DM code steering box

carnutjw

Master Mechanic
Supporting Member
Sep 17, 2017
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93
So my MCSS junkyard steering box has developed a problem, excessive play from a left to right to left transition. I found an 1986 Gran Prix in a local salvage yard, factory gauges, buckets, 305 sbc, 200r4, F+R swaybars. I assumed it would have a fast ratio steering box, so I grabbed it. Appears to be 3 turns lock to lock, found a DM stamp on the end cap. Any idea how to determine what ratio it is? I've searched here and the interweb with no results.
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
5,286
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Fast ratios are typically considered as 2.5 to 3 turns lock to lock. Exact ratio would depend on the tie-rod travel change per turn. Sounds like you found a decent box, but not quite as good as what you got as far as quickness. If super fast ratio is not that important to you, send it.

It's likely not an FE2 box because that would be the same exact part number as your MCSS box (YA box, btw). I believe those are around 2.5 turns lock to lock. The F41 box on 86 GPs are different catalog p/n than other G-bodies (casting numbers usually don't mean squat). I don't know why it would be different, but it is. Unless you know for sure, DM stamping code means something to the assembly line guy, but not much to anyone else. They went by application. And they had several different part numbers for G-body steering boxes, even if they were 800 series.
 

carnutjw

Master Mechanic
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Thread starter
Sep 17, 2017
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Went back today and snagged a couple more pieces off this GP, and there laid the (crispy, moldy) build sheet inside. It does indeed have the F41 option, but I still don't know how that translates to steering box ratio and the DM INK stamp. Hope to get the 200-4R, but lets just say this salvage yard isn't the best planned out place.
IMG_0282.jpg IMG_0280.jpg
 
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383_GrandPrix

G-Body Guru
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Sep 9, 2016
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Quebec, Canada
If you get the chance, grab the at least the front sway bar. If I'm not mistaken the F41 front bar is the biggest sway bar that came factory on these cars. I would also grab any factory braces (Grand Prix and or jounce bars) if you don't need them there's always someone looking for some.
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
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Depends if it's F41 V8 or V6. V8 front bars were thicker in most cases. At least Olds were. Pontiacs??? I dunno.

If it has F41 with the LG4 (305) then it should be the best they had. I'd get it anyway if it's not too corroded. Wait, I see it. The front sway bar code "CY" on the build sheet. Yeah, that's the fat 1.25" one. Get it if you can. Grab the mounting straps to the frame too. Bushings are everywhere, so you can get new ones.

Here's another interesting deal...the build sheet is for a 1986 model. The rear sway bar calls for a 797. Which is the factory part number AND service part number for the 22mm bar, 1005797. This part was discontinued in early 1984 before 1985 production, and was replaced with the latest bar, 10029113. Hmmm. It's odd that they used the 113 (listed on 85 442 build sheets). Maybe they didn't change the p/n in Pontiac plant? WTF? Anyway, it's the fattest bar you could get in the back. Snag that one too if possible. Again, if it's pitted to sh*te, I'd probably pass on it. Or drop it and get the sway bar mount spacers from the A-arms if nothing else. What the heck.

F41 on an 86 GP means the steery box should be p/n 7838058. Service replacement number is 7848138. Even from that, I'm still not sure of the ratio of the box. It's different than any other F41 box part number. It also comes on the base Monte Carlo NON-SS coupe (GZ with a 2.3 diesel?? They stopped the 4.3 diesel in 84??? WTF) I'm not that fluent in what 3 turns lock to lock corresponds to on a G-body. I know the desirable 2.5 turn fast ones are 12.7:1 ratio, but that still isn't the final factor. The balance valve makes some difference too, as far as the "feel" is concerned. Maybe it's a variable ratio? I have no good information on it.

Here's a brand new GM one if someone feels inclined. Only 325.00 on ebay. :) Spend that money!

GM OEM 7848138 Steering Gear | eBay

MCSS, H/O, 442, GN, or GP w/FE2 all share the same factory part number of the most sought after boxes (YA stamp on the end if it's still readable), according to the parts book (7843135).

This steery sh*t can get confusing real quick. I believe if it's 3 turns, you should be ok, maybe a slight bit mushier steering than what you have now. Only one way to really find out.

Here's where you may find the YA on a 135 box.

