Slant six to 318

SlantSixSullivan

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Hey everyone, I know this thread is quite old now but I figured I'd bring you all up to speed on the project. Unfortunately, I suffered a job loss, which set me back a bit but everything worked out for the best (better job now). Anyway, without sharing too much personal information, suffice it to say I haven't gotten too much further than when I originally posted this.

Here's the deal - I have a complete 360, rebuilt by Jasper. The block is dated 1985, but it came from a firetruck which had 12,000 miles. There is no way of knowing how many miles the engine has since its rebuild, but I'm guessing fewer than 12,000. The engine is complete, ready to go in the car.

I bought a parts car for all the little spare goodies, like throttle cable, linkages, radiator, V8 K frame (I'll be using Schumacher mounts for now, but if I need them for a future project I will swap K frames then).

According to the fender tag on my parts car (89 Fifth Avenue) I now have an A998 transmission, which features 4 direct clutch plates. This is one more than 904s have, and one less than 999s have. To my knowledge, Chrysler only used A999 transmissions behind 360 engines. I do not think the A998 behind my 360 will be a problem, as I've done most of my low gear burnouts and neutral drops as a teenager and have gotten most of that out of the way.

I also scored an 8 1/4 rear from the Fifth, which saves me the time and work of modifying an 8 3/4 B body axle to work. Plus, finding the rest of the parts for it. The rear gear ratio is either 2.24 or 2.45. Hoping for the latter, expecting the former. Either way, the low first gear of the A998 will help with those ridiculous ratios until I can upgrade to at least a 2.76.

Finally, I'll be using the stock 318 converter with a B&M flexplate for balancing. I will see how pleased I am with the factory converter for now, but may contact CRT to rebuild mine in the future.

This is not intended to be a drag car. My goal is a respectable daily driver with just enough torque to put a smile on my face.

I just wanted to keep you updated, so you know your time and advice hasn't been wasted. I really do appreciate the help from everyone. Wishing you all a prosperous new year. Cheers
 
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Duke5A

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Are you absolutely certain you have an 8.25"? I have never seen a factory 5A with nothing other than a 7.25". That 360 probably has a very mild RV type cam in it, so you should be just fine with a factory converter. Think about using the /6 converter though as it will be a slightly higher stall than the V8 unit. As long as their both lockup or non-lockup they'll interchange. Might need to knock a welded weight off of it to make it neutral balance, that's it.
 

SlantSixSullivan

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Are you absolutely certain you have an 8.25"? I have never seen a factory 5A with nothing other than a 7.25". That 360 probably has a very mild RV type cam in it, so you should be just fine with a factory converter. Think about using the /6 converter though as it will be a slightly higher stall than the V8 unit. As long as their both lockup or non-lockup they'll interchange. Might need to knock a welded weight off of it to make it neutral balance, that's it.

3" axle tubes with an 8.25 looking cover. Does not look like any 7.25 I've ever seen
Have yet to take the cover off. Slant six converter is gone. Balance will be no issue with B&M flexplate
 

Duke5A

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3" axle tubes with an 8.25 looking cover. Does not look like any 7.25 I've ever seen
Have yet to take the cover off. Slant six converter is gone. Balance will be no issue with B&M flexplate

Can you post a photo of the axle? I can't be certain, but I remember their being something goofy where the 7.25" used to have 2.5" tubes and then went to 3" later on, or was that the 8.25? Someone will chime in that knows better. The thing I can say for certainty though is an 8.25" in a 5A that wasn't installed after it left the factory would be pretty damn rare.
 

SlantSixSullivan

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Can you post a photo of the axle? I can't be certain, but I remember their being something goofy where the 7.25" used to have 2.5" tubes and then went to 3" later on, or was that the 8.25? Someone will chime in that knows better. The thing I can say for certainty though is an 8.25" in a 5A that wasn't installed after it left the factory would be pretty damn rare.

I can put up a picture later, maybe not today. I heard, now this is purely anecdotal, that Chrysler dropped the 7.25 in the late 80s and some 8.25 axles made it into cars that would otherwise have had a 7.25. Out with the old, in with the new sorta thing. The car is an 89, after all, and if that's true, it very well could be the 8.25. Like I said, I've seen my fair share of 7.25s and this does not look like one (to me).
 

Camtron

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My 89 Fifth Ave came with a 7.25” rear end with 3” axle tubes that had a taper into the differential housing and flat sides on the diff cover. 8.25” will have straight 3” tubes into the differential with no taper and an oval diff cover.
A lot of guy have been fooled before and thought they had a 8.25” when they only had a 7.25”.
 

