Hot Rods AD_NAPCO's 39 GMC Rocket 324 Build

I don't see any PO grinding mods to the shaft. What I see so far, is a single tooth cut on the spiral teeth for 1/R sliding gear. I believe that is cut like that to be able to get under the thin snap ring that has almost no end gaps...or it might be where the milling operation stopped, when cutting that trough? I'll look at one today.

Then I see the extended spline groove which is for the tang on the thrust washer for 2nd gear,

and the lengthwise oil trough under 2nd.

Did I miss something in the pics?

Olds tail seal number 1308163

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Walt, thanks! I'll be calling NW today.

Nope! I guess I just thought the grinding, both of the tooth and that trough looked too squirrelly to be factory. Glad to know it's meant to be like that. Thanks for that seal number!

 

Walt: Tail housing casting number is 1343940-2, overall length is 8 5/16" Front face of casting to center of speedo gear is 3/4"

Calling NW Trans now.

 

Check to see if these seal diameters work for you. Seals came from harwall and the rubber coating on the od allows for some compliance and range of diameters

 

Here are pics of the mystery hidden "snap ring" that is under the real snap ring that holds second gear on.

I did not show the "normal" main snap ring.

One pic shows how it sits in the bottom of the ring groove (look closely). On that pic, I installed the second gear thrust washer that has the locating tang on the ID. I was wanting to see if it could be installed with the tang 180 off, which might block oil to that long oil groove in the mainshaft surface. Lucky "us" as that oil groove is a bit too shallow to let the tang fit there. That is good news in case we thought we put it in the wrong spot, as this is mostly hidden with 2nd gear installed. The tang only fits that one partially elongated spline.

Back to that hidden ring. It measures .034" (a used one). It is most likely stainless steel, not tempered. It will hold second gear on if the thrust washer is installed, as the tang won't pass over it. (as long as the ring gap is not lined up with the tang)

I just can't figure out what the whole point of this ring is. I thought maybe it keeps 2nd gear on, during a trip down the transmission assembly line at the factory, but that makes no sense, as the real snap ring would do the same thing. If GM had the groove cut too deep for a standard snap ring, why would they not change the design;... so that's not the answer either.

Any ideas?? I just don't get it, but I sometimes miss the elephant in the room.

 

I checked and these dimensions will definitely work. Thanks for checking on that for me! BTW, how do you like driving your car with this trans? I have not gotten a chance to go through your build thread yet but I will be sure to check it out.

I have no idea either, Frank, but to be completely honest, as my dad would say, I'm as "green as a gourd" when it comes to transmissions. I'm learning a lot just going through this process, with help from you guys. I know I didn't see a ring like that in this box, but after everything I've run into so far that doesn't surprise me.

I was able to skim the HRM article that somewhat details this conversion and I did pick up the answer to the earlier question regarding the TOB retainer bolts that are cut off in mine. Remember how I mentioned that I saw a pic you had posted that did not have those bolt holes? I know why now. The HRM article says that only early 37 cases have the studs to retain the TOB retainer. Your case must have been late 37.

Brown truck showed up today with my new welder. So as soon as this trans is all back together again I'll be doing the mod on my crossmember. I also picked up a 39-46 Chevy truck 3 speed trans cheap on ebay. Going to go pick that up tomorrow as the seller is only a couple hours drive from here. I want to use stock pedals in my truck. I think it might help to have that trans to bolt the pedals onto to help with figuring out bracket fab. The pedals/master cylinder combo bracket originally are bolted both to the bell housing as well as the side of the trans. Also going to harvest the shifter from this trans and most likely graft it to my Buick stick. I know this is very un-hotrodder of me but I want this truck to be a sleeper of sorts. I want it to look mostly stock inside and out. Honestly I won't have enough gears out back to take people off the line anyway. I picked up a rear end from a 54 Olds with I think 3.24 gears... Long distance with no OD friendly gears. For the most part that's the way the truck was when I found it anyway... I mean it did have short gears in it, which were blown to smithereens along with the hydra-matic, but there were no real mods to the body and nothing 'hotrod' or 'custom' about the interior. I want the realization that something is different to be achieved from the sound, and a look under the hood.

Anyway, I left a message for John at NW Transmissions. Was supposed to get a call back. Didn't happen today. Maybe he'll call tomorrow.

 

Check out some of the last posts in my Build thread. Yesterday I posted a short ride along video. I only have about 100 miles on the car, and it it shifting and working better and better every time I take it out. Other than some clutch adjustment I did suck some grease ( a few oz ) out of the tranny. It was cold when I filled it, and I probably put the plug in before it was done dripping. Now that its dropped down its stopped pushing a little out.
I love the sound, in first gear it really sings, second is more of a growl......
I have a taller tires and a 3:78 rear. Kinda wish I had the 4:11's as it is a tough getting out of the hole.

