'73 620 4spd-5spd trans swap questions

[GRpufnstuf]

questions..

 

Is the transmission cross member different on late model truck vs 1973 620?

 

OR is it the trans mount itself? (Rock auto shows the same part number for all manual 620 mounts)

 

finally, maybe it's the transmission i used?  I think most 5spd L series trans are essentially the same outside?

 

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SO!  I bought a '79 280z trans from a local member.  It was a wrecking yard pull of unknown quality but it was cheap.

 

ANYway It's in my truck and it's no good.  3rd and 5th have terrible bearing noise and 5th pops out of gear now and then.  Plus there is a small crack in the case allowing oil to leave 

 

I'm having a local shop rebuild a different trans for me but I have a question in the mean time.

 

When i swapped from my 4spd I thought I had all the conversion and service parts lined up...

 

New rear main seal

New high pressure roadster clutch kit

already have new clutch slave and hose installed

L series 5spd

rear output seal

front half of a late model drive shaft

late model shifter cover (interior)

Chrysler door hinge kit for shifter.

straight/short shift lever of unknown vintage from eagle rock swap.

 

everything fit with 2 exceptions:

 

1.  The bell housing to engine bolts were too short from the orginal 4spd,easy fix.

 

2  The trans mount and cross member are too high?  I had to space the cross member down almost 2" to get it to fit and it still has small contact with the truck  at the vent?

I haven't checked pinion angles yet but I will when the rebuilt trans is going in.

 

 

PS.  Holy shit that bronze bushing kit for the shifter makes it feel nice!

 

PPS.  Another thing I noticed, the carrier bearing metal cage is different from '73 and '78 (the drive shaft I got)  The '78 was an inch taller and came off a longbed I believe.  I used that since I never got around to spacing my carrier up to compensate for lowering the truck.  I can't recall if that's common knowledge or not.

[red13]

The big difference i noticed were drivesahft lengths, u need one from a later year which is shorter for the long tail trans.

[datzenmike]

The 620 drive shaft is in two parts with three U joints. The front half will be either a 'long' for the '73 with the short 4 speed or a 'short'' used with '74 and up long 4 or 5 speeds.

 

Up to Sept '73 build dates the L16 and a shorter (26") F4W63 transmission was used. Oct and on are '74 model year and have the longer 31.5" F4W71B transmission.

 

The two transmission mount cross members are different but physically the trucks are the same.

 

A '74 and up driveshaft (shorter by about 5.5") to compensate for the longer transmission should work on a '73 with the longer transmission. 

 

It's imperative that the longer transmission sit at the same height as the older shorter 4 speed to keep the drive shaft angles close to the same to prevent vibration.

 

The rear drive shaft comes in two lengths to reflect the two different wheelbases. One is about 9.45" longer or shorter than the other. Wheelbase length has no effect on front driveshaft length. Only the transmission length affects the front drive shaft.

[GRpufnstuf]

i know all that Y'all

 

I already did the swap and put all that in. WHY is the transmission hitting the "tunnel"?  I wouldn't be able to get the cross member bolted up at stock height if i tried.  

 

I will be checking and correcting pinion angles when the rebuilt unoit goes in. I don't like the spacer setup but its solid if I have to use it.  I'll shim the rear spring mounts for angle correction.

[datzenmike]

The two transmission mount cross members are different but physically the trucks are the same.

You need a '74 and up cross member for correct transmission height.

[GRpufnstuf]

ha! thanks mike  

 

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