I am wanting to replace the 4spd transmission in my 78 242 (B21a) with a 4+ o/d unit from an 80 245 (B21a) or an 86 245 (B230f).

My 242 is a solid running brick, but I find highway cruising is just tooo much of a "flight of the bummblebee."

A few questions for the board...

Do I need to have a custom drive shaft built? - or will the front shaft from the 86 compensate for the shorter space b/w the rear of the o/d unit and the rear diff??

What might I expect in the drop in final drive ratio??

(My Haynes manual is too general to provide such data.)

Any other information, experiences, or thoughts are most welcome...

Thanks in advance

From all the great input - It appears that if I take the clutchplate, 4+o/d transmission, driveshaft, and transmission crossmember from the donor car, renew rear engine seal, throw-out and center bearing - I'll be in fine shape.

What about the mating of the drive shaft to the rear diff?

I had one mechanic (later turned out to be a knowledgeable euro car ripoff artist) tell me that the four holes on the drive shaft and/or the rear diff came in two different diameters on the depending upon the year of the car.

He charged me over 1.5 hours labour because he said the if the bolts were too small for one set of holes, the side to side shear motion would eventually loosen the bolts and lead to driveshaft failure -as in the bolts breaking off.

The drive shaft had been installed by a reputable volvo repair shop - I trust them more.

I just paid my highly inflated bill ($250 estimate was $500 when I went to pick up the car) - got my car the heck out of his shop and never went back. He has since closed shop (second time in 15 years).

Was he anywheres near the truth??

Thanks for all your help on the driveshaft retrofit questions.

make sure you get the crossmember from the donor car. You need a different one for the overdrive transmission. It is possible to hammer the crap out of the original crossmember and make it fit but I really don't recommend it. (don't ask me why I know this)

Yes, the transmission input shaft splines are not the same. So make sure you get the right clutch. I replaced the transmission in my 81 242, thought I was getting a 81 transmission, but got a 79.

I pretty sure the number of splines on the trans. input shaft changed between '78 and '80. Be sure to get a clutch disk for an '80.

The shorter front driveshaft from the donor will compensate. If it fits, grab the entire driveshaft. Combining fronts and rears of different driveshafts may work but as they weren't balanced together may give vibration. Do mark the different parts so you know how they go together.

Expect about 20% drop in rpm.

While you have the tranny out inspect the clutch assembly and renew the pilot and throwout bearings. You may also want to change the rear engine crankshaft seal and the front and rear seals of the new tranny.

Bram