Any numbers in the ring gear?

 

My logic is confused. If you are completely rebuilding a trans to transplant; why not rebuild the existing one? Or, if you are so worried about the final drive, pull the diff from the original. Or, just get the same year/model.
I am assuming that if you are going through all of this your HHR is disabled.

After you switch the transmissions you will need to reset the adapt in the TCM, that should take care of the final drive issues. I would be more worried about the Speedo/Odo.

I guess the answer to the question is : count the teeth on the mating gears and do math.
According to the FREE manual in my sig a 32/38 chain result in a "final drive of 3.29" and "Effective Overall 3.91"

 

old blue- don't know. I have to look.
donbrew- I am currently still driving the car with the stock transmission. The idea was to grab a used trans since i have 182,000 on the car and swap it over and hope for the best. I snagged a lower mileage used unit and it's been sitting in my shed. I was just going to replace axle seals, etc. and swap it in. I decided to rebuild the used unit and have it ready to go then there would be no downtime.

I wanted to take my time and not rush through it. Trying to rebuild the current transmission in the car would have some pretty significant downtime beings it's my only car and i've never rebuilt a transmission before. Ordering the kit, parts that don't come with the kit, whatever else would've tied me up for weeks. The guy i bought the used trans from said it would work in my car but I was very under educated before I bought it. As I rebuilt the used unit I started learning a ton of things about the trans. I really did things in the wrong order here and have learned my lesson.

But now i've spent the money on rebuilding so there's that. REally need to try and use the rebuilt trans if I can. I know my 2009 has 3.63 fdr according to RPO code. The research i've done on the 2006 cobalt with the 2.2 ecotec claims they used 3.63 as well for automatic. The guy i got the trans from doesn't have the car anymore so can't check any RPO codes from that car so I'd like to confirm visually on the rebuilt trans what the ratio is.

I did run into an article where the guy posting said according to his Helm service manual 3.29 fdr with 32/38 teeth chain set up does give 3.91 but he also mentions another set up which is 3.05 with 32/38 chain setup with a fdr of 3.63.

I did consider swapping the differential in current transmission to the used one or just swapping all the rebuilt gearsets. This is of course assuming the one in the car has the same chain set up of 32/38. Not really how i planned it but I just want my money back out of it.

I counted the teeth on the mating gears in the differential and got 16/10= 1.6 needless to say this doesn't look right. there are two gears that mate up though so is this times 2 = 3.2

 

The 4t45 is renowned for lasting forever. You have to really abuse it to do any damage. I severely abused a 2008 and a 2011 for 300,000 miles each.
Have you considered GoOgle, bet there is a WIKI that tells all. I know the WIKI on HHR tells which years have what, Cobalt probably has it too.

 

Have i considered Google? Ha, Google is my best friend! Its just a matter of getting the right wording to find exactly what you're looking for and i haven't found that yet. It's frustrating. Sometimes it's just faster on here. Just need to know what teeth to count and the math involved. I know you divide the driven 38 by the drive 32 = 1.1875 x ring/pinion = FDR. But what is ring and pinion on that differential?

 

How about "hhr wiki" or "cobalt wiki" or 4t45 wiki" or "ecotec wiki", I got a lot with "4t45 final drive ratio"?

 

Any chance that guy still has some paperwork like a registration, insurance papers, load papers, etc., that includes the Vin? Wouldn’t hurt to ask. He could prolly even call his insurance agent and get it. With the VIN, any GM dealer could tell you what transmission the transmission part number it had.

 

VIN won’t tell you gear ratio, just the 4T45E . The RPO code sheet in the glove box has the information. And really the difference isn’t worth worrying about.

You say you rebuilt the used transmission, did you install new TCC and Shift solenoids? A new internal wire harness? Fluid transfer tubes?

 

For a particular VIN, have found the dealer can tell me the actual part number of virtually every part in the car. The part number will have a specific ratio. 4T45E is not a part number.

But an HHR seems to carry an RPO that gives the ratio.

I found here in these forums the RPO Code List (Options) thread.

https://www.chevyhhr.net/forums/gene...options-12674/

Over 2007-2011,

• FQ7 Ratio - Transaxle Final Drive 4.05
• FR7 Ratio - Transaxle Final Drive 3.95
• FR8 Ratio - Transaxle Final Drive 4.17
• FR9 Ratio - Transaxle Final Driver 3.29
• FX2 Ratio - Transaxle Final Drive 3.91
• FY1 Ratio - Transaxle Final Drive 3.63

Other RPOs specific to autos or manuals, haven‘t decoded that. But to keep the confusion complete,

• MM5 Merchandised Trans - Manual 5 Speed Provisions
• MN5 Transmission - Automatic 4 Speed, Hmd, 4T45-E
• MU3 Transmission - Manual 5 Speed, Saab, 76.5 Mm, 3.38 1St, 0.70 5Th
• MX0 Merchandised Trans - Automatic Provisions, O/D
• M86 Transmission - Manual 5 Speed, Getrag, 5T45-E, M, F23, 75 Mm, 3.58 1St, 2.02 2Nd, 1.35 3Rd, 0.98 4Th, 0.69 5Th

These RPO are for various year HHRs.

REMINER - As always, RPO codes don’t always mean the exact same thing across models and years. They could mean something different in a Cobalt, for example, and that could depend on the year. Familiar to readers here is the notorious example of FE5, which on a pre-2008 Cobalt is VERY different than a 2008-2010 Cobalt or HHR.

The cobalt community likes to talk about F23, F35, and F40 manuals, but I’ve never heard of them as actual RPO codes on HHR, even tho by F35 they mean the turbo manual, and F23, the non-turbo manual. By F40, they mean the 6-speed manual in later Buick Regals, and others. I have no idea if those number are ever used as actual RPO codes. (Note the F23 mentioned in the M86 description above.)

 

My RPO code MN5 shows automatic transmission 4T45E and FX2 3.91 gear ratio. It is all great information. but at the end of the day, the difference is minimal.