The Stovebolt Site Forums The Shop Area General Truck Talk What Frame is My Project Sitting On?

I purchased this truck thinking it was a 1940 KC 1/2 Ton. There were only 2 bolts holding the cab to the frame...and it turned out that the holes to mount the cab the correct distance from the radiator were missing!
Once I started looking at what I actually had, it seemed obvious that some things were not correct.
Eventually I measured the wheelbase and it measures 115". (It seems that the 1940 KC would have had a 113.5" wheelbase from what I have read.)
Measuring across the outside of the front of the frame shows 27".
Measuring across the outside of the rear of the frame shows 46 3/16".
The frame length measures 172 1/16"
Given all the above...I can't figure out what frame I have because nothing seems to match!
Also, in case it helps to confuse things further, all the drawings I have found (and attached to this post) show frames with 5 crossmembers...my frame does not have a crossmember between the one the rear of the engine sits on and the one that holds the parking brake cable pulleys.
The measurement across the rear of the frame (46 3/16") is close to a 1940 or a 1947, but the wheelbase being 115" is not correct for either of those years. (115" wheelbase matches what I find for a 1941, but the frame for that year shows a 44 1/4" measurement across the rear.)
The measurement across the front of the frame (27") doesn't match anything.
I wouldn't worry too much about this as it is obviously a Frankentruck, but as I move forward trying to make it roadworthy, it might be important to know what I am dealing with regarding steering components, etc.

Thoughts?

Nick
Having seen your truck and us pondering the mystery previously without solving the mystery so far, I’m wondering. Could the frame possibly not be from a Chevrolet? I think I recall us checking the possibilities it was from larger models, earlier and later year models for Chevy trucks and unless something was missed there was no joy. Maybe one of the other guys has access to other Specifications books?

Hey Sparky!

It had not occurred to me that the frames for GMC during this period might be different. There are so many things that seem correct - but others that don't match up!

Good question.

Nick - Just a note that I think this topic better fits in the General Truck Talk (GTT) forum so it's been moved there for further conversation and help.

When I get some time later today or tomorrow I'll dig through my GMC books to see if I can locate dimension details on similar year frames to see if there may be any correlation with your numbers and description.

In the meantime, maybe some folks with GMC info will chime in?

The info search might even need expansion to include ford and dodge?

I think you have a 1939 Fargo.

(Just kidding, but not outside the realm of possibility)

I would be surprised if the chassis is not GM because so many things seem correct...but I know that I don't know!

Is there a source for specs on GMC trucks similar to the OldCarManualsProject?

Maybe you're correct, Otto...maybe it is a Fargo!

Memory is foggy, but I wonder if REO trucks had some similarities too?

Nick - I got a chance to do some digging in the GMC resource books I have on hand. Below are snapshots of what I think may be relevant info to try and help you answer at least some of your frame questions.

The 1939-40 GMC Shop Manual, 1939-41 GMC Book of Parts and 1939-45 GMC Parts Books show 1939-40 1/2 ton Model AC-100 trucks had 113-1/2" wheel bases. I think that rules out your frame being a 1939-40 GMC, which matches with your findings on the same Chevy 1/2 tons.

The GMC 1939-41 and 1939-45 Parts Books both show 1941 and later 1/2 tons Model CC-100 have 115" wheel bases. Again same as your Chevrolet frame wheelbase dimension findings.

I think the primary difference between the two frames (Chevy vs GMC) is the GMC front engine/radiator cores support cross member is farther forward than the Chevy to support the longer GMC engine. I think that accounts for your difference in the different distance from the cab and radiator since the GMC radiator is meant to be farther away from the cab than the Chevy. The different (farther forward) GMC front engine mount location coupled with the rear engine cross member will mean your Chevy 6 and transmission package are going to fall short of the front engine mount location, which I think you had been discussing in another thread.

As to the missing cross member between the rear engine mount and parking brake cable pulleys mount, IIRC that cross member is for the rear of the transmission and I think it's a bolt in (removable) unit. It may have been removed by a PO and not reinstalled.

Unfortunately none of my GMC books actually give frame dimensions like the Chevy diagrams you've shown, so I can't confirm if there may be differences in the overall length or width between the Chevy & GMC or not.

Perhaps there are some more knowledgeable GMC guru's that have the frame dimension details, or a current truck owner(s) that could take some measurements and post to try and help clear up what you have???

