-ratio trans with ratios of
2.74-1.54-1.00, compared to the standard A904 ratios of
2.45-1.45-1.00.
Some A998s have the standard ratios.
----------------------
IIRC; ALL A999s have a lock-up convertor, but NOT all A998s do.
The A998s are heavier duty than A904s, and A999s are heaviest of all.
You cannot mix parts from one, willy nilly, with parts from another; some parts have to be kept together.
-----------------------
The ratios do not look that much different until you work out the percentages. For example; 2.74 is 11.8% deeper than 2.45; which is the same as going from 2.76 to 3.09 rear gears., or from 3.23 to 3.61s.
As for Second gear; 1.54 is 6.2% greater than 1.45, which is the same as trading 3.23 rear gears for 3.43s
In other words, you engine will feel more powerful by the % differences before changing rear gears. So then,with the wide ratios, your 225 will feel like 252 in First gear, and like 239 in Second, then fall back to 225 in Direct-third.
The loc-up feature is worth about 3 to 5% rpm or 100/150 rpm at 65mph, so dropping your slipping3.23 that might rev like a manual trans with 3.33s to 3.40s, back to a true 3.23. The rpm-drop is worth about half the percentage , in mpgs. So say 2% or 1/2 mpg with 3.23s
None of this comes free because with the wider ratios, the engine rpm will drop lower for the same shift-rpm. This can be bad news if you chose a cam with a narrow powerband. For example; shifting at 4500, and using the A904, in First gear, the rpm will fall to 2655, whereas with a wide-ratio, the rpm will fall to 2529; a difference of 129rpm, usually no big deal . You can easily overcome this with more than stock stall. I really liked my 2800.
All in all, this is IMO, a very desirable improvement.
 
Last edited:
You must log in or register to reply here.
-

Back
Top