77 Monte Carlo Rear End

[PeteA216]

Hey again guys. My neighbor's trying ta sell me the rear end from his 1977 Monte Carlo TH-350, 305 2bbl for my 1984 TH-700R4, 305 4bbl Caprice. He claims it's got 3.08 gears, not posi though. Should I trust it? Does anybody know what gear ratio came with that year Monte? Will the entire rear end just drop right into place of mine?

[silicon212]

Originally Posted by PeteA216

Hey again guys. My neighbor's trying ta sell me the rear end from his 1977 Monte Carlo TH-350, 305 2bbl for my 1984 TH-700R4, 305 4bbl Caprice. He claims it's got 3.08 gears, not posi though. Should I trust it? Does anybody know what gear ratio came with that year Monte? Will the entire rear end just drop right into place of mine?

Doesn't your car now have 3.08s? Or is it 2.56s?

I am not sure if the 1977 A/G-car control arm layout is the same, or if the width is the same. Inasmuch as the gearing/whatnot, if you look at the front of the axle tube on the passenger side, you will see a series of letters/numbers - the factory gearing is encoded in this number. For more information, see this Nova page (the information should be the same for the same model year) - GM Axle Codes (up to 1979)

[PeteA216]

Originally Posted by silicon212

Doesn't your car now have 3.08s? Or is it 2.56s?

Well, I thought I had the 2.73 gearing with the 10 Bolt 7.5" Series 2 carrier, but now I'm doubtful. What did the '84 Caprice's w/ the 305 and 700R4 come with?

[silicon212]

Not saying this is definitely what you have, but every B-body CHEVROLET I've seen from the 80s has the G87 in it (8.5"). I've yet to see one with G89 (7.5") in it. Your '84 should have the SPID label in the trunk - look for any "G" RPO codes -

GH2 76 87 AXLE,RR 2.29 RATIO
GH3 86 88 AXLE,RR 2.77 RATIO
GH4 76 81 AXLE,RR 2.28 RATIO
GL1 76 81 DIFFERENTIAL CARRIER,RA AXLE,ALUM
GM1 87 87 AXLE,RR 2.59 RATIO
GM3 85 88 AXLE,RR 3.45 RATIO
GM7 82 83 AXLE.RR 2.39 RATIO
GM8 76 88 AXLE,RR 2.56 RATIO
GN3 76 81 DRIVER CONTROL LEVELING
GS4 85 86 AXLE,RR 3.70 RATIO
GT4 76 88 AXLE,RR 3.73 RATIO
GT5 76 88 AXLE,RR 4.10 RATIO
GT8 76 88 AXLE,H.D. RR 4.10 RATIO
GU2 76 88 AXLE,RR 2.73 RATIO
GU3 82 85 AXLE.AR 2.93 RATIO
GU4 76 88 AXLE,RR 3.08 RATIO
GU5 76 88 AXLE,RR 3.23 RATIO
GU6 76 88 AXLE,RR 3.42 RATIO
GV4 82 87 AXLE,RR 3.36 RATIO
GV8 82 85 AXLE,RR 2.72 RATIO
GW4 84 85 AXLE,RR 3.31 RATIO
GW6 85 88 AXLE,RR 3.27 RATIO
GW9 76 88 AXLE,RR 2.93 RATIO
GX3 82 88 AXLE,FRT 3.33 RATIO
GX4 76 83 AXLE,RR 3.75 RATIO
GX5 76 83 AXLE,RR 4.09 RATIO
GY5 76 87 AXLE,FRT 3.65 RATIO
G44 85 87 AXLE,RR 3.07 RATIO
G50 76 88 SPRING,H.D. RR(VAR 1)
G51 76 87 SPRING,SPL H.D. RR(VAR 2)
G52 82 87 SPRING,EXTRA CAPACITY RR
G60 76 88 SPRING,AUX
G66 76 88 ABSORBER,AIR BOOSTER RR SHK
G67 76 77 ABSORBER,AUTO LVL CONT SHK SYS
G67 78 88 ABSORBER,ELEC LVL CONT SHK SYS
G72 80 80 AXLE,RR 2.14 RATIO
G72 81 81 AXLE,RR 2.14 RATIO (EXPORT)
G72 82 87 AXLE,RR 2.14 RATIO
G75 82 87 AXLE,RR 3.62 RATIO
G80 76 88 AXLE,RR LOCKING TYPE
G83 82 83 GEAR,RING 8.75 IN
G87 76 87 GEAR,RING 8.50 IN
G88 76 83 GEAR,RING 8,875 IN
G89 76 87 GEAR,RING 7.50 IN
G92 76 88 AXLE,PERFORMANCE RATIO
G95 85 88 AXLE,ECONOMY RATIO

[GreyGoose006]

silicon, you are an absolute wealth of knowlege... as usual.

