I have Insignia B sports tourer (Buick regal tourx) with diesel engine , 416 Nm (307 lb-ft) (I measured it on Dyno) and 245/45 18" wheels. When cruising long distances at 130 km/h (80mph), I have around 2300 rpm. This is 61% of my nominal rpm. Just for the cruising it is too much.
The turbo of my diesel engine is efficient till 2250rpm, cause according to its spec. the engine has its top torque band between 1750 and 2250 RPM. It means that any speed with the higher rpm than 2250 would be the moment, when the engine would work less efficient. I just have an awkward feeling driving more than 130 km h knowing that my engine is performing at lower efficiency than it is capable of and I am just burning fuel hence money for nothing. Also higher rpm cause a tiny bit more wear on the components. I maintain my car and want that it functions for a long time.
During my trips I measured the engine load with app over db2 interface. On the highway the engine has the load of only around 30%... I made a research about the brake-specific fuel consumption of the diesel turbo engines depending on load and rpm. The engines burn less fuel, if the load is at 2/3 and the rpm is relatively low. So, my aim was to lower the rpm and to increase the engine load on the highway to burn less fuel.
Those are three reasons why I am changing the final drive from 3.545 to 3.091. I calculated, at 130 km/h I should have 1950 rpm. Still in the middle of the top torque band and still it would be at 52% of engine nominal rpm (where the peak power is).
Well, honestly, even with 3.545 that car doesn't have power to accelerate quickly in the sixth gear. It accelerates slowly like a yacht. No one of the passengers feels it. So, I will not be surprised by low torque on the wheels after the rebuild.
I really hope that it would reduce the fuel consumption of the car. Diesel engines of BMW, Mercedes , VW and so on have low top gears for cruising. It means they have proved the concept.
I bought it stock with 70k km (43k miles), on highway it had 6.2 l/100km (38 mpg). Now after some mods it has 4.8 l/100km (49 mpg). I am trying to get the best efficiency on long highway trips from the car to be able to travel with clean confidence and some money left in the pocket
What 6th gear ratio do you have?
As long as a diesel is making boost, there won't be much change in efficiency from slowing it down. There will be some, but the change will not be as significant as it would be with a gasoline engine.
I have done the following: Lowered by 2.5 cm, Installed upper and lower active grille shutters and programmed them to Arduino to work on highways on light and middle engine load Installed engine underbody cover Installed underbody side covers up to the rear axle Replaced 1 muffler with original 2 muffler version. Increased diameter of exhaust pipe from 60 to 76 mm from catalytic converter up to the Y-connection of two mufflers. Straightened muffler tips Changed the fuel tank to AWD fuel tank, thanks to it I have a straight exhaust pipe without bending after the catalytic converter. Made and installed underbody covers of the exhaust pipe tunnel from the engine up to the rear axle. Made and installed smooth diffuser from the rear axle till the end of the fender. Covered the outer openings of the 18" rims, so that only some holes in the middle of the wheel are left. Put a heat shield blanket on the turbo.
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Going from 3.545 to 3.091 will cause more that 12% reduce in acceleration... so if you think it is slow now it will be even worse with 3.091 and you will have to downshift for every overtaking which for me is annoying.
Well, on the highway I overtake slow vehicles at constant speed on the second or third lane. But if I need to accelerate more than a bit, I need to downshiftnto the 5th. After the rebuild I would just downshift directly to the 4th. That is my theory yet. To be confirmed...
As long as a diesel is making boost, there won't be much change in efficiency from slowing it down. There will be some, but the change will not be as significant as it would be with a gasoline engine.
I have 0.62 in the 6th.
Interesting point. I was wondering how much fuel the car would save, but could not find an exact answer. All I know that GM /Opel have has Insignia A (Buick regal) with diesel engine in two versions: standard and EcoFlex. The EcoFlex is meant to have features for improved aerodynamics and also the 3.091 final drive with 0.62 6th. So, the engineers probably did some testing and found decide to go with it. Whether the saving would be small that I would not feel it - I hope not
I don't know the turbo diagram of my engine, but if the engine rotates outside its top torque band, then turbo is working less efficient at given rpm. That is what I think personally. I would not claim it. Also the Lower rpm are improving the efficiency by having lower piston friction due to lower piston speeds. And the piston rings seal better at high loads, so if I increase the load from 30 to 40% , a marginally effect would help to improve the efficiency.
Honestly, I am looking forward to finish the rebuild the to test it. Even if I would end up burning 0.4 l more per 100km, I would not change the gearbox so quickly back. It is a lot of effort to swap it...
I see Wasii got the diff bearing shim part #s he needed last week from Fieroguru. Like Fieroguru I scrounged up a lot of the F40 part numbers about 10 years ago from everywhere I could. Here are a couple minor additions to his handy sheet:
The differential bearings are GM & Saab part number 12788353. I got the part number and ordered my bearings from RockAuto in 2018. They were the genuine GM parts and I think they came from a GM warehouse in Lansing MI. Like a lot of parts available then for the '06 Pontiac G6 F40, the originals may NOT still be available.