Sorry I couldn't be more help in clearing up the muddy waters.

Nick
Can you post photos of the bumper brackets, both front and rear and especially the front frame horns? This might help narrow the possible options? Maybe someone will recognize something helpful.

Dan, I did wonder when I first received the project and started asking questions here on the forum, if any additional support was needed for the rear of the engine (a '54 Chev 235 set up for a Powerglide) with a 3 speed manual transmission attached. I was wondering because it had a ratchet strap stretched under the rear of the transmission. I removed the strap and the engine/trans seem happy sitting on the mounts seen in the first photo attached. Also, there are some empty holes (visible in the second photo) that MIGHT have been intended to hold that missing cross member. I am attaching a photo of the front portion of the frame that might help identifying if the front crossmember is further forward than what Chevy folks would expect. Dan, every question or observation probably brings us closer to an answer!

Sparky (Lee), I am attaching photos of both the front and rear ends of the frame and also some different general view of the frame. (I don't have any bumper brackets.)

I am heading out of town for a week (should have left an hour ago!) but I will take my photos and a laptop with me to carry on this discussion.

I sure appreciate all the input!

Nick - I took a look at your new pictures and went back and read through your old posts on the engine placement and cab/radiator support relationship. From appearances, your '54 235 and 3 speed are correctly fitting on the existing frames front and rear engine support cross members. Since the 235 is the same length as the original 216, and the spacing of the first two cross members properly fits the Chevy engine and transmission, I think we can probably safely say that you have a Chevy frame, albeit most likely a '41-'46 considering the 115" wheel base. The longer GMC 228 and 3 speed would not fit in your existing frame.

The 2nd of your new pictures shows the bolt holes in the frame that correspond to where the rear transmission support cross member is supposed to be. Reading in both 1940 and 1941 Chevy Shop Manuals, the cross members are noted as "front engine support", "rear engine support", "The second cross member is of box member construction for its entire width. Bolt attachment to the side rails provides easy removal for the servicing of the transmission.", the third cross member "...supports the hand brake cable pulleys..." and "A single rear cross member is used." That covers the "5" cross members that make up the frame for both years.

Below is a picture of the bolted in cross member and still mounted transmission bracket which bolts to the rear of the transmission at the lower torque tube ball collar bolts. Interestingly enough, according to the Master Parts Books, 1937-40 All Commercial trucks (exc. KF) and 1941-46 all Commercial 1/2 ton trucks all used the same transmission support cross member and support bracket. The picture came from this eBay ad. This one seems a bit on the pricey side, + about $70 shipping, but there looks to be others out there that may be better priced, so some searching may be in order.

I know this doesn't answer the width dimension inconsistencies from the 1941-46 Chevy truck frame specs, but perhaps that may not be relevant except when you mention the steering components. I think those are going to have to be discussed and investigated in a different thread in the Driveline forum.

Thanks, Dan.

It sure looks as though that crossmember (or one like it) would bolt into the frame I have. I would request the length to make sure that the width is correct to fit between the frame rails.

I agree that knowing what frame I have is not a requirement except for finding specific replacement parts for specific subsystems, but knowing what it is would make a difference (someday) when time comes to turn it over to a new owner.

Nick - Just one further note concerning identifying what you have. On the suspension and steering parts, ie; steering gear, axle beam, steering arms attached to the spindles and rear axle, the majority have casting numbers on them which can be used to help figure out what they are. Just food for thought as your project continues.

As you come across those details, post them so we can try and help ID things for you.

Thanks, Dan.

I am continuing to hope that someone may eventually have a suggestion about the frame that would help nail down what it actually is. But it may remain a mystery.

Nick
The pictures you posted showing the frame ends and frame horns appear to match those on my ‘46. So, my speculation about another manufacturer seems to be eliminated. In looking at the photos showing the rivets used to mount the cross members to the rails it looks like any custom work would seem to be eliminated as well. The rivets look to me like they are original.

Well, Sparky, that adds more weight to the concept that, perhaps, I should just continue to move forward with work toward making the truck roadworthy and not worry about details of chassis I have until I run into something that presents a problem.

We have returned from a week away...

Now that it has been established that there should be a bolt-in 3rd crossmember which would support the rear of the transmission, I would like to ensure that I understand what I should be looking for.