 

Josh, John is not good at returning calls but once you get him on line he is a treasure trove of info. Be sure to ask him about the small ring that Frank put a pic up on. I keep forgetting to ask him. Check with him on the clearances of the cluster gear also. He had told me last week 12-25 but that was on a 37 Lasalle. Would think it would hold true for most, best to check. They have all the new thrust washers also. I will look at those tail housings today.

 

I was reluctant to do a long reply here on Josh's thread, but he did ask how these transmissions behave
I've watched your videos, and I instantly saw that your 32 behaves so differently than my 32 with the Buick based trans. Especially the video that your Dad commented on how first gear was "geared up". I assumed then, that you were running a 2.50 to 2.70 rear!

My car is 324 Olds, .030 over, 2x2 Roch AA backdrafts non-progressive, mildish hyd cam, 3.23 Olds rear, tall 760-15... and... my car will take off easily on flat ground at idle without touching the gas pedal. I did have a 3.42 and really did not notice much in first gear when I installed the 3.23...just a slight change.

Mine does not sound like your trans at all. Mine has just a bit of "straigher cut gear" noise in first, very quiet in 2nd. and, I'm baffled about your multiple comments on clutch adjustments on your thread. My clutch is mint, never changes. (I cut my own flywheel surface on my drum lathe, and cut my pressure plate on my bench lathe)

Now that I know your axle ratio, I have to believe there is a ratio difference in the older Buick gears. I say that for two reasons; one is my first impression of the first video; the second is my experiences with a few 34 LaSalles I work on. (similar trans design) These are close to 3900 pounds, they were 4.78 ratio. But one had a 1954 Olds rear with 3.08 gear. That car was such a stone around my lot.... awful! It had a first/2nd gear growl if you quickly throttled-up after it started moving. I assumed the gear faces were worn very badly. It also had a slipping clutch when I drove up the trailer ramps. Long story shorter, I put a 1934 LaS 4.78 rear back in, and the growl was gone and the clutch did not slip on the trailer.

Other possibility; Your Nailhead requires a shorter input gear shaft than the Olds shaft that most of us have, and your input is definately a stock 37 Buick. I have wondered how they did that with a newer Olds mainshaft. I know there are different syncros, some with non matching size blocker ring diameters for 2nd and 3rd. Many are symetrical like the later Olds. This means when you swap an input with a different blocker dia, then you are forced to find a 2nd gear that mates to the opposite blocker ring size. And then, 2nd must mate to whatever cluster gear teeth for 2nd. Gets worse when you try to use some 1/R sliding gears; some have a straighter angle on the teeth(more gear noise), which means you must match the cluster again. AND, those 1/r sliders; some have a tighter internal spiral teeth where it slides on the mainshaft!

My point is, that I don't know how much of yours is "37 parts", and therefor I don't know what ratio you have in each gear, compared to a full set of Olds Selector trans gears..

So, one thing I regret not doing with a bone stock 36-38 Buick trans, is writing down each gear ratio; 1-2-3 and reverse. I do not have any stock buick gears or transmissions here. I might be doing one for a hamber with Pontiac gears/tail parts, so I will do it then.

 

Josh, I do have that tail housing. Same number but with a different suffix. Probably some modest change they made in it back in the day. If you want it send me a ship to and you can have it. To save you further aggravation I will blast it in my "big cabinet with my big compressor" and will etch it for you. All I ask is that you take care of the postage........

 

Just two minor adjustments on the clutch. First time I had the free travel a Little tight and second time I overshot a little and had too much.
You are probably right on the gearing difference.
I also improved drivability with a stiffer throttle return, and just in general getting the feel of the car. Like I said everything is working better and tonight I should get another 80 miles on the car.

 

Walt... That is so cool. Thanks so much! I will PM you my info.

I just got back from picking up that 39-46 Chevy truck 3 speed trans... I now completely understand why some of the old timers call it the "peanut" trans. This thing is tiny! I'm amazed that these little turds held up as well as they did in trucks. The 37 Buick trans seems so much more stout... And the 34 and 36 Olds transmissions that were on the seller's bench were much the same. They were the 5 bolt tops and were still much bigger. One thing I was amazed at was that the 36 Olds trans according to the seller, who is in his early 70's, is synchro'd in all three gears, where as his 34 Olds trans is not. The cases look identical.

Frank, that makes me feel better about my engine/gearing choice. My 324 is .060 over, mild cam and will be running the 4x2 Stromberg 4A's with the 3.23 gears. I'm guessing my wheels/tires will be a bit taller. I think I'll be running either 6.50 or 7.50-18's... Either way it shouldn't make much difference.

