would the ratio of a M21 make much of a difference to a 253
would the ratio of a M21 make much of a difference to a 253
They have a taller first gear but they all have a 1:1 top gear. So it depends on your diff ratio. 3.55 was standard with M20 on a 253.
It all depends on what sort of driving you are doing.
There is a thread I think Byron put up here with all the ratio combinations somewhere.
3.55 is only std in HX-HZ. HQ-HJ are 3.08 behind 253 M20. M21 is too tall in 1st for 253 if taller than 3.55 is used with std tyres
yes thats what i thought, the car has a 3.55 and currently has trimatic, at 100kms it revs at 32-34 rpms.currently thinking about best combinations of gearbox and motors or just keep it original or 308 T400 3.08 LSD a good combination what do you think.
To be honest, unless it is original as TH400 I'd run a 308 and late trimatic (like VL). 308 with M21 is nice with 3.36, bit too tall as 3.08.
It depends what sort of driving you are doing. I reckon 3.08 is awesome for highway and my brothers red wb with 3.08 flogs my wb with 3.36 around town, which goes against logic. You can rev the 3.08 out so much further between gear changes and that is where the gain is.
the car is plated as L32 M20 i am restoring the car for sunday club day driving would original spec be better? your right i had a HX ute which had a late tri and 308 and 3.08 it was a great highway car with 205 tyres great ute.
I suppose it depends on what the original diff ratio was? 3.36 is a good compromise for what you are doing I reckon behind 253 with M20.
Wasn't the 3.36 a performance option for the LC 253 in HQ's? The ute I have is definatley 3:36 optioned and I have information from another site that this was the standard option for the HC 253 HQ's. The 3:55 diff was another performance option on this model.
THe 3:08 was an economy option for the 308 HQ's and the 3:36 was standard spec.
Also lists the following ratios for what i assume are M20 and M21 boxes.
• Manual Transmission (4 speed on 6 cylinder and 253 V8):
o 1st: 3.05:1
o 2nd: 2.19:1
o 3rd: 1.51:1
o 4th: 1.00:1
o Reverse: 3.05:1
• Manual Transmission (4 speed for 308 V8 and optional on 253 V8):
o 1st: 2.54:1
o 2nd: 1.83:1
o 3rd: 1.38:1
o 4th: 1.00:1
o Reverse: 2.54:1
3.08 was always the standard diff with 253 and M20 in almost all HQ and HJ, there is no economy axles listed (except where 3.55 is standard eg 253 M20 HJ LS). 3.55 was standard in HX and HZ for the same engine/box. HQ had 3.36 as standard if 253 and M21 was ordered, but GMH obviously realised this as a mistake as HJ-HZ got 3.55 with 253 and M21. All of this is reflected in the vehicle ID I have recorded. Rarely do vehicles have diff ratios other than what is standard. I don't think you could get 253 and M21 on commercials though, only on passenger vehicles.
3.36 was always standard with 308 and M21 in HQ-HZ.
There was also the M22 which was the standard box on HQ 6cyl commercials and optional on all other HQ 6cyl. Also fitted to many HJ-WB tonners. Ratios are:
3.74:1
2.68:1
1.68:1
1:1
3.74:1
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
Bookmarks