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  #1  
Old 03-21-2017, 02:34 PM
NJTy180 NJTy180 is offline
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Default Differentials, Ratios, Speeds and RPM's

I've been doing a lot of research on this forum and around the internet for the past few months learning about the diffs that came in these cars and trying to figure out what ratio would be best for my project.

The car I have the most experience driving when I was younger was the 745 w/ ZF Auto that I'm currently working on, but I don't plan on using the ZF when I put it back on the road. I would like to retain the driving/cruising characteristics that transmission provided, just with the ability to row gears.

The other two diesel powered Volvos that were in my family growing up wer a 84 244 w/ 3 speed auto? (that car sucked) and a 245 w/ M46. It wasn't until I started reading the comments on this forum did I remember how short 1st gear actually was on that trans.

I picked up my 83 760 will intentions of doing a full drivetrain swap into the 745, but I really don't think Ill be happy with the M46 and after seeing all the T-5 swaps, that got my gears turning on my own trans swap.

It's really been bugging me not knowing what gear ratios were in the 3 cars I have so today I set out to answer that question and here's what I found.



1983 760 D24T/M46
1031 Housing - 3.54 Ratio - Non-Locking

1989 745 B230FT/AW71
1030 Housing - 3.73 Ratio - Non-Locking

1985 745 D24T/ZF22
1031 Housing - 3.91 Ratio - Non-Locking

I already knew none of the cars I had were locking diff equipped, but I will hopefully remedy that in the future, the ratios were the important thing for the day, now I could calculate gear ratios, final drive ratios, speeds and RPMs based on OE tire sizes.

The ZF/3.91 combination provides the following results;
ZF Ratios - 1st: 2.48 - 2nd: 1.48 - 3rd: 1.00 - 4th: 0.73
Final Drive Ratios - 1st: 9.70 - 2nd: 5.79 - 3rd: 3.91 - 4th: 2.85
Speed @ 3000 RPM - 1st: 22 MPH - 2nd: 37 MPH - 3rd: 55 MPH - 4th: 76 MPH

The M46/3.54 combination provides the following results;
ZF Ratios - 1st: 4.06 - 2nd: 2.16 - 3rd: 1.37 - 4th: 1.00 - 5th: 0.79
Final Drive Ratios - 1st: 14.27 - 2nd: 7.65 - 3rd: 4.85 - 4th: 3.54 - 5th: 2.80
Speed @ 3000 RPM - 1st: 15 MPH - 2nd: 28 MPH - 3rd: 45 MPH - 4th: 61 MPH - 5th: 77 MPH

Now that I have some numbers to work with, I can figure out what diff will work best for me. Just figured I'd post this now because this was the information I was looking for when brainstorming the project, hopefully someone else can find it useful in the future.
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1985 745 GLE D24T ZF22 || 1983 760 GLE D24T M46 (Parts Car) || 1989 745 Turbo B230FT AW71 (Parts Car)
1993 GMC Typhoon #0180 || 1993 GMC Typhoon #1579 || 1992 GMC Typhoon #1068
2007 Chevy Trailblazer 3SS || 2001 Chevy 2500HD 4x4 || 1952 Cadillac Series 62 Coupe

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  #2  
Old 03-21-2017, 03:00 PM
ngoma ngoma is offline
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The stick shift D24Ts got the 3.31 set, no?
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  #3  
Old 03-21-2017, 04:08 PM
R.Mojica R.Mojica is offline
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No, as far as I can tell they all got the 3.54. I have a 3.31 that I want to put in mine because I do a lot of highway driving.
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85 745 TD M46 251k (white) Holset HY35, 4" turbo back, n/a intake manifold, intercooled, GTD nozzles set to 2400psi @18psi. super pumped
86 745 TD auto 254k sold
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67 122S 72k (barn find)
89 760 TIC for sale non running.
93 850 5spd 396K.
94 850 Turbo (race car) 12.55@112.4
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  #4  
Old 03-21-2017, 04:14 PM
NJTy180 NJTy180 is offline
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Quote:
Originally Posted by ngoma View Post
The stick shift D24Ts got the 3.31 set, no?
Nope. Some may exist, but clearly it cannot be assumed that they were all 3.31's. I've seen others comment on here that the factory M46 cars were 3.54's, my car supports that claim, but I haven't been back in the Volvo game to comment otherwise, just sharing my findings.

