Series V 3.89 differential

[DougCoad]

I had the tach calibrated for v6

911tr8r
First thing to do is check the accuracy of your tach - it is 50+ years old and they are known to loose calibration. My tach was reading approx. 500rpm high. Next question: do you have a 4:22 or 3:89 rear? Easy test is to jack 1 rear wheel off the ground and put tape on both the drive shaft and the tire. turn the drive shaft 2 complete revolutions. Your tire should either slightly more (3.89) or slight less (4.22) than 1 revolution. If you have a 4:22 you can swap in a 3:89 (or 3:70 if you can find one). If you have bolt on wheels consider moving up to 14" wheels. Ford Mustang/Fairmont used the same bolt pattern. I originally had a 4:22 and 165/80-13 tires. Moving to a 3:89 and 165/80-14 tires made a big difference.

 

[DougCoad]

I had the tach calibrated for V6. The rear gears are 3.89. Tires are 195 /60 /14.

 

[todd reid]

I found a rpm/speed calculator on line. Assumptions: 3.89 rear, 1.00 top gear, 23.2 tire diameter (looked up on line - should be close), 60 mph = 3380 rpm. If you are seeing 4,000 rpm at 60mph it would appear that either your tach or speedometer (or both) are out of calibration. The speedometer can easily be checked with waze or similar GPS program.

 

[todd reid]

If it's not bother a picture may help. Did you use stock oil cooler or after market.

stock Series V oil cooler used.

 

[DougCoad]

Wow thanks for the info. I think that's about where I'm at on the tach currently .

 

[DougCoad]

I found a rpm/speed calculator on line. Assumptions: 3.89 rear, 1.00 top gear, 23.2 tire diameter (looked up on line - should be close), 60 mph = 3380 rpm. If you are seeing 4,000 rpm at 60mph it would appear that either your tach or speedometer (or both) are out of calibration. The speedometer can easily be checked with waze or similar GPS program.

Another words around 3380. Definitely not 4000.

 

[Barry]

I found a rpm/speed calculator on line. Assumptions: 3.89 rear, 1.00 top gear, 23.2 tire diameter (looked up on line - should be close), 60 mph = 3380 rpm. If you are seeing 4,000 rpm at 60mph it would appear that either your tach or speedometer (or both) are out of calibration. The speedometer can easily be checked with waze or similar GPS program.

Don't know where you found your "online calculator", but it is clearly using the calculated tire diameter rather than the loaded rolling diameter or the loaded revolutions per mile. An inflated 195/60-14 tire has an unloaded diameter of about 23.2", but the loaded rolling diameter is about 22.5" which equates to about 895 tire revolutions / mile. As Casey Stengel said, "You could look it up".

The correct engine speed at 60 MPH with 195/60-14 tires, a 3.89:1 rear gear ratio and a 1.00:1 transmission ratio is about 3,490 RPM. Still nowhere near 4,000 RPM, but also not 3,380 RPM.

 

[DougCoad]

THanks for the heads up.

 

[DougCoad]

Don't know where you found your "online calculator", but it is clearly using the calculated tire diameter rather than the loaded rolling diameter or the loaded revolutions per mile. An inflated 195/60-14 tire has an unloaded diameter of about 23.2", but the loaded rolling diameter is about 22.5" which equates to about 895 tire revolutions / mile. As Casey Stengel said, "You could look it up".

The correct engine speed at 60 MPH with 195/60-14 tires, a 3.89:1 rear gear ratio and a 1.00:1 transmission ration is about 3,490 RPM. Still nowhere near 4,000 RPM, but also not 3,380 RPM.

Once I get the engine installed I will double check

 

[Barry]

THanks for the heads up.

Doug,

I will be glad to provide you with my spreadsheet that lets you play "what if" with tire sizes, rear axle ratios, transmission ratios, cruising speeds, cruising RPM's, etc. You can let the spreadsheet calculate the tire diameters and revolutions per mile or you can simply plug in the tire makers revolutions per mile figure. If you are interested, send a Private Message (PM) to me with your e-mail address and I will send the spreadsheet to you as an e-mail attachment.

 

[Shannon Boal]

Doug,

I will be glad to provide you with my spreadsheet that lets you play "what if" with tire sizes, rear axle ratios, transmission ratios, cruising speeds, cruising RPM's, etc. You can let the spreadsheet calculate the tire diameters and revolutions per mile or you can simply plug in the tire makers revolutions per mile figure. If you are interested, send a Private Message (PM) to me with your e-mail address and I will send the spreadsheet to you as an e-mail attachment.

Barry, have you got factors for transmissions, like T-5, toyota?

 

[todd reid]

stock Series V oil cooler used. Sorry, not a great picture - you need two pieces: 1. An oil filter adapter that screws onto the block in place of the oil filter (you can barely see low on the block in picture). 2. A remote oil filter Bracket (mine is installed next to coil on fender, but you can put it wherever you want. If you google "remote oil filter kit" you should get some good pictures. Then all you need is hoses to connect it all up. Run the filter return though the cooler instead of directly to the block. You can use 90 degree fittings if necessary - hoses only bend so far before they kink. Good Luck! TR

 

[Barry]

Barry, have you got factors for transmissions, like T-5, toyota?