The industry standard bearing size for the F40 differential is 32010 series (which is 50 mm id, 80 mm od, and 20 mm width), but the GM originals were Timken brand "P900" bearings. That "P900" designation suggests there was something special about them to provide more load capability and/or life than a generic 32010 series bearing. It might be a special roller profile (crown) to avoid loading the ends of the rollers and optimize fatigue life, or it might be a special surface finish to maximize the oil film thickness with the relatively low viscosity lubricant, or maybe the special feature is tighter than normal diameter or width tolerances to minimize the variation in fit. RockAuto and others still sell a non-Timken brand 32010X bearing at a reasonable price, for a lot of applications including the differentials in the Saab F35 and F25 transaxles, but notably missing is the Pontiac G6 or Buick Regal F40 application.
I do not know if the other tapered roller bearings in the F40 had special features or not. They were all Koyo brand from the factory. One exception that was definitely special is the rear bearing on both the upper and lower shafts. It is GM part number 12787429 and is marked "32007JR/3YD". This bearing has to locate on the end of the shaft, but also provide a wide shoulder for the adjacent (4th & 6th) gears that rotate on their needle bearings, so it has a special 28 mm cone inside diameter that is smaller than a normal 32007 series generic bearing. I got mine from a GM dealer in 2018. The 3YD suffix indicates the 28 mm id (2YD suffix would be 30 mm id, 1YD is 34 mm, and no suffix is a standard 35 mm) - all are 62 mm od & 18 mm wide. The bearing on the rear of the input shaft IS a standard 32007 bearing with 35 mm id, GM part number 12788030. I got that part number and that genuine GM bearing from RockAuto in 2018, which does not show them anymore.
Lots of folks apparently use ARP brand bolts to hold the final drive gear to the differential (M10 x 1.25, 35 mm long, as noted by Fieroguru) but the original GM part number for the differential bolts was 90541316 which is 12.9 ultra high strength with an E14 external Torx head, a 10 mm unthreaded grip length, and a prevailing torque lock patch. It has been discontinued and replaced by GM & Saab part number 55562646 which is identical except threaded full length and no lock patch. I got my 55562646 from a Saab parts dealer. Though I'd never seen them before this transmission, I've decided I really like external torx bolts. For what it's worth.
Thank you for your contributions! This information will help for sure!
I am struggling to find some shims for the differential preload. Only found a pretty expensive source. Instead of buying a package of different shims , I would like to order only one. How much would the torque preload of the differential bearing change if I use 0.1 mm thicker shim? (According to your experience). I have only 0.5Nm bearing preload instead of 1.5-2Nm. Best regards
It seems that the shims for the differential are nowhere available. I am stuck with this upgrade... Quite a pity that the car with F40 was built till 2022 and the spare parts are gone three years later. This is the politics of Stellantis by neglecting all previous Opel models..
Does anyone know an alternative to those shims? Maybe some shims that would fit from other car brands and applications? Even if it would be Boeing 747.
Differential bearing shims are used in most transaxles as well as RWD differentials. Instead of looking for the GM Part #, search for the size of shims you need.
The bearing is 80mm OD, so that or something slightly less should be the OD of the shim.
Thank you for the hint. 75 mm is really a limit I would say. I also was searching at any other car brand for shims with similar dimensions. I was wondering whether the 3rd brand shims is not hard enough to withstand the pressure during the 400nm torque application in the first and second gears.
The best one was the shim from Caterpillar! Believe it or not. I have sent a request for price. Part number 121-7399. ID 70, OD 79.5. thickness 0.05.
Hello. I am a new member with a question about the final drive swap. I have an Insignia A A20DTH ecoFLEX and form the pic fikuna45 posted it's fitted with 3,091 final drive. But I am afraid the gears are too long with this final drive. On third gear at 3000 RPM the speed is 95 km/h, on 6th gear the car doesn't have any power for acceleration at 140 km/h while cruising on the highway. And I am curious why would you all want to swap yours with a 3,091? Aren't the cars more responsive with bigger final drive ratios? Or I am missing something? Or maybe the car will be a lot better with a fine tune of the ECU?
Hi!
My car is Alfa Romeo 156 SW, 2.4 (2387ccm) JTDm, inline 5, 20V diesel engine. My car's wheels are bit smaller in diameter than Opel Insignia's (diameter difference is 635 mm vs, 678 mm) so it will need a bit more engine rpm to do the same speed as Insignia. I saw on couple youtube videos, Insignia EcoFlex 2.0 CDTI at 3000rpm in 6th gear is doing 200 km/h (196 km/h calculated). Then I calculated for my 156 and got about 185 km/h in 6th gear at 3000 rpm, so I think that is the sweet spot with 3.091 ratio for Alfa 156. Also my 156 is less heavier than Insignia.
Now at 2000 rpm I am doing 109 km/h, and with 3.091 I would get 124 km/h, while Insignia is doing 130 km/h @2000 rpm Btw, my car is slightly tuned and it is doing ~200 hp @3800 rpm and 440 Nm @2600 rpm, and it is also doing 400+ Nm from 2200-3600 rpm, 350+ Nm from 2000-4000 rpm. I am sure that engine have power and torque to spin EcoFlex gearbox.