 

Well, I just spent a while reading back through this entire thread to refresh my memory as to what a long strange trip this has been. In the process, I looked through the pictures I took the day the Buick/Olds trans parts arrived. Turns out I did not actually pull the bonehead move I thought I did. The crossmember I have here IS the one that came with this setup, and the one I got rid of is the one that was under the Hydra-Matic. So my thought is now that the motor mounts are actually what is different... The odd thing about that is that just to double check, I looked at Fusick's site and the mounts I bought are what they sell for manual trans cars... So I don't know what the heck to think. Either way I will be modding the cross he sent me.

 

Josh, found a set off no name covers. Had them up in the attic over the garage. Don't go up there much and kinda forgot about them. Did you find a set yet? I think these may be off of a 371 ??? lost track of all this stuff....they are painted gold if that is a hint.

 

Cool... I think the gold covers may well be 371's. Can you compare them with the 324 covers you have for dimensions? I'm curious how much difference, if any, there really is.

 

Should be about a 1/4" longer

 

Cool. So centered up on a 324 head/gasket, that 1/8" on either end shouldn't be too big a deal? Paul have you ever run across any of the 324 no-name valve covers from the GMC trucks?

55 and 56 GMC 550 and larger trucks used the 324, and in 57, they used the '370' (371), and I know that the 324's were no-name covers as well on the trucks. These images are from one of the GMC Master Parts Books I have.

 

No experience with the truck engines, and all my smooth covers came off of 371s.

 

I've been looking into the Olds transmission tailhousings. I found an odd one that came from a very old modded Buick topshift that has all Olds internals; it came out of New Jersey with no known history...

This housing is 1/4" longer, not counting differences in seal protuding beyond the tail. It is night/day difference in the cast material to support the rear bearing...

Went into the 1958 parts book for housings; here are the 88/S88 choices:
1951 is same for 88,S88,98
51-53 is same for 88,S88
54-56 is same number as 51-53 88,S88
Here is the shocker to me; 54-56 88,S88 is different yet, for: Police, Taxi,Fleet !
57-58 is another different number, but could be due to the new bolt-on yoke or a shaft OD change?

So I looked up the mainshafts to see if 54-56 Police/Taxi was different than 54-56 standard duty. It is same for ALL 54-56.

I'll try to get pics today of the two housings.,

I have a known 1953 housing, and it looks like the common one. So, either the odd one is very early "casting"production on 51/52, or perhaps might be the Police/Taxi? They have completely different casting numbers, not just the suffix codes

on another thought; I was wondering why these crack. If you look at the gear teeth angles, second gear is most likely the suspect on when the most rearward thrust is on that rear bearing? Third gear gives no thust IMO. And first/reverse slider is far less tooth angle, and besides that, the thrust would be trying to move the slider on the spiral splines, rather than loading the rear bearing. If this is true, would that explain the heavy duty housing for Police/Taxi?? Seems economically silly to me, that GM would not just build ONE good H/D housing, rather than designing two housings?

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Correction to make on part numbers I just posted today;

The 88/S88 Police/Taxi is the same part number as 1952-1955 98. (98 is supposed to be longer). So, that means the Police one is longer than a regular housing, right? But I don't know how much longer the 98 mainshaft was? It can't be just 1/4" longer, so if that is true, what is my 1/4" longer housing?

Pics show the silver colored housing, modified for Buick with elongated holes. I tried to show a view so you can see the bearing support part of the casting is close to 1/4" thick. That would be the deeper step. The regular ones vary from a bit over 1/16" to just under 1/8".

The silver one might look broken in one spot on the bearing support area, but that is the same casting void that was made to clear the speedo drive gear ass'y. The other housing also has that void, and that seems to be where the weaker ones start the cracking.

The inner "core" casting is different. There is a small raised rectangular cast area, and the silver one has the extra meat going inwards more by looking where that block ends. So, it is different cores, not just a casting shift.

 

That silver one certainly looks much more stout... Frank, have you identified how many years the selector transmisions are potentially donors? I have a call into a wrecking yard that thinks they may have a good donor trans. I only knew 51-56, but if I can give them more years, say into the 60's, that might be helpful. As long as the tailshaft will mesh, I could use the longer parts, as I don't have a set driveline length yet.

 

Standard trans were rare past 55-56.. I have heard that from many older Olds race guys. So, chances of finding a newer one, go down, rather than up. Also..., I have been glancing at a few 57-58 parts in the book. There was the new bolt-on rear yoke in 57, but there must be a huge change inside; because the rear housing, rear bearing, mainshaft, speedo drive gear, etc etc, all show a new number in 57. I would not chance buying a post-1956 part, unless you can match it in person, but the book says it's different, so why chance anything?

I took the only "mainshaft measurement" listed in the 58 book; that was 23-3/4" long for a 52-55 98..then measured a random Olds one I had handy, at 19-7/8" approx.