Shannon,

There are dozens (maybe hundreds) of potential transmissions out there. Adding that many look-up tables would require a LOT of research and would turn a simple one-page spreadsheet into a monster.

A google search for "Toyota 5-speed transmissions" or "Toyota 5-speed transmission ratios" should quickly provide relevant information that can easily be entered into a spreadsheet.

 

[DougCoad]

Doug,

I will be glad to provide you with my spreadsheet that lets you play "what if" with tire sizes, rear axle ratios, transmission ratios, cruising speeds, cruising RPM's, etc. You can let the spreadsheet calculate the tire diameters and revolutions per mile or you can simply plug in the tire makers revolutions per mile figure. If you are interested, send a Private Message (PM) to me with your e-mail address and I will send the spreadsheet to you as an e-mail attachment.

View attachment 29120

Thanks Todd

 

[911tr8r]

I had the tach calibrated for v6

I had the tach calibrated for v6

Hi guys: I already have 195.55.15 four bolt pattern and just want to know if the gears from a Mustang2 or Capri fit into the Alpine housing or do I have to do what trans shop says and install Dana rear end.

 

[Bill Blue]

What are you thinking, install ring and pinion or the whole pumpkin? Installing the pumpkin sounds more doable, but my opinion counts for nothing, not for me. I am not aware of anybody trying either and am unaware of anything that suggests it is a viable swap, but that should not stop you from trying.

Bill

 

[Barry]

Hi guys: I already have 195.55.15 four bolt pattern and just want to know if the gears from a Mustang2 or Capri fit into the Alpine housing or do I have to do what trans shop says and install Dana rear end.

911tr8r,

What makes you think that gears for a Bobcat, Capri or Mustang II will fit in a Series Alpine rear axle housing?

 

[husky drvr]

just want to know if the gears from a Mustang2 or Capri fit into the Alpine housing

911tr8r,

I would seriously doubt if any of those gears would fit and work in the Rootes axle, and for the same reason Ford rear gears wont fit in a Chevy rear end. They have no common connections from the drawing board to the final assembled product. The European Capri -Mk I and II - even if the same design as the UK Ford axle will have been machined and built as a metric unit. I know the hardware was all metric. The Pinto, Bobcat. and Mutt II that used the 6.75 inch Ford unit were almost certainly based on the European axle design but probably updated to be machined and assembled with American machines and tooling - that would include part selection for domestic sourcing. The Rootes ring gear I measured is 6.875 inch. Begins with that difference and a dearth of parts support for any of these obsolete designs.

The next issue is the Rootes design utilizes a carrier housing like the US Ford 8 and 9 inch rears that are removable as an assembly from the axle housing. All the Ford axle housings are of the Salisbury design with the gears assembled into the full axle housing and aren't removable without disassembly. It may not make a difference for pinion and ring gear design but probably is a difference factor.

If you want to figure out if any of those gear sets might fit the Rootes carrier, these are the two measurements which must match to within a thousandth or two between Rootes carrier and gear set design. First is the dimension between the pinion centerline and ring gear mounting face on the carrier. The second is the vertical distance between pinion centerline and the centerline of the mounted ring gear. If these two dimensions don't match, the gears will not interchange. IIRC, the Rootes gears are adjusted for mesh with shims, while the Ford axles use a crush sleeve to adjust mesh. As a guess, I think that would require the Ford pinions to be physically longer the the Rootes pinion.

Now that I've rained on your parade, if you can locate a Mk I Capri rear axle from a 2000 (two Liter) it is almost exactly the same size as the Alpine axle, carries a 3.44:1 gear set, has brakes that are almost identical to the Alpine - except Metric, and is the same bolt circle as the Alpine. If you are willing to do the Metal surgery to make it fit, drive shaft, spring pads and shock mounts, that would be a simpler project.

A word of caution though, even going just that low, numerically, with the gearing might cause a condition while driving that you feel the need to frequently drop out of fifth gear because you are down on revs. When the "Dark siders" started using the Rootes rears, most found the 3.89 gears very tractable while driving. My advice is to install hardened keys in your hubs, check the carrier bolts while the axles are out, and drive your Alpine that way until you decide a change is required.

Hope this helps,

 

[Aladin Sane]

I did the Dana conversion for my v8 project. It requires obtaining the correct rear end from a postal jeep with the gear set you want. I chose 3.07, but that would not be ideal for your project. You have to transplant the spring perches and shock mounts from the rootes rear to the Dana, and machine the axle flanges while converting from a 5 bolt pattern to a 4 bolt. While I was at it, I went ahead and swapped in disc brakes. It can be done, but not sure you need to.

 

[DougCoad]

Hi guys: I already have 195.55.15 four bolt pattern and just want to know if the gears from a Mustang2 or Capri fit into the Alpine housing or do I have to do what trans shop says and install Dana rear end.

Not sure what you're wanting to accomplish. But have you thought about putting a limited slip differential in?