Please Help !!! Any CVT Experts?

Jul 5th, 2002, 12:11

Still having problems with my '84(B) 340 CVT, the revs just do not want to drop you can't really go over 30mph without the engine screaming :-(

The low gear ratio switch in the centre console doesn't light up anymore, this might have something to do with it. I've just had it in to my local friendly volvo service agents and they can't source the problem !! (I think that they just don't have a clue to be honest) this car is in good condition and has just passed it's MOT for yet another year (these things just keep plodding on) it's only done 65,000 miles and I think there's lots more life in the old beast yet..... if I could just sort this one problem !!!!

Any help greatly appriciated.

foggyjames · Jul 6th, 2002, 09:45

im no expert, but it sound like the low gear hold is stuck on permanently. i believe this is vacuum operated, so maybe a failure?

cheers

james

Paul Clifton · Jul 12th, 2002, 22:34

Change the 4way vacuum valve under the bonnet r/h has a rubber bellows either end.Try second hand as new is arm and a leg.
Paul.

Aug 23rd, 2002, 14:17

I am a new club member and new to this forum but I know a little about the CVT system.
Remember the ratio changes are effected mechanically via weighted quadrants in the outer primary pullys - the secondary pullys are sprung loaded and simply slave to the primaries.
The vacuum system either provides upchange assistance to the mechanical system (via up side of 4way vac-valve)during acceleration or removes this assistance to give "kick down" (via 4 way and throttle cable switch)or provides positive opposition to mechanical sytem (via high pressure brake switch or low ratio hold switch and brake side of 4 way valve).
The mechanical system goes on trying to upshift all the time.
The assistance / opposition is also controlled via the tachometric relay.

If you really cannot get more than 30mph without very high revs I think that sytem is in "positive opposition" mood ie. engine vacuum is being routed to the inner chambers of the primary pullys to force the tranmission to remain in low ratio. Assuming that you do not have a mechanical seizure of one or more pullys (rare in a "daily driver")
I would suggest you look at high pressure brake switch, low ratio hold switch, tachometric relay and brake side of 4 way valve. It is essential you source a wiring diagram as the system does not follow logic (eg. kickdown switch works by removing an earth from the tachorelay).

Sorry for such lengthy first post but I hope the above helps mollusk300.

Jul 5th, 2002, 12:11	#1
Neo Guest Location:	Please Help !!! Any CVT Experts? Still having problems with my '84(B) 340 CVT, the revs just do not want to drop you can't really go over 30mph without the engine screaming :-( The low gear ratio switch in the centre console doesn't light up anymore, this might have something to do with it. I've just had it in to my local friendly volvo service agents and they can't source the problem !! (I think that they just don't have a clue to be honest) this car is in good condition and has just passed it's MOT for yet another year (these things just keep plodding on) it's only done 65,000 miles and I think there's lots more life in the old beast yet..... if I could just sort this one problem !!!! Any help greatly appriciated.

Jul 6th, 2002, 09:45	#2
foggyjames 300 Register Keeper Last Online: Apr 24th, 2024 09:13 Join Date: Dec 2001 Location: Nottingham	RE: Please Help !!! Any CVT Experts? im no expert, but it sound like the low gear hold is stuck on permanently. i believe this is vacuum operated, so maybe a failure? cheers james __________________ VOC 300-series Register Keeper '13 V70 D4 SE Lux '89 740 Turbo Intercooler '88 360 Turbo Intercooler '84 360 GLT '81 343 GLS R-Sport '79 343 DL '70 164

Jul 12th, 2002, 22:34	#3
Paul Clifton Paul Clifton Last Online: Jul 18th, 2023 15:50 Join Date: Dec 2001 Location: Wisbech View Photos By: Paul Clifton	RE: Please Help !!! Any CVT Experts? Change the 4way vacuum valve under the bonnet r/h has a rubber bellows either end.Try second hand as new is arm and a leg. Paul. __________________ Paul Clifton. A man's knowledge can never outweigh his experience.

Aug 23rd, 2002, 14:17	#4
mollusk300 Guest Location:	RE: Please Help !!! Any CVT Experts? I am a new club member and new to this forum but I know a little about the CVT system. Remember the ratio changes are effected mechanically via weighted quadrants in the outer primary pullys - the secondary pullys are sprung loaded and simply slave to the primaries. The vacuum system either provides upchange assistance to the mechanical system (via up side of 4way vac-valve)during acceleration or removes this assistance to give "kick down" (via 4 way and throttle cable switch)or provides positive opposition to mechanical sytem (via high pressure brake switch or low ratio hold switch and brake side of 4 way valve). The mechanical system goes on trying to upshift all the time. The assistance / opposition is also controlled via the tachometric relay. If you really cannot get more than 30mph without very high revs I think that sytem is in "positive opposition" mood ie. engine vacuum is being routed to the inner chambers of the primary pullys to force the tranmission to remain in low ratio. Assuming that you do not have a mechanical seizure of one or more pullys (rare in a "daily driver") I would suggest you look at high pressure brake switch, low ratio hold switch, tachometric relay and brake side of 4 way valve. It is essential you source a wiring diagram as the system does not follow logic (eg. kickdown switch works by removing an earth from the tachorelay). Sorry for such lengthy first post but I hope the above helps mollusk300.

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