So, my 1/4" longer housing is for the shorter trans. But what is it from?

The silver housing casting number is 1165430-1
The common ones are 1343949-3 (and I have other single digit suffix ones here, like -4)

I'd wait it out. Run yours for now. The snap ring should hold up under normal driving, and it is a quick part to swap later, if you find a mint one. JMO


BTW, I see some references to "shielded type" when I glanced at the rear bearing lists.

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Yeah, just in case, I just went out and cut the cracked portioned out of my housing and smoothed everything with a carbide deburring bit in the dremel. I think I may have 1/3 of the original surface left. I have a couple leads on possible transmissions. Waiting for one yard to call me back, and another based on a craigslist ad only about 1.5 hours drive from here. So we'll see! If I don't get any solid affirmatives, I'm going to put it all back together once the rebuild parts get here from Northwest Transmissions anyway. Thanks again, Frank and Walt!





I still need to wash all the metal filings out.

 

Ok Rocket guru's, .. here is a copy/paste of a PM I rec'd yesterday from a guy here that has never posted.. He was asking about some 57 stick parts, and this was added in the message:

"""Back in the day I had a 57 - 88 convertible that I converted to a standard transmission. I lived in Santa Ana, CA at the time and there was a transmission shop on Harbor Blvd. that used a 38 Buick box with an old time floor shift and put an Olds tail shaft on it to fit the car. I must have found the standard parts in a local wrecking yard. (wow) It still had the automatic rear end in it so the gears were mighty tall. Any way it was slow off the line but it would do 65 in low gear. Never did try to find out what top end speed was."""

he also said he sold the Olds for a near new 61 Cad conv, but always wanted another 57 Olds conv....and now he has finally found another 57 conv and is trying to do a factory type standard.

Seems like people that had Olds back then, want to relive it... A couple of years ago, the brother of John Delorean called me about some stick parts for a 56 Olds 2dr Htp that he was cloning to be the same as what he had hotrodded in Detroit in the 50s.. he's over 80 years old and still at it

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Frank, fwiw I have a nos 98 shaft in stock. I also have what appears to be '57 tranny with the bolt on yoke that is in awesome shape. I plan on gutting it and installing the gut in the 37 Buick box so we will have first hand knowledge on this application.
Further, fwiw, NW tranny has a book with all the tail and case numbers and can id any unit as to year and application. One of my selectors (the rusty one from that bad CT deal with the 371) actually turned out to be a 56 Pontiac unit.
Josh, if you get to the point where you find a 98 longer tail housing in good shape you can have the 98 shaft and use your other parts on it. I scooped that item off Ebay years ago for $50 + the ride! Something to keep in mind to open up other opportunities.

 

I'd be wary on that swap, as there are so many changes showing up in 57 parts book. I'd take the tail housing off to check the OD of the rear bearing first.

The bearing is new for 57 but it could be the ID, rather than OD, but the tail housing AND mainshaft changed in 57 also. Perhaps the tailshaft is bigger OD, so maybe the tail housing was enlarged for the internal bushing bore?

I'd be looking and measuring all the pieces, as you don't really want to bore the 37 case for a bigger OD bearing...if it is bigger OD


EDIT:.....I just looked up the main trans case itself. The 51-56 is same number, but there is a new number in 1957...so, a betting person would assume the rear bearing bore is bigger..?

Walt, if you have a good Pontiac mainshaft, to go with the Pontiac tail housing, maybe a bit more parts book work would tell if "some" of the 1957 Olds internals might be usable?

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Thanks, Walt! I appreciate that. I will definitely keep my options open. My rebuild parts are supposed to leave Ohio today. The CL ad in Marysville struck out. He said he had several selectors a few years ago but they are all gone now. Has multiple 303-324-371 motors though. If I had more disposable cash at the moment I'd be heading over there. I'll be keeping his number on hand though. I was thinking that I read somewhere that the thermostat housings for 371's were aluminum? I'd like to run an aluminum thermostat housing on my aluminum intake... Might help with the electrolysis issue? Still waiting on a call back from the wrecking yard.

 

I used a '58 selector as donor for my '37 Roadmaster case, went together just as F&J described.

371 (early) thermostat housing is aluminum, but has different bolt spacing than earlier housings and will be susceptible to the same electrolysis as any other aluminum in your system

 

I'm obsessed with there old transmissions for some reason...I wish I could have seen all the pieces to compare with 51-56...I'm wondering about all the many part number changes...

One question I did want to ask; is can a 51-56 slip yoke be used instead of the bolt-on?...without changing anything else?

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Thanks Paul. I will keep my options open then. If I can get a complete donor trans from a later car at a reasonable price I will definitely grab it.

I also will not worry about that thermostat housing!