just the same, I found conflicting info on the ZF D24T's, but a majority did support the 3.91 which is what I found in my car and I know its the original rear.
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1985 745 GLE D24T ZF22 || 1983 760 GLE D24T M46 (Parts Car) || 1989 745 Turbo B230FT AW71 (Parts Car)
1993 GMC Typhoon #0180 || 1993 GMC Typhoon #1579 || 1992 GMC Typhoon #1068
2007 Chevy Trailblazer 3SS || 2001 Chevy 2500HD 4x4 || 1952 Cadillac Series 62 Coupe

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  #5  
Old 03-22-2017, 06:23 AM
R.Mojica R.Mojica is offline
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ive been running a 215/55 16 on the rear for a while now. it helps for about 2 more mph at the same revs.
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99 Ram 2500 24V Cummins 199k
85 745 TD M46 170k (silver)
85 745 TD M46 251k (white) Holset HY35, 4" turbo back, n/a intake manifold, intercooled, GTD nozzles set to 2400psi @18psi. super pumped
86 745 TD auto 254k sold
Several other current gasser Volvos.
67 122S 72k (barn find)
89 760 TIC for sale non running.
93 850 5spd 396K.
94 850 Turbo (race car) 12.55@112.4
95 850 T-5R wagon yellow 199k
04 V70R Titanium/Atacama M66 245k
04 S60 2.5T awd 255k
06 XC90 V8 305k
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  #6  
Old 03-23-2017, 06:33 AM
adamdrives adamdrives is offline
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I have the greenbook which gives all specs for 84-86 cars. It's at the shop but I believe only the NA m46 cars got the 3.31 rear end (which seems counter-intuitive) and the ZFs got the 3.73 or 3.91. I'll double check this evening.
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  #7  
Old 07-04-2017, 04:12 AM
DrSpanky DrSpanky is offline
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This may help i made a little spreadsheet to calculate speed vs rpm with different gearbox ratios and final drive options. It factors in tyre size will plot speed at a given rpm (but default every 1k rpm up to 6k rpm) and a separate bit for max speed

https://docs.google.com/spreadsheets...it?usp=sharing

its open to anyone to edit so make a copy if its any use.

anything in red is to be edited as needed and i think i have the maths correct if someone doesn't mind checking it over and if its useful take a copy.


Dan
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  #8  
Old 10-20-2017, 11:44 PM
tofufi tofufi is offline
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Apologies for bumping up an older thread, just wondered if anyone had any thoughts on how accurate the figures above are?

I've got a 740 with M46 gearbox, and it does approx 3000rpm at 70mph according to the rev counter and sat nav. It definitely has the 3.54 rear end.

My old 940 td auto had a similar reading - approx 3000rpm at 70mph.

Yet everything I read suggests that 3000rpm should be closer to 77mph.

Are the rev counters just slightly optimistic, or is it possible the diesel versions of gearboxes had different ratios? My friend had a petrol (gas) 240 wagon which was only doing 2500rpm at 70mph, made for more relaxed cruising... I'd love to get that if I could.
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  #9  
Old 10-21-2017, 06:36 PM
ngoma ngoma is offline
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Apparently the M46 had only these ratios:
Gear ratios: (1) 4.03:1 (2) 2.16:1 (3) 1.37:1 (4) 1.00:1 (5) 0.79:1

Source:
http://www.nuceng.ca/bill/volvo/database/tranny.htm

Note that the OD is a relatively high (numerically low) ratio.

I do know the M46 did get different OD pressure relief valve shim/spring packs for higher PSI for higher torque engines (D24T included).

What tires are you running?
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  #10  
Old 10-24-2017, 04:09 AM
tofufi tofufi is offline
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Thanks for your reply - both cars were/are running standard 15" wheels and tyres.



All the figures I've seen agree with your numbers - but by my calculations the car should be doing 77mph in OD/5th at 3000rpm.

Whereas it's only doing 70mph at 3000rpm if you believe my sat-nav (which seems accurate) and rev counter...
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