The transmission case I have is shown in the MPC as being for part number 591194, “1941-47, All Comm. (3 Speed)”. In case it makes a difference, the serial number stamped on the transmission is 6II836I with what looks like a 'Y' on its side to the left of the number.

In a previous post, Dan (Gdads51) posted a photo of a crossmember (transmission support) for sale on eBay. (I have attached a copy to this post.) Before I go off and purchase one of these, I want to make sure that it is the right fit for what I have, as we still don’t know what frame I have – would it be too long/short? Also, would it reach forward far enough to connect with the rear of the transmission? (If someone has the crossmember I need in their parts stash, let me know...because as soon as I am sure of what I am looking for, I will be placing a "Truck Parts Wanted" post in the Swap Meet forum.)

I have taken several photos and hope that someone with a ’41-’46 will see if the photos I have attached show a similar relationship between their transmission and its support.

I have seen that there are “adjustable” crossmember supports and different rear transmission support brackets that attach the transmission to the crossmember, but I am not sure that any of these are the ones I need. Photos of what is in place in trucks that use this transmission/engine combination would be welcome!

I did measure across the inside of the channels and came up with a distance of about 34 1/8”.

Also, are there supposed to be any vibration dampening components is this setup? If so, where?

That mount in the center of the crossmember in your first photo would have a rubber material for vibration dampening. Here's a picture of the transmission mount from my 1951 3100 when I recast the rubber in it. I'm assuming a mount for the 1946 would be similar or the same. Also attached is a snip from the 1929-1954 Parts Catalog for that item.

Thanks, Kevin! That helps!

I did see the listing for the "Transmission Mounting Supports" in my copy of the Master Parts Catalog, but since I was focused on trying to find the crossmember, when I saw the length stated as 6 3/4", I passed right on by as having no idea of what they were. I guess I am making progress one small step at a time.

Now, I hope to find out what the part number for the crossmember might be that would fit my project. (I have made no progress in figuring out where this crossmember would be located in the MPC.)

I have found that some new "transmission crossmembers" are available for '41- '59s through online vendors, but I would still need other components to make them work, I am sure.

The frame crossmembers are around 7.010 in the parts book. I'm not sure whether it's the third crossmember (it would be on my 1951), but I doubt you'll be able to find one using a part number. I would rely on other Stovebolters and put an ad in the Swap meet section for your needs. I'm sure someone would be able to come up with one for you.

Nick - When I can get back to my laptop tonight, I’ll see what I can find on the cross member part info.

In the meantime perhaps some of our 1941-46 1/2 ton owners can measure their transmission support cross members between the frame rails to compare with your measurements???

Nick
The measurement on my ‘46 show the distance between frame rails at the points the cross member is bolted is 34 1/4 inches.

The second measurement from the rear of the cast iron at the universal joint ball to the bolt center on the cross member is 3 1/2”.

Sorry I didn't get back on line last night Nick. Here's a bit more info I found. The 3rd cross member is listed in the 1954 Chevy Master Parts Book under Group 7.012, GM# 593947. The book unfortunately doesn't give any dimensions.

The picture I posted above of the ebay ad cross member and still attached transmission mount (still available when I checked this morning) should be the correct unit for your needs. I know the price isn't too wallet friendly, but there aren't a lot being offered.

I did find another ebay ad for a more used cross member at a much friendlier price, but it does not include the transmission mount.

A note on 46Sparky's measurement. Because the frame and mount are different widths at the front and rear of the piece, it might help if everyone measured both width point to use in comparing dimensions. The second cross member I included has pictures of it being measured at about 33-3/4" wide, but it appears the measurement is being taken at the forward (narrower) width of the piece. I'd suggest suggest measuring at both points on the frame (just ahead of and behind the 4 mounting holes) and compare.

I think you'll find yours to match the 1941-46 cross member.

Hope this provides more help than muddy waters.

Be careful that you're buying the correct one. The parts listing that Dan posted indicates the 37-46 and 47-54 are different part numbers and could be different lengths. I think the transmission mount that goes on top may be available from aftermarket vendors or from the swap meet from other Stovebolters.

Thanks all!

Just to help confuse things, the 1940 shop manual I have refers to the subject crossmember as "the second cross member" whereas the Master Parts Catalog appears to refer to it as "MEMBER, Frame Cross, Third"!