NOS steering box 1.jpg

NOS steering box 2.jpg
 

carnutjw

Master Mechanic
Supporting Member
Thread starter
Sep 17, 2017
339
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Got the gauge package and GP bar, and I hope to get more pieces before it's pillaged. For lack of a better term, the place is kind of a junked up shithole, and I'm gonna have to roll around in some (shallow) mud, with jack stands/cribbing to get anything from the bottom side. That's not beneath me, but not really the way I want to die. Here's the DM stamp, also indicated on the build sheet, BTW. Thanks for your help guys.
IMG_0288.jpg
 

Jim Rockford

Greasemonkey
Nov 10, 2007
230
63
Shelby,N.C.
Got the gauge package and GP bar, and I hope to get more pieces before it's pillaged. For lack of a better term, the place is kind of a junked up shithole, and I'm gonna have to roll around in some (shallow) mud, with jack stands/cribbing to get anything from the bottom side. That's not beneath me, but not really the way I want to die.
LOL kinda funny you said it that way, I had quite the same thought today at the junkyard ..lol with my smuggled in bottle jack and a widowmaker scissor jack out of the closes minivan to be able to retrieve a rear sway bar..lol
20210306_134540.jpg
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,649
113
mpls
i can't find info on the DM code or even GP steering gear info, here is a chart showing ratios available on gm cars with MC available with 14:1 on non ss and 12.7:1 for ss cars.

1968_93 Nova, Monte Carlo, Chevy II Power Steering Gears



YEAR


ALPHA CODE


APPLICATION


GEAR RATIO


EFFORT


T-BAR SIZE


TRAVEL


1968-69


AE


X-8


17.5:1


15-21


0.175 Dia


39deg


1970


AW


X-8


16-12.4:1


24-30


0.195 Dia


40deg 30min


1971-72


CH


X-8


16-13:1


0.165 Dia


38deg 45min


CL


X-8 SS


16-13:1


0.180 Dia


32deg 30min


1973


GB


X


16-13:1


17-22


0.185 Dia


38deg 45min


1974


GG


Chev II


17.5:1


17-22


0.185 Dia


38deg 45min


SV


Nova Interim


16-13:1


24-30


0.195 Dia


39deg 30min


1982-83-84


FP


Monte Carlo


14:1


17-22


0.185 Dia


39deg 15min


1985 thru 93


YA


Monte Carlo SS


12.7:1


24-30


0.204 Dia


39deg 15min






 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,649
113
mpls
Any idea how to determine what ratio it is?

HOW TO MEASURE STEERING BOX RATIO​

leebox.JPG

The steering box ratio relates number of turns of input shaft (steering wheel) to complete one turn of output shaft .

(Here is my 12.7 to 1 PS box rebuilt by Lee Manufacturing. Lee Manufacturing

You can measure steering output degrees per input turn as shown above. The rusty wire at the top of the photo is my pointer, it is held to the box by the vise grip pliers. The degree wheel is just laying there it is not bolted to the shaft but some weight on it will help it stay put.

FORMULA:

Degrees of output shaft / turns of input shaft = deg per turn

360 divided by deg per turn = box ratio.

EXAMPLE: This box has 85 degrees in 3 turns, divide the 85 by 3, which equals 28.3 degrees per input turn. 360 degrees divided by 28.3 = 12.7208 turns, which means you have the 12.7 to 1 ratio box.

In other words, you would have to turn the steering wheel 12.7 turns to make the output shaft go 1 revolution.

VARIABLE RATIO BOX READINGS

If you suspect you have a variable ratio box,, first center the steering box, make the pitman arm point towards the end plug of the box, - straight forward. back off the input shaft a half turn counter-clockwise, then begin your readings, set deg wheel to Zero, thrn the input clockwise shaft back to center, then a half turn past center, stop and read degrees.

This ratio would be multiplied by the linkage ratio to arrive at "overall ratio" at the wheel.

Here is a printable degree wheel - FREE http://www.tavia.com/free_degree_wheel.jpg
 
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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
2,594
113
Galaxy far far away
So my MCSS junkyard steering box has developed a problem, excessive play from a left to right to left transition. I found an 1986 Gran Prix in a local salvage yard, factory gauges, buckets, 305 sbc, 200r4, F+R swaybars. I assumed it would have a fast ratio steering box, so I grabbed it. Appears to be 3 turns lock to lock, found a DM stamp on the end cap. Any idea how to determine what ratio it is? I've searched here and the interweb with no results.

May just need to adjust the overcenter adjustment tighter. Through you do need to remove the box from the car to adjust it correctly.
https://www.elcaminocentral.com/threads/removing-slop-in-the-gm-steering-box.27532/
 
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