That's the reason why I am doing this swap near in the future. Right now I have other things to do, so swapping needs to wait.
Wasii, Here's my limited iterative bearing preload/drag torque experience with my one F40 differential swap in 2021.
The original differential in my used transmission had a 1.10 mm bearing shim and the diff rotated very freely. The first time I tried assembling the same case with a new differential and new diff bearings I tried a 1.35 mm shim. 1.35 was much too tight - I was unable to rotate the diff with 60 lb-in (approx 7 n-m). To initially estimate what shim I needed I unscrewed all the case bolts 30 degrees at a time and measured the drag torque. The 1.25 mm thread pitch of the M8x1.25 case bolts suggests that each 30 degrees of rotation of the case bolts would relax the case joint approximately 0.1 mm.
After the first 30 degrees of unscrewing all the case bolts, the diff still didn't move with 60 lb-in torque applied. The second 30 degrees gave a drag torque of about 27.5 lb-in (approx 3 n-m). A third 30 degrees of bolt rotation gave about 15 lb-in (approx 1.7 n-m) which was close to what I was hoping for. In retrospect that figure is consistent with the 1.5 to 2.0 n-m spec from the Alfa service manual you found. If three 30 degree rotations gave 0.1 mm slack each, I assumed a shim that was 0.3 mm thinner than 1.35 = 1.05 would be about right for me. I didn't have a 1.05 mm shim, but I did have the original 1.10 mm shim. I assembled it with the 1.10 mm shim and got about 3 lb-in (approx 0.34 n-m) which was too loose. I bought a 1.15 mm shim and that gave me 7.5 lb-in (approx 0.85 n-m). I liked the way that felt and left it that way.
A professional transmission shop might not take the same iterative approach to get the drag torque correct. I suspect a high volume operation would choose to measure the parts one time only to determine the proper shim thickness. That would probably involve a special tool kit with precision spacers to allow reaching into the case to measure an axial gap. I saw a reference for an Opel F40 transmission overhaul tool kit # DT-46798, but I have never seen one and do not know what it included.
The Caterpillar 121-7399 shim you found sounds like a perfect diameter. Of course in addition to that 0.051 mm thick shim, It appears they also offer 0.076 mm thick 121-7400, 0.178 mm thick 121-7401, 0.380 mm thick 440-2139, and 0.599 mm thick 121-7402 in the same diameters. Good luck.
Hello, Thank you for sharing your experience. It helped me to select a correct shim quicker . After having 1.2mm shim on used differential bearing with 0.3nm preload, I have tried out 1.3 mm that resulted in 0.8nm preload. Thereafter I got 1.4mm and got between 1.2nm and 1.5nm. Since it is a used bearing for 70 000 miles on it, I left it like this.
Interesting to mention: the starting torque to overcome friction was 4.5-5nm with 0.8nm preload and 6.5 mm with 1.2-1.5nm preload torque. So be aware of that when using sensitive torque meters.
By the way, I needed to call around 6 Fiat & Alfa Romeo shops and speak even with different people from the same shop to find out the availability of the shims.
In the end I was lucky to get the fiat shims. I don't know why, but all x.x5mm shims are not available.
Now at 2000 rpm I am doing 109 km/h, and with 3.091 I would get 124 km/h, while Insignia is doing 130 km/h @2000 rpm Btw, my car is slightly tuned and it is doing ~200 hp @3800 rpm and 440 Nm @2600 rpm, and it is also doing 400+ Nm from 2200-3600 rpm, 350+ Nm from 2000-4000 rpm. I am sure that engine have power and torque to spin EcoFlex gearbox.
What would your new cruise RPM be, and can you engine and turbo combo make full boost by that RPM? If you're trying to cruise with the engine not yet making full boost, you'll certainly lose responsiveness, and may have worse fuel economy as well.
What would your new cruise RPM be, and can you engine and turbo combo make full boost by that RPM? If you're trying to cruise with the engine not yet making full boost, you'll certainly lose responsiveness, and may have worse fuel economy as well.
Hi,
My new cruise RPM would be 124 km/h @2000 rpm (6th gear) or 110 km/h @ 1750 rpm (6th gear). Turbo is GTB2056V (from alfa romeo 159 2.4 JTDm 20v 210 hp version), @1500 rpm I can get almost full boost but it takes up to 5 seconds. I get full boost 1,65 bar (23 psi) at 1750-1800 rpm (Floor it at that rpm ->wait 2-3 seconds -> full boost). Above 1900-2000 rpm, response is below 1 second. So I am confident that engine and turbo will handle new gearbox with ease. Currently I am getting around 6,5l / 100 km @140km/h @2500 rpm, instant consumption measured through OBD2 diagnostic port.
My thinking is this: If insignia which is heavier, have less powerful engine, bigger wheels is paired with this gearbox, I am sure that alfa 156 with more powerful engine, with less weight and smaller wheels will handle this gearbox easily.
General plan is to do the swap next year at some point (planning to install quaife/wavetrac diff also, but currently I am unable to do it), 'till then I will not know if consumption would decrease or increase .
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