[PeteA216]

I've got the GU2 code - Quote: "GU2 76 88 AXLE,RR 2.73 RATIO" Is that still the Series 2, 7.5" 10 Bolt?

PS: Silicon, thanks for all the information, not only on this thread, but the many others in the past as well. You truly are "an absolute wealth of knowledge." How do you know all of this (curious)?

[silicon212]

To be honest, some of it I don't readily know, but I research and post what I find. At other times, I'll pick up on something from another thread and post it in my thread - such as that Nova axle link above - I lurk on almost every thread in the Chevrolet section! Either way, when I research, I learn so as not to have to research it later if the need arises.

Most of the time, I am posting what I know through experience - I've been doing the engine thing since I was 10 or so - I'm 38 now so it's been a while! Much of my experience comes from lessons learned through my own SNAFU situations - more recently my experience with the TH700R4/4L60 bears this out, but I still continue to learn what I can. I can guarantee that the next TH700R4 I do will be flawless, as much so as the parts I use in it.

I've always been a sponge for knowledge and age isn't slowing that down.

Getting back to the question at hand, you might be able to determine whether you have a 7.5 or 8.5 by looking at that Nova link again - there are some differences between the housings used between the two sizes. Look at the top of that page, Rear Axle Identification, for a general quick comparison. Again, my personal experience shows me that every Impala/Caprice 1977-1990 B-body has an 8.5" ring axle. The same experience tells me that non-Chevy B-bodies almost always have the G89 7.5" rear end.

[PeteA216]

I'll try the Nova page onec I get a chance to get under the car (tonight hopefully). I heard from somewhere (cant remember where) that only the 9C1 cars and wagons had the 8.5" with the 5 on 5 bolt pattern while civi sedans came with the 7.5" with the 5 on 4 3/4 Bolt pattern. I'll get back to you once I get some numbers off the axel.

[silicon212]

That's not entirely true on the 9C1 cars, either. Not all of them have the 5 on 5 arrangement, those could be counted on only if the car had the 5.7 engine in it before 1991. Mine came with a 305 and has the 5 on 4.75 with a 8.5" rear gear.

[PeteA216]

Oy, so many different combinations... I'll most definately get the #'s off my rear axel, and see what I can come up with.

[Blue Bowtie]

Yup. Scrape/wire brush off the right axle tube, and take along a flashlight and magnifier. They can get tough to read.

[PeteA216]

Uhh, guys, I kind of ran into a problem here. My axel (at least the tube part on both sides) is almost completely clean of rust, but even after removing most of the paint with a wire brush in the passenger front area of the tube I still couldn't find any code anywhere. Am I looking in the wrong spot?

[silicon212]

Should be on the FRONT of the PASSENGER side tube.

[PeteA216]

Alright, I finally got the numbers. The first three were kind of hard to identify, so I took some pictures with my phone and put them on the computer. I read it as: 8GB K 346. Heres one of the pictures I took:



Now my new problem is that the code doesn't seem to correspond with anything the Nova page silicon gave me has to offer. I'll buzz around the internet and see if I can find anything, but any help would be greatly appreciated.

[silicon212]

Interestingly, ignoring the 8, "GB" comes back as a 1982 Firebird 2.73:1/7.5/non-limited-slip. Looking at the other years online, disregarding the other two digits in front, a "B" at the end seems to denote 2.73:1 ratio, with a middle B (i.e. xBB) meaning limited slip. The K means GM of Canada (all pages were in agreement on this) and the 346 is the Julian date of the year the rear axle was assembled (December 12). Now if this is a 2.73:1 rear, you gain absolutely nothing by getting it, aside from a potential headache due to it possibly not fitting a B-car (the Monte is a G-car).