Measuring across the inside of the frame rail channels (from vertical to vertical) I got 33 7/8" at the forward pair of holes and 34 1/4" at the aft pair of holes.
The channel at those points is about 2 1/8" deep.

There are aftermarket transmission crossmembers that claim to be for '41-'54 Chevrolet trucks. (Photo attached) Does anyone have experience with one of this type?

I also am thinking that I will need to purchase a rear transmission support bracket like the one in the second photo. I have not found any suppliers for new ones of these, but there appear to be some used on the market.

I used a transmission crossmember such as your first picture, not to replace an original crossmember but to provide a mounting point for a SBC conversion using an NV3500 transmission in my 1950. While you may be able to utilize one of these it would not be anything like the original type that you are looking for.

Cruiser,

While I would prefer to use an original (or original style) crossmember if I can find one at a reasonable cost, I may have to go with the aftermarket style. (When I purchased the project, I thought I was buying a 1940 truck that needed to be reassembled...but since it turned out to be a bit of a Frankentruck, if I need to go with the modern unit, I won't be doing serious damage to the project by going with a transmission mount that would only look out of place to the careful observer.)

I assume that you are not displeased with the unit you installed in your truck?

I am not displeased with the unit I installed in my truck but I did retain the original (although modified for clearance) to provide structural support to the frame at the point where the rear mount for the front leaf springs. The cross member I retained was riveted in and may be in place on your frame (I cann't tell from the photos that you have provided).

In my case I do not believe that the original frame cross member I modified provided a transmission mount. I beleive it was used to support the bell housing but I do not recall for sure and apparently do not have any pictures of the original engine and transmission in place.

The cross member I added is only intended to provide a rear mounting point for the engine-transmission and not provide structural integrity to the frame.

Cruiser,

The frame under my project has an original-looking, riveted-in crossmember with mounts to support the rear of the engine at the bellhousing. (See 1st photo)
There are holes in the frame that seem to indicate that the bolt-in crossmember should be present, but was not when I purchased the project. (See 2nd Photo)
Although there are some measurements of my frame that don't seem to match what appears in the Chevrolet publications, it seems to mostly match the 1941-'46 frames.
The '42-'47 Chevrolet Shop Manual refers to a bolt-in crossmember "...is of box member construction for its entire length. Bolt attachment to the side members provides easy removal for the servicing of the transmission."

I'm not familiar with the 40's vintage trucks, mine is a '50 and a 3600 (3/4 ton) so I'm sure the information that I have may not be directly applicable to your situation.

However, if you have the bell housing mounting points on the riveted in cross member I don't think you want a 2nd transmission mounting point. My understanding is that the transmissions are fully supported by the bell housing and adding another transmission mount at the rear of the transmission can create a problem. However, the bolt in cross member your seeking may provide frame structure and not a transmission support. If it is behind or below the transmission making it removeable would make sense to be able to move the transmission back for removal.

Perhaps someone with more direct knowledge of your vintage truck can provide better insight.

A little late to the dance, but I matched up some pics of my '46 frame with some of your pics. My frame looks very similar to yours.

Cruiser,
Your input is appreciated. Since we have not nailed down exactly what frame I have, all thoughts are very welcome and considered.

John,
Thanks for posting the photos of your frame. With the exception of the location of some of the holes, they look very similar. What is the measurement across the outside of the frame horns at the front? Mine measures 26 7/8" there and the drawings I have found for the '41-'46 frames show 25 45/64".

I have found a crossmember and bracket though another Stovebolter and expect it to arrive at the end of next week. It will be interesting to see if it bolts right up to the existing holes in the frame! I will report back.

At the tip, outside to outside, I have 26 7/8" also.

Interesting that your frame measures the same as mine does, even though the drawings show that it shouldn't.

Maybe I should stop stressing and accept that it is a 1946 type frame.

Very reassuring.

Thanks!

I'm guessing you have the same frame as I do. I do see that you have rivets in the #2 positions and mine are empty.

Oops - I just checked and my #2 position has the bolts for the battery tray.

John,

The empty holes in your frame that you have numbered as #2 are filled with rivets that hold the battery box on my frame. (The rivets look to be original.)

I now see your "Oops".

Attached is a photo of my frame with the holes/rivets numbered to agree with yours.