SlantSixSullivan

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My 89 Fifth Ave came with a 7.25” rear end with 3” axle tubes that had a taper into the differential housing and flat sides on the diff cover. 8.25” will have straight 3” tubes into the differential with no taper and an oval diff cover.
A lot of guy have been fooled before and thought they had a 8.25” when they only had a 7.25”.

I've done the homework on the differences and that is a common scenario I've read about. It indeed has an oval cover, with full length 3" tubes. If I pop it open to find it's a 7.25, I'll be very surprised. The 7.25 has more of an octagon shape, mine does not.
 

Mikes5thAve

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I've seen at least one 88/89 with 8 1/4 but very rare. A lot of people mistake the 80s 7 1/4 as one because of the 3" tubes and roundish cover compared to the older ones. But tubes 3" from end to end mean its 8 1/4.

The transmission is hit or miss. When it comes to 904s behind 360s I run them till they die and then go 727 and that's what I'd do in your situation also since you've already got all the parts now. Other then whatever linkage you need for the carb you're using. If it doesn't last then you can decide what you want to do with it.
 

SlantSixSullivan

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Here's a few pictures I got this morning. I can't quite make out all the numbers that are cast into the center section. Definitely 10?2? and below that, looks like 4364213. As for the date of manufacture, looks like the four digits are 8?21. The second number there could be a 3, 5, or 8. Hard to tell.

Definitely 3" tubes all the way and an oval cover.

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LSM360

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That's a rarity for sure. Wonder if it was swapped in.

Pretty sure A999 did come behind something other than 360's. 318 AHB's got A999 trans.
 

Camtron

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Yea, while my civilian 89 5th Ave came with the A999 with its 318, it definitely only came with a 7.25” rear end. Had to swap in my 8.25”.

Nice piece to have for sure.
 

SlantSixSullivan

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That's a rarity for sure. Wonder if it was swapped in.

Pretty sure A999 did come behind something other than 360's. 318 AHB's got A999 trans.

From what I understand, Chrysler never had too much rhyme or reason when it came to rear ends. Some automatic slant six darts came with 8 1/4s while 318 cars came with 7.25s. Who's to say the assembly workers followed the build sheet perfectly? Just happy with what I've got. I will be popping the cover off to change the fluid, and a quick inspection while I'm at it.
 

Kramer79

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Now I may have to check under the wagon, when changing the gas tank I swear it was oval...
 

Mikes5thAve

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Wagons usually had 8 1/4. And all aha and ahb cars. The rest depend on how the car was ordered. They use different driveshaft and because of the different gearing they need different speedometer gear so you're not going to have line workers randomly install an 8 1/4 for no reason.
 

LSM360

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From what I understand, Chrysler never had too much rhyme or reason when it came to rear ends. Some automatic slant six darts came with 8 1/4s while 318 cars came with 7.25s. Who's to say the assembly workers followed the build sheet perfectly? Just happy with what I've got. I will be popping the cover off to change the fluid, and a quick inspection while I'm at it.
Yes, you really are fortunate to have the 8.25! A lot of parts available for it like sure-grip and different ratios, and who wants to spend money on a 7.25?
 

SlantSixSullivan

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Just got around to popping that cover off the diff. 47 teeth on the ring gear and 21 on the pinion, so I've got the fuel sipping 2.2 instead of the highly sought after, tire shredding 2.45 like I'd hoped for (sarcasm). I can't complain, though, because the gears all look good. The oil I drained appears to be brand spankin'. There's no mentionable backlash in the pinion. I was going to pull the axles and inspect them, but I'll leave well enough alone for now.

Question: what can be said about the paint marks on the ring and pinion? Looks like 31 and 01. Is this a factory thing, or a sign of a rebuilt differential?

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Mikes5thAve

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I don't think I've seen numbers like that on any of mine. It's not very likely that it's been rebuilt being behind a 318 in a 5th Avenue. I'd almost wonder if maybe it was a replacement rear if the original 7 1/4 got chewed up at some point but the most common 8 1/4 to find for that would have been in the 2.45 2.7 2.9 type range out of an AHB.
 

SlantSixSullivan

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I don't think I've seen numbers like that on any of mine. It's not very likely that it's been rebuilt being behind a 318 in a 5th Avenue. I'd almost wonder if maybe it was a replacement rear if the original 7 1/4 got chewed up at some point but the most common 8 1/4 to find for that would have been in the 2.45 2.7 2.9 type range out of an AHB.

Thanks, Mike. I did think the paint was a bit odd at first. The fender tag indicates an A998 trans, but I still can't say for sure what rear end was supposed to be in it originally. According to the previous owner (for what that's worth) there have been no major mechanical issues to speak of. Like I said; for what it